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ENGINEERING MANUAL 
CHAP. I
1 and 2) ~ FOR MILITARY CONSTRUCTION MAY 1953 
SU"RSEDING CHAP. 1, DEC. 46 
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ELECTRICAL DESIGN 
ELECTRIC POWER SUPPLY AND DISTRIBUTION 
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DEPARTMENT OF THE ARMY 
CORPS OF ENGINEERS 
OFFICE OF THE CHIEF OF ENGINEERS 

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ENGINEERING MANUAL PART VI MILITARY CONSTRUCTION ELECTRICAL DESIGN 
May 1953 
S.peroedinc CRAP. I, Dee. 46 
Chapter 1 
ELECTRIC POWER SUPPLY AND DISTRIBUTION 
GENERAL 
1-01 SCOPE 1-02 STANDARDS 1-03 DESIGN PROCEDURE 1-04 INSTALLATION 
ELECTRIC POWER REQUIREMENTS  
1-05  GENERAL  
1-06  MAXIMUM DEMAND  
1-07  CONSUMPTION  

EI.ECTRIC POWER SUPPLY 
1-08 GENERAL 1-09 SELECTION OF POWER SUPPLY 
a. 
Adequacy 

b. 
Reliability 


c. 
Rates 1-10 RIGHTS-OF-WAY FOR SUPPLY LINES 1-11 SUBSTATION 

a. 
Ownership 

b. 
Type 

c. 
Capacity 

d. 
Transformers 

e. 
High-voltage switchgear /. Low-voltage switchgear 

g. 
Voltage regulators 

h. 
Power company's meters 


i. 
Protective provisions 1-12 SWITCHING STATION 1-13 EMERGENCY POWER SUPPLY 

a. 
Fuel 

b. 
Speed 


GENERATING PLANTS 1-14 GENERAL 1-15 TYPE 
a. 
Units of less than 20 kilowatts 

b. 
Units of 20 to 50 kilowatts. 

c. 
Units larger than 50 kilowatts in plants of less than 7,500 kilowatts 


I 

d.  Plants of 7,500 to 15,000 kilowatts  
e..  Plants exceeding 15,000 kilowatts  
1-16  CAPACITY  
1-17  NUMBER OF GENERATORS  
1-18  PARALLEL OPERATION  
1-19  VOLTAGE RATING  
1-20  FREQUENCY  
1-21  BUILDING  
1-22  FOUNDATIONS  
1-23  FUEL STORAGE  

AERIAL ELECTRICAL DISTRIBUTION AND STREET LIGHTING SYSTEMS 
1-24 GENERAL 1-25 POLE LINES 1-26 PRIMARY CIRCUITS 1-27 SECONDARY CIRCUITS 1-28 VOLTAGE DROP 1-29 TRANSFORMERS 1--30 GUYING 1--31 SERIES STREET LIGHTING SYSTEMS 1--32 MULTIPLE STREET LIGHTING SYSTEMS 1-33 STREET LIGHTING UNITS 
UNDERGROUND ELECTRICAL DISTRIBUTION AND STREET LIGHTING SYSTEMS 
1--34 GENERAL 1-35 DUCT LINES 1--36 MANHOLES 1--37 PRIMARY CIRCUITS 1--38 SECONDARY GIRCUITS 1--39 VOLTAGE DROP 1-40 TRANSFORMERS 1-41 STREET LIGHTING SYSTEM 1-42 STREET LIGHTING UNITS 
FLOODLIGHTING OF AREAS 
1-43 GENERAL 1-44 WIRING SYSTEMS 1-45 LIGHTING UNITS 
a. 
Open storage areas 

b. 
Paved areas around swimming pools 

c. 
Airplane service aprons 

d. 
Service areas at filling stations 

e. 
Loading platforms 

f. 
Parking areas at theaters, etc. 


PROTECTIVE LIGHTING SYSTEMS 
1-46 GENERAL 
a. 
Protection against intrusion 

b. 
Protection against escape 


II 
1-47 1-48  c. Guard towers d. Airfields WIRING SYSTEMS PROTECTIVE LIGHTING UNITS a. Bowl refractor luminaires b. Fresnel lens luminaires c. Floodlights d. Searchlights  
DESIGN ANALYSIS  
1-49 1-50  GENERAL REQUIREMENT SCOPE  

III 

E. M. PART VICHAPTER 1May 1953 
Part VI 
ELECTRICAL DESIGN 
Chapter l 
ELECTRIC POWER SUPPLY AND DISTRIBUTION 
GENERAL 
1-01 SCOPE. The following instructions and information are intended to serve as aguide in determining the major requirements for electric power supply, substations, electricaldistribution systems, and exterior lighting systems. Where special conditions and problems
are encountered, which are not specifically covered by these instructions, good engineeringpractice should be followed. 
1-02 STANDARDS. The current regulations of the National Electrical Code, The American Institute of Electrical Engineers, The National Electrical Manufacturers Association,The American Standards Association, and The National Electrical Safety Code (Bureau ofStandards) will apply to equipment and construction, where applicable. Departures therefrom will be permitted only when necessary to conform to the standard voltage, frequency,
equipment, and construction methods used by the power company serving the project, providing the latter are considered acceptable. 
1-03 DESIGN PROCEDURE. Investigations relating to electric power supply for aproject should be made simultaneously with the development of the site plan. Power companies serving the area should be contacted at an early date in order to determine the
availability of an adequate supply of electricity for the project and the lowest applicable
rates. Assistance of the power company's engineers should be solicited in the preparation
of preliminary power studies and in the final design of the electrical system in order thatthe equipment will, as far as practicable, be similar to that used in the vicinity. Thisprocedure will permit the utilization of the ·power company's personnel familiar with theequipment in cases of emergency. Assistance of the Army Power Procurement Officer shouldhe solicited in connection with the selection of rate schedules. 
1-04 INSTALLATION. The criteria contained in this chapter pertain to the generaldesign of electric power supply and distribution systems. For details covering materials,equipment, and installation, reference should be made to the following specifications:CE 303.03 Electrical Unit Substation.CE 303.04 Electrical Conventional Substation.CE 303.05 Electrical Switching Station.CE 303.06 Underground Electrical Distribution and Street Lighting System.CE 303.07 Aerial Electrical Distribution and Street Lighting System.CE 303.08 Protective Lighting System.CE 303.14 Generating Plant, Diesel-Electric. 
1 
E. M. PART VI CHAPTER 1 May 1953 
ELECTRIC POWER REQUIREMENTS 
1.05 GENERAL. In order to select a suitable power supply, to specify the proper equipment, and to compute the cost of electricity for the project, it is necessary to determine the approximate maximum demand in kilowatts and the average consumption of energy in kilowatt hours. 
1.06 MAXIMUM DEMAND. The most accurate means of estimating the maximum demand is to determine the connected load and apply suitable diversity factors. These factors are based on experience with projects similar in character and size to that under consideration. A break-down of large projects and a classification of the types of service required may be helpful in estimating the total maximum demand and in applying the data obtained from other projects containing facilities of similar nature but not necessarily the same size and composition. In general, the maximum 30-minute demand for the entire electrical system at posts, camps, and airfields will be approximately 30 percent of the total connected load and at storage depots will be approximately 200 kilowatts per million square feet of warehouse area. For industrial plants; the maximum demand should be determined from data furnished by the using service. On a per capita and bed basis, the following demands will be sufficiently accurate for preliminary estimating purposes: 
Army Camps..................------------------------------------------------------------------------------------------------------------------------0.3 kw. per capita. Air Force Tactical Bases________________________________________________________________________________________________________ 0.3 kw. per capita. Air Force Strategic Bases.................-------------------------------------------------------------------------------0.3 kw. per capita. Research and Development Bases ________________________ -------------------------------------------------------1.3 kw. per capita. 
Technical Schools ________ n·-----____________ . _____________________________________________ -------------------------0.6 kw. per capita. 
Repair Schools_____________________________________________________,____________________ ---------------------------------------------------------1.5 kw. per capita. 
Hospitals ___________ --------------------------------------------------_______________________________ --------------------------------------------------2.0 kw. per bed. In applying the above figures to a specific project special applications must be considered. Where other than normal loads are to be supplied, allowances must be made for the demands that will be imposed by these loads. 
1-07 CONSUMPTION. The average monthly consumption should be computed by multiplying the maximum demand by a suitable load factor and by the number of hours the facility will be in operation during the month. The load factor will usually be between 30 and 45 percent at posts, camps, airfields, and storage depots. For instance, at an Army post having a total connected load of 8,000 kilowatts, the estimated maximum demand would be 8000 x .30 = 2400 kilowatts. Using a load factor of 45 percent, the estimated average monthly consumption would be 2400 x 0.45 x 720 = 777,600 kilowatt-hours. Simihirly, using the per capita basis, at an Army post having an authorized strength of 8,000 men, the estimated maximum demand would be 8000 x 0.3 = 2400 kilowatts. Again using a load factor of 45 percent, the estimated average monthly consumption would be 2400 x 0.45 x 720 = 777,600 kilowatt-hours. 
ELECTRIC POWER SUPPLY 
1-08 GENERAL. For the purpose of this manual the electrical power supply is defined as the transmission lines, main substation or switching station, and other devices and equipment necessary to deliver energy to the distribution lines at the project. 
2 
E. M. PART VICHAPTER 1May 1953 
1-09 SELECTION OF POWER SUPPLY. The following factors should be consideredin selecting a power supply :
a. Adequacy. The first consideration should be the capability of the power company'ssystem to furnish power having proper characteristics in the required quantity.
b. Reliability. The supply should have a degree of reliability which the project warrants. Except for small posts and camps having a population of less than one thousand,duplicate supply lines should be installed wherever this type of service will be made availableby the power company without excessiy~ cost to the Government. To be of any value ininsuring' an uninterrupted supply of electricity t: •the project, the tw:o supply lines shouldbe fed from different sources, over different routes.
c. Rates. All electric service rate schedules applicable to the project should be carefully reviewed and checked with the estimated demand and consumption to insure thesupply of electricity at the lowest available rate. Care should be taken to see that the scheduleselected compares favorably with those of any other power companies serving the areaand that the rates are no higher than those paid by other customers for similar service.Where a connection charge is made by the power company an agreement should be workedout, whenever practicable, whereby the amount paid by the Government for such connectioncharge will be recovered by deducting a certain percentage each month of the total bill orby a fixed annual or monthly refund. 
1-10 RIGHTS-OF-WAY FOR SUPPLY LINES. The power company will procure allrights-of-way outside the limits of the Government reservation. The Government will grantthe necessary rights-of-way and license for the installation and maintenance of powercompany's facilities within the reservation. Power company's facilities within the reservationshould be located to avoid any interference with the activities of the project. 
1-11 SUBSTATION. Where the supply voltage is 13,800 volts or less, this voltage shouldbe usea for the distribution system throughout the project. Where the supply voltage isin excess of 13,800 volts, a substation should be provided to reduce the supply voltage toapproximately 13,800 volts for the distribution system. Substations having a secondaryphase-to-phase voltage of less than 12,000 volts will not be provided unless specificallyauthorized by the Office of the Chief of Engineers.
a. Ownership. The substation should be installed and maintained by the Governmentonly when rate schedules or primary discounts indicate that the cost of the substation will beamortized in 20 years or less by reason of the purchase of electricity at the substationprimary voltage in lieu of the substation secondary voltage. Otherwise the substation shouldbe owned and operated by the power company. Exceptions may be necessary where theload is too small for the power company to justify a substation. 
b. Type. The type of Government owned substation should be selected in accordancewith the requirements of the project, due consideration being given to planned expansion.In general, a conventional-type substation should be installed where the estimated maximumdemand is not expected to exceed 2,000 kilovolt-amperes. Figures 1 and 2 show typicalarrangements of conventional substations, using 3 single-phase transformers and 2 threephase transformers, respectively. Where the estimated maximum demand is expected toexceed 2,000 kilovolt-amperes, the substation should be either of the conventional type orof the unit substation type, depending upon the results of cost comparison and local requirements. Figures 3 and 4 show typical arrangement of unit substations for aerial and underground systems, respectively. In no case should the substation comprise only 1 three-phase 
3 
E. M. PART VI CHAPTER 1 May 1953 
transformer, as failure of this transformer would result in a complete outage ot the distribution system. Wherever practicable, manufacturer's standard unit steel structures should be utilized. Where special structure design is required, the criteria in NEMA Publication No. 49-144, Part V, should apply. 
c. 
Capacity. The total combined capacity of all transformers in the substation should be approximately 110 percent of the estimated maximum demand, consideration being given to planned expansion for which a definite program has been established. This capacity will permit normal growth of the distribution system and will insure a supply of electricity to at least one-half of the load in the event of the failure of one transformer. In order to provide service to a portion of a distribution system served by wye-connected transformers, with one transformer out of service, it will be necessary to utilize 2 three-phase transformers in the substation rather than 3 single-phase transformers. In view of the recent improvement in transformer design and construction, the installation of spare transformers or of sufficient transformer capacity to carry the entire load with one transformer out of service is not considered necessary. 

d. 
Transformers. The substation transformers should be of the outdoor, oil-insulated type and of applicable self-cooled rating selected from table I. Where required sizes are not listed in the table, the next larger size should be installed unless the next smaller size will provide at least 90 percent of the required rating. For instance, the transformers for a camp, airfield, storage depot or other facility having an estimated maximum demand of 3,000 kilowatts and an estimated power factor of 80 percent would be selected as follows: 


Example: Estimated maximum demand (3,000 kilowatts), divided by the estimated power factor (0.80), multiplied by the capacity factor given in paragraph 1-llc above ( 1.1), gives a total of 4,125 kilovolt-amperes as the most desirable rating of the transformer bank. Referring to Table I it is noted that the next smaller standard rating comprises three 1,250 kilovolt ampere single-phase or two 2,000 kilovolt ampere three-phase transformers. Either of these banks would provide 90 percent of the required rating and would be suitable for the project. 
Table I. Transformer Kilovolt-ampere Ratings 

Single-phase  
3  167  2,000  16,667  
5  250  2,500  20,000  
10  333  3,333  25,000  
15  500  4,000  33,333  
25  667  5,000  
37lh  833  6,667  
50  1,000  8,333  
75  1,250  10,000  
100  1,667  12,500  
Three-phase  
9  225  2,000  10,000  
15  300  2,500  12,000  
30  500  3,000  15,000  
45  750  3,750  20,000  
75  1,000  5,000  25,000  
112lh  1,200  6,000  30,000  
150  1,500  7,500  37,500  
50,000  

4 

E. M. PART VI CHAPTER 1 May 1953 
e. High voltage switchgear. Switchgear for use on lines having a voltage rating in excess of 15,000 volts should consist of horn gap switches and high tension fuses, provided the system-interrupting requirements can be met. The system interrupting requirements are determined by the capacity of generators and ratings of motors connecte.d to the power company's lines and the total reactance in the circuits to the point of application of the switchgear, and should be obtained from the power company serving the project. In general, fuses should be installed where the system-interrupting requirements do not exceed the values given in table II. Where the system-interrupting requirements exceed the values given in table II, circuit breakers having the required interrupting capacity should be 
installed. 
Table II.  System-Interrupting Requirements  
Line voltage  Interrupting requirements  
(kilovolts)  (kilovolt-amperes)•  
15.1 to  23.0.... .  250,000  
23.1 to  34.5.......  625,000  
34.6 to  46.0....  715,000  
46.1 to 138.0..........  1,000,000  

*Where the interrupting requirement is expressed by the power company in amperes. 
the equivalent three-phase kilovolt-ampere rquirement may be determined as follows: 
Equivalent KVA =Interrupting Current X Operating Voltage X 1.73 
1.6 
Where 1.6 =factor for offset wave of short circuit. 
f.. Low voltage switchgear. Switchgear for use on lines operating at 1,000 to 15,000 volts should consist of frame-mounted outdoor circuit breakers or cubicle-mounted circuit breakers for conventional substations and metal-clad switchgear for unit-substations. The 
interrupting requirement for the secondary circuit breakers is much less than that for the primary switchgear due to the reactance of the transformer. In general application the interrupting requirement in amperes should be determined as follows: 
KVA X 1000 X 100 I= X 1.25
V X 1.73 X (X) 
Where I = Sustained short-circuit current in secondary side of transformer (see note 1 below). KVA = Rating of three-phase transformer or transformer bank. V = Secondary voltage. 
(X) -Percent transformer reactance (see note 2 below). 
1.25 = Allowance for average d-e component. 
Note 1. Where desired, the interrupting requirement in amperes may be converted to KV A in the manner set forth above for primary switchgear. 
Note 2. For transformers 500 KV A and larger the percent reactance may be assumed to be equal to the percent impedance. For installations where the reactance and impedance are unknown, a reactance of 4 percent for substation transformers smaller than 500 KVA and 5 percent for substation transformers 500 KV A and larger will ~e sufficiently accurate for determining the required interrupting capacity of thP. secondary
circuit breakers. 
Note 3. The above formula is based on unlimited capacity on the primary side of the transformers, Where 
the system contribution is known to be 500,000 KV A or less, some reduction may result in the interrupting requirement of secondary breakers by referring to tables and formulae contained in AlEE publication entitled "Electric Power ~istri.bution for Industrial Plants." 
5 


E. M. PART VI CHAPTER 1 May 1953 
g. Voltage regulators. Voltage regulation should be provided in the substation when the voltage regulation in the incoming supply exceeds plus or minus 5 percent. Vo!tage regulation in unit-substations is accomplished by automatic tap-changing-under-load regulators mounted directly on the transformer and this type of regulator should be included in the transformer specifications where regulation is required. Voltage regulators for conventional substations, where required, should be of the three-phase, step type, and should be installed for regulating the bus voltage, rather than the voltage of individual feeders. Exceptions to this arrangement will be necessary in those cases where the regulator capacity required exceeds the capacities listed in table III. Bypass disconnecting switches should be installed in the regulator circuit in order to permit inspection and repairs without prolonged interruption of electric service to the distribution system., Figure 5 shows a typical installation of a voltage regulator in a conventional-SUbstation. The kilovolt-ampere rating of voltage regulator should be approximately 10 percent of the estimated maximum kilowatt demand, or the next larger standard size listed in table III, unless the next smaller 
Table III. Voltage Regulators-Standard Ratings 
Column (1) -Kilovolt-amperes Column (2) -Line amperes 
System Voltage 
2,400 4,160 4,800 7,200 12,000 
(1) (2) (1) (2) (1) (2) (1) (2) (1) (2) 
130  300  150  200  86.6  100  65  50  104  50  
150  348  187  250  130  150  130  100  156  75  
200  462  225  300  173  200  200  154  208  100  
250  577  250  333  260  300  250  192  250  120  
300  693  300  400  300  346  300  231  300  144  
375  866  375  500  375  433  375  289  325  180  
500  1,155  500  667  500  577  500  385  500  241  
600  1,386  600  800  600  693  600  462  600  289  
750  1,732  750  1,000  750  866  750  577  750  361  
1,000  481  
1,500  722  
2,000  962  
2,500  1,203  

13,800 23,000 34,500 46,000 69,000 
120 50 200 50.2 200 33.5 200 25.1 200 16.7 179 75 250 62.8 250 41.8 250 31.4 250 20.9 239 100 300 75.3 300 50.2 300 37.7 300 25.1 300 126 375 94.1 375 62.8 375 47.1 375 31.4 375 157 500 125.5 500 83.7 500 62.8 500 41.8 
50() 
209 600 150.6 600 100.4 600 75.3 600 50.2 600 251 750 188.3 750 125.5 750 94.1 750 62.8 750 313 1,000 251 1,000 167 1,000 126 1,000 83.7 
1,000 418 1,500 377 1,500 251 1,500 188 1,500 126 1,500 628 2,000 502 2,000 335 2,000 251 2,000 167 2,000 1,046 2,500 628 2,500 418 2,500 314 2,500 209 
6 

E. M. PART VICHAPTER 1 May 1953 
standard size will provide at least 90 percent of the required rating. For instance, therating of regulator for a camp, airfield, storage depot, or other facility having an estimatedmaximum demand of 2000 kilowatts and a distribution voltage of 13,800 volts would beselected as follows:Example: Ten percent of the estimated maximum demand (2000 kilowatts) is 200.Referring to table III it is noted that the next smaller size (179 kilovolt-amperes) is lessthan 90 percent of the required rating. The next larger standard rating (239 kilovoltamperes) would, therefore, be selected for the project.
h. Power company's meters. Provision should be made in the substation for powercompany's meters and metering transformers, in accordance with the power company'srecommendations. Care should be taken to insure that any wiring or conduits to be providedby the contractor in connection with the installation of power company's meters is includedin the contract drawings and specifications.
i. Protective provisions. Electrical protection to equipment and operators should beprovided by the use of lightning arresters and by an adequate grounding system. Protectionagainst intrusion should be provided by fencing. Gates should be equipped with padlocksto prevent the entrance of unauthorized persons.
(1) Lightning arreste1·s. Lightning arrester application is determined by the circuitvoltage rating and requires consideration of the minimum and maximum arrester voltagerating. Station-type arresters should be installed at all substations as this type of arresterhas a larger discharge capacity than the distribution or line types. Arresters should beselected so that the circuit voltage is within the \-oltage range given in table IV. If thecircuit voltage is below the minimum voltage rating of the arresters, the protection willnot be ail good as can be obtained. If the circuit voltage is above the maximum voltage ratingof the arresters, the arresters will likely be damaged. The maximum rating of arrestersgiven in table IV is expressed in terms of the maximum sustained voltage which may existfor any period on the system, including high voltages caused by transformer taps abovenormal voltage, voltage regulators, or light load operation. It is imperative that thearresters be so selected that the maximum permissible line to ground voltage will neverbe exceeded for any condition or period of operation. Arresters should be installed as closeto the equipment as wiring arrangements will permit. Figures 1 and 2 show typicallocations of lightning arresters. In some cases provision is made by the manufacturer formounting the arresters directly on the transformers and switchgear housings.
(2) Grounding system. The grounding system should consist of a lightning arresterground and a station ground. The lightning arrester grounding conductors should have acurrent capacity sufficient to insure continuity and continued effectiveness of the groundconnections under conditions of excess current ·caused by, or following, discharge of thearrester. Station ground should comprise at least six ground rods. These rods should beconnected to each other and to all equipment tanks or cases, metal structures, operatinglevers, neutral conductors, and metallic fence in such a manner that the path to groundwill not be broken by the manual or automatic operation of any equipment. Ground rodsshould be at least six feet apart and should be connected to each other about one foot belowthe finished grade. The lightning arrester and station grounds should be interconnected.No individual grounding conductor should have less conductance than No. 6 copper wire.
(3) Fence. The substation equipment should be entirely inclosed by a fence, preferably of the chain-link type with three strands of barbed wire at the top. Unless the fenceis of the removable-panel type, at least one double gate of sufficient width to permit theentrance of a truck should be provided. The height of the fence should be not less thansix feet. 
7 
E. M. PART VI CHAPTER 1 May 1953 
Table IV. Lightning Arresters 
Ungrounded neutral circuits Solidly grounded neutral circuits 
Nominal Arrester rating, Nominal Arrester rating, system maximum permissible system maximum permissible voltage line to ground voltage 1ine to ground class voltage class voltage (kilovolts) (kilovolts) (kilovolts) (kilovolts) 
2.4____________________ _ 3 4.16 3 4.16___________________ _ 6 4.8 6 4.8____________________ _ 
6 6.9 6 
6.9____________________ _ 9 11.5 9 11.5____________________ _ 
12 12.47 9 
13.8____________________ _ 15 13.8 12 18______________________ _ 20 18 15 23______________________ _ 25 23 20 
28.5____________________ _ 30 28.5 25 
34.5____________________ _ 37 34.5 30 46______________________ _ 50 46 40 57______________________ _ 60 57.5 50 69______________________ _ 73 69 60 
92______________________ _ 97 92 79 
115______________________ _ 121 115 97 
126.5____________________ _ 133 126.5 109 
138______________________ , 
145 138 121 
161______________________ _ 169 161 145 23Q______________________ _ 242 230 195 
\ 
1-12 SWITCHING STATION. Where the supply voltage is 13,800 volts or less, a switching station should be provided, unless a single distribution circuit will meet the requirements of the facility being served. Switching station should conform to the requirements of paragraph 1-11 covering substations, except for the omi~sion of transformers. As in the case of substations, provision should be made for the installation of power company's meters and metering transformers in accordance with the company's recommendations. Figures 6 and 7 show typical arrangement of switching stations for aerial and underground systems, respectively. 
1-13. EMERGENCY POWER SUPPLY. The necessity for emergency supply of electricity will normally be determined by the using agency. In prqjects wherein a temporary power interruption might result in a fire, explosion, extensive d~mage to equipment or loss of life, an emergency supply source should be provided. Permanent hospitals should be supplied by emergency engine-driven generators arranged to start automatically upon failure of the normal current supply and to stop upon its restoration. These generators should be sized and connected to carry the entire load of operating suites, exit lights, corridor lights at key points, stair lights, key lights in neurophychiatric sections and one passenger elevator where installed. Emergency circuits operating at 30 volts or less should be energized by a storage battery provided normally with a trickle charger. Emergency circuits operating at more than 30 volts should be energized by engine-driven generators, except in those instances wherein the power requirements are less than 500 watts and the proper battery maintenance is assured. The installation of 125-volt, 60-62 cell storage batteries will generally be avoided, due to their maintenance requirements and possible renewal or replacement costs at 5-7 year intervals. For the automatic operation of switchboard equipment or circuit breakers, 
8 

E. M. PART VI CHAPTER 1 May 1953 
alternating current with or without rectification units, should be utilized to the extent practicable and, where impracticable and a battery is considered mandatory, the voltage should not exceed 48 volts. 
a. 
. Fuel. In hospitals gas, if available, should be utilized as fuel for the engine; otherwise the fuel should be gasoline. At other installations, the fuel should be either gasoline or diesel, the determination being made on the basis of all pertinent factors involved. 

b. 
Speed. General-purpose emergency generating sets should have speeds not less than 1200 RPM. Special-purpose sets, or those rated in excess of 125 kw, 0.80 power factor, may be rated below 1200 RPM only if warranted by the anticipated conditions. In all cases ample consideration should be given to the anticipated total annual operating time, including test periods, prior to the selection of the lower speed units. In matters pertaining: to engine-driven generating units, attention is invited to SR 700-51-131. 


GENERATING PLANTS 
1-14 GENERAL. Where commercial electric service of the required capacity and reliability is not available or cannot economically be made available, generating plants should be provided. Generating plants for the normal supply of electricity will not be provided within the continental United States, however, without prior approval of the Office of the Chief of Engineers. 
1-15 TYPE. Unless steam-turbine generators can economically be operated in conjunction with a heating plant, the following types of generating equipment should be utilized : 
a. 
Units of less than 20 kilowatts. Generating plants comprising generators of less than 20 kilowatts should consist of gasoline engine-driven generators, unless some other type of fuel is more readily available and will result in a saving in the cost of electricity. 

b. 
Units of 20 to 50 kilowatts. Generating plants comprising generators of 20 to 50 kilowatts should consist of gasoline engine-driven or diesel engine-driven generators, as determined by the availability of engines and fuel and comparative cost of operation. 


c. Units larger than 50 kilowatts in plants of less than 7,500 kilowatts. Generating 
plants comprising generators having a capacity in excess of 50 kilowatts and having a total capacity of less than 7,500 kilowatts should be of the diesel engine-driven generator type. 
d. 
Plants of 7,500 to 15,000 kilowatts. Generating plants having a total capacity of 7,500 to 15,000 kilowatts should be of the diesel engine-driven or steam turbine-driven generator type, as determined by the availability of engines, comparative cost of operation, and availability of fuel. 

e. 
Plants exceeding 15,000 kilowatts. Generating plants having a total capacity in excess of 15,000 kilowatts should consist of steam turbine-driven generators with fuel selected in accordance with availability and minimum cost of operation. 


1-16 CAPACITY. With the exception of emergency plants and plants designed for intermittent service the capacity of the plant should be approximately equal to the estimated maximum demand with one of the largest generators out of service. The capacities of the individual generators should be selected to provide minimum standby capacity consistent with efficient operation, and adequate flexibility and such that the minimum demand (usually between midnight and 8 a.m.)_ will not be less than 30 percent of the capacity of the smallest generator. Consideration should also be given to the nominal demand (usually 11 a.m. to 3 p.m. and 7 p.m. to midnight). For instance, the generating plant for a project 
9 
E. M. PART VI CHAPTER 1 May 1953 
having an estimated maximum demand of 3,000 kilowatts, a nominal demand of 2,000 kilowatt and a minimum demand of 600 kilowatts would be selected as follows: 
Example: Either two 3,000-, three 1,500-, four 1,000, or five 750-kilowatt generators would carry the maximum demand with one generator out of service. The use of two 3,000kilowatt generators would result in excessive standby capacity and the operation of excessively large equipment during periods of nominal and minimum demand. The use of three 1,500-kilowatt generators would require the operation of excessively large equipment during period of nominal demand. Four 1,000-kilowatt generators would comply with all requirements and would be selected. The use of five 750-kilowatt generators would be rejected for lack of compliance with the requirements of paragraph 1-17. Available equipment approximating the required capacities should be utilized wherever practicable. Standby equipment should not be provided in emergency plants or plants designed for intermittent service. 
\ 
1-17 NUMBER OF GENERATORS. The number of generators in any plant should be the minimum required to provide adequate reliability and flexibility and should in no case exceed six. The number of different sized generators should be kept to a minimum and, in general, should not exceed two. Generating plants comprising only one generator should not be installed where electric service cannot frequently be cut off to permit inspection and maintenance of the equipment. Single generator plants should be limited to installations requiring intermittent service, such as floodlight banks which operate only at night or emergency plants which operate only upon failure of normal supply of electricity. 
1-18 PARALLEL OPERATION. All main generators in the plant should be so connected that any or all of them can furnish power to the main bus at the same time. 
1-19 VOLTAGE RATING. Voltage rating of generators should be determined by the size of the area to be served by the generating plant. In general, the generator voltage should be the lowest applicable standard voltage that can be carried over the distribution system without excessive voltage drop and without the use of excessively large conductors. Where generators with dual voltage rating of 2,400 delta and 4,160 wye are available for a project, the 4,160 volt wye connection should generally be selected for the system. Step-up transformers should be utilized only where their use will effect economy of operation and where required for proper operation of available equipment. :Joint NEMA-NELA preferred
I 
voltage ratings should be used unless these ratings conflict • with local conditions, such as interconnection with other systems or local procurement of equipment. Joint NEMA-NELA preferred voltage ratings are as follows: 
120 2,400 240 4,160 480 6,900 600 11,500 13,800 
1-20 FREQUENCY. ' Frequency should be 60 cycles wherev~r this frequency is applicable to the installation. 
1-21 BUILDING. With the exception of cooling towers and other outdoor accessories, all generator equipment should be installed in a building constiucted essentially of noninflammable materials. Adequate natural light and natural ventilation should be provided to 
10 

UbfWY 	us 64 
THr::'l c~ l'//i<":S, 11 anc1 12, CCN ;rri':'UTZ ChANGE 3 TO "Sll lll0-345-181, }L\Y ~30fj 7/(AFJI' 88-9 CHAP. l) 
El·i 1110-345-181 Chan::;e 3
AUG 2 6 1964 
15 J\m 64 
facilitate maintenance and efficiency of operation. In warm climates engine-generators with air-cooled radiators should be so installed that the heated air will discharge outside of the building. 
1-22 FOUNDATIONS. Concrete foundations should be provided for each piece of equipment having a weight in excess of the capacity of the floor of the building. The size and depth of the foundations should be determined from data furnished by the equipment manufacturer. Where manufacturer's data are not available an opening should be left in the floor until the weight and dimensions can be obtained from the equipment to be installed. A %-inch space should be provided between the engine-generator foundations and the floor of the building in order to reduce the effects of vibration. This space should be filled with vibration insulation material. 
1-23. FUEL STORAGE. In addition to the day tank usually furnished with gasoline and diesel engine-driven generators, an underground storage tank should be provided for all plants of these types, with the exception of small portable plants which can conveniently be furnished with fuel often enough to preclude the necessity for a storage tank. The storage tank should be of sufficient capacity to operate the plant for at least 2 weeks during the months of largest average demand. This capacity should be increased as required when deliveries of fuel at 10-day intervals cannot be relied upon. Actual fuel consumption of the engines and estimated number of hours of operation should be used in determining the capacity of storage tank whenever this information is available. When actual fuel consumption is not available an average of 4 kilowatt-hours per gallon of gasoline and 10 kilowatt-hours per gallon of diesel oil will be sufficiently accurate for this purpose. 
l-23A. H~AT R~COV~lY. Any installation which produces prime power from diesel encines, other internal combclstion encines, or gas turbines 1 ·.,rill cive full consideration to t · e use of Haste heat boilers to reclaim all possi~'le heat econorr.ically consistent with the total heating and/or air conditioning requirement of the installation. Diesel and other internal combustion enEines will be e~uipped with jacket water heat recovery equipment to reclaim heat to tLe maximum extent that it is economically feasible to use such reclaimed heat. All possible heat economically
obtainable from waste heat boilers will be used before additional 
heatinc :plants are constr,.cted on any installation. 1t/here diesel 
' 	eneines or other type en.:;ines or tu~''bines are used frecmently 
for power production, an economic study will be made to determine 
the feasibility of using heat from waste heat boilers and engine 
jacket water heat recovery equipment. • 

11 


E. M. PART VI-CHAPTER 1-,--May 1953 
APPROXIMATE HEIGHT OF 
_FOUR COLUMN STEEL STRUCTURE 

KILOVOLTS  HEIGHT,  
"  
23  GROUP OPERATED, HORN GAP  
34.5..  23 23  DISCONNECTING SWITCHES  

1" LIGHTNING RODS---
13.8 KV FEEDERS 
FOUR COLUMN HEEL 
STRUCTURE 
TWO COLUMN STEEL 
PRIMARY FUSES 
LIGHTNING ARRESTERS 
CONCRETE BASES 
ELEVATION 
.. -------r-----
---------o-------0----------<>
----<>------------·-o-----~----......--o----
I 
I 
INCOMING 
44 KV 
lllo"XB'·O" 
__ ~GROUND ROOS 
I
-l \
13.8 KV 
I 
FEEDERS 
I 
PRIMARY FUSE1 
INCOMING 
PLAN 
FIG. 1 
TYPICAL 750 KVA .u/13.8 KV CONVENTIONAL SUBSTATION FOR AERIAL SYSTEMS, 
UTILIZING SINGLE-PHASE TRANSFORMERS 

12 

E. M. PART VI
CHAPTER 1 May 1953 
facilitate maintenance and efficiency of operation. In warm climates engine-generators with
air-cooled radiators should be so installed that the heated air will discharge outside ofthe building. 
1-22 FOUNDATIONS. Concrete foundations should be provided for each piece of equipment having a weight in excess of the capacity of the floor of the building. The size anddepth of the foundations should be determined from data furnished by the equipmentmanufact~rer. Where manufacturer's data are not available an opening should be leftin the floor until the weight and dimensions can be obtained from the equipment to beinstalled. A %-inch space should be provided between the engine-generator foundationsand the floor of the building in order to reduce the effects of vibration. This space shouldbe filled with vibration insulation material. 
1-23. FUEL STORAGE. In addition to the day tank usually furnished with gasolineand diesel engine-driven generators, an underground storage tank should be provided for
all plants of these types, with the exception of small portable plants which can convenientlybe furnished with fuel often enough to preclude the necessity for a storage tank. Thestorage tank should be of sufficient capacity to operate the plant for at least 2 weeks duringthe months of largest average demand. This capacity should be increased as requiredwhen deliveries of fuel at 10-day intervals cannot be relied upon. Actual fuel consumptionof the engines and estimated number of hours of operation should be used in determiningthe capacity of storage tank whenever this information is available. When actual fuelconsumption is not available an average of 4 kilowatt-hours per gallon of gasoline and10 kilowatt-hours per gallon of diesel oil will be sufficiently accurate for this purpose. 
11 
E. M. PART VI-CHAPTER 1-May 1953 
APPROXIMATE·HEIGtCT OF 
FOUR COI..UWI STE&L STRUCTURE 
KILOVOLTS HEIGHT, FEET 

GROUP OPEilATED, HORN GAP DISCO...ECTMtG SWITCHESJ4.S
.." "" " 
23 \\ 
ELEVATION 
----r-
1
I 

INCOMING 
""XI'-0" 
__~GROUND RODS 
-lI 
lJ.I ICV I 
FEEDERS 
I 
I'RD&AIIY FUSES 
FENCE 
IHCOiliMG 
FIG. 1 
TYPICAL 7.50 KVA 44113.8 KV CONVENTIONAL SUBSTATION FOR AERIAL SYSTEMS. 
UTILIZING SINGLE-PHASE TRANSFORMERS 
12 
i 
\I
I 
E. M. PART VI-CHAPTER 1-May 1953 
GROUP OPERATED. HORN GAP DISCONNECTING SWIT;:::C"="-----;--------------, 
APPROXIMATE HEIGHT OF 
SIX COLUMN STEEL STRUCTURE 
ltiLCI'Y.LLTS 
HEIGHT FEET 
23 " " 
]4.5 .." 
.. 
" 
PRIMARY FUSf:S 
LIGHTNING ARRESTERS 
ELEVATION 
I J 
"-, ' ~ -~ INCOMING ' 
",. !';' I
" r----' ------l'f___ -~······•" 
GROUND RODS 
: ~ 'l 
r=="t--t
~RD~ /\ /\ / 
~~ ~ ~: 
...... ,
I ~ v ~ 
r--=-j [.e. ,.-~ 
I
~ I I,-. t--~ ~~ 
@..:: ~ ~ crt.. I
' I &i L"'-'-'-~'i

~~---,, I I""' ~
" 
'-== I' ~~ I 
PRIMARY FUSES
TR...M!f"01U4a 
~ li
P:: '~~ ', : ~ 
J L:----
~ 1--Sf \! ~ 
13.1 KV FEEDERS 
~/'{!~~..£1 
sri
t\lw ~ H~~~ ~ -t______ 
-.--c-I ~ 
.NI. .
I 
Pc II ~ -----------~--~ 
~~'WI
lr~ ~ t w 
.,. ~ I La ,..-1!/ I 
~ I"' 
~ ~ I I@ 
[o~ ~-1 f: ""' I 
'-,_ ·'"' I ,... \ '"'l
...__ ........ 

'------TUIIM'O....I..Il 
~ 
SWITCHGEAR 
---~ ~ ~~~/ (~~ ~II~~~·-
11. 
~ j, ~ A'!
~L~v ~v--v--'\t::--1 
I r
I \ lI : I 
F£MCE~ ~ 
./ ~ 
'"'""'""'
.... 
PLAN 
FIG. 2 
TYPICAL 2,tll0 kVA • -"113.8 KV CC»>VENTlOW.. SUBSTATION FOR AERIAL SYSTEMS. 
UTILIZING THREE~ TRAHSFORMERS 

13 
E. M. PART VI-CHAPTER 1-Mal_1953 
~...TEHE.,.,-01' TWO <=CIL~ lTEfL STIIlJCTl.u 
.. 

I
I 
LI _____ _
I
I
I
I
I
I

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I
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t-------II 
1
I 
r---•w•CMIOUIID.., 
I
I 
I I
~------,-1-------------------rl---•"•..... --.... 
I I 
14
""''
1'"lf'ICAI.. ...KYA-W111 EV !.NT ..TATDt R11: AH1M. IT'I11!IIIC 
E. M. PART VI-CHAPTER 1-May i953 
API"ItOXlMATE HEJCHT Of" TWO COLU.. STEEl. STRUCTURES 
~--~r-------~~------~----
" 
" n 
n 
IMCOMIMG I 
.un I 

I 
i 
I 
I 

!-.----
1 
I 
I 
I 
I 
I 
I 
I 
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I 
I 
I 
I 
I 
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I 
-----1 
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I ( 
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r---
1 
I 
I 

IMCOIIIMG I 
.UICV 
I 
j 
! 
~ f---IU ltV I'EED£11$ 15 ·~:::..-=..=s 
FIG.. .C 
TYPICAL .... IVA Wll.IICV l.MT SUBSTATklM FOR lH)ERGROlHJ SY$UIIS 

E. M. PART VI-CHAPTER 1-May 1953 
SWITCH "A" CAN NOT BE OPENED UNLESS CONNECTION DIAGRAM • "B" IS CLOSED. 
• "B" CAN NOT BE OPENED UNLESS
• 
"A" IS CLOSED. 
D

VOLTAGESWITCHGEAR REGULATOR 
11 
1 11 1!..----~--ALTERNATE 
II ''-~=-==-~::::'/ 1)i UNDERGROUND 

\\ '-'-::::::::-= =---=--=---=--= =--=---=::../I 
ELEVATION A-A 
VOLTAGE 

CONCRETE BAS: 
REGULATOR 
__lr t 

~\ 
,, '---t--+-+--' 
\\ 
FEEDER  FEEDER  METERING  MAIN C/B  
C/B  C/B  REGULATOR  CUBICLE  NO. 1  
DISCONNECT  
CUBICLE  

PLAN 
FIG. 5 
TYPICAL VOLTAGE REGULATOR INSTALLATION 

16 


E. M. PART VI-CHAPTER 1-May 1953 
SWITCHGEAR 
FEEDER FEEDER FEEDER FEEDER FEEDER MAIN CB If METERS/'
CB ,f CB ,f CB I CB If CB I 
3 COLUMN STEEL STRUCTURE 181 HIGH 
ELEVATION 
GROUND BUS 
SWITCHGEAR 
~CONCRETE 
BASE 
PLAN 
FENCE--/
FIG. 6 
TYPICAL SWITCHING STATION FOR AERIAL SYSTEMS 

17 


E. M. PART VI-CHAPTER 1-May 1953 
r---,---,-'--.-r-r--. -, 
I I I 
P>)li
I I I /'/ .
I AI I I w I I /'
,A. ,A.
~ ~ 1' 1' ~ "" ~ 1' 5-·.·> 
' rl, r-, r-; rl, r--r r-; '/
'""' 
LwJ LTJ Lr.J LIJ LrJ L,--1·' y y 'V 'V v v 
"i '[
{., f t { r+ 
r~-_l
' ' 

TEST FEEDERS METERS INCOMING RACK SUPPLY 
ELEVATION 
FENCE 
SWITCHGEAR 
(_CONCRETE BASE) 
PLAN 
FIG. 7 
TYPICAL SWITCHING STATION FOR UNDERGROUND SYSTEMS 

18 
E•. M. PART VI 
CHAPTER 1 May 1953 
AERIAL ELECTRICAL DISTRIBUTION AND STREET LIGHTING SYSTEMS 
1-24 GENERAL. Aerial systems should be employed in all areas except within 300 feet of towers containing high frequency equipment and where safety precautions, such as flight hazard and the use of material handling equipment require the use of underground 
cable. No exceptions will be made to this requirement without prior approval by the Office of the Chief of Engineers. 
1-25 POLE LINES. Pole lines should be installed along streets or roads, wherever practicable, in order to avoid the use of separate poles for street lights. Figure 8 shows a typical layout of pole lines for an aerial electrical distribution and street lighting system. For uniformity, symbols shown on figure 9 should be used to indicate pole line construction on drawings. Poles, cross arms, loading, guying, clearances, spans, sags, and tensions should comply with the requirements of National Bureau of Standards National Electrical Safety Code (Handbook H30 or latest revision thereof) for grade"B" construction. National Bureau of Standards Handbook H43 contains a discussion of part 2 of the National Electrical Safety Code which may be helpful in connection with the design of the aerial electrical distribution and street lighting system. In connection with the selection of pole lengths, allowance should be made for the installation of telephone lines on all distribution poles. These lines are usually installed by the Signal Corps, Air Force or the local telephone company, but the designer of the distribution system is responsible for the additional space and strength requirements. Pole lengths specified should include the section below ground line. Table V indicates the average setting depth of poles in normal firm ground. Class of pole should be selected on the basis of having the minimum breaking strength at the ground line listed in table VI. For grade "B" construction, the poles should have four times the strength required for supporting the actual vertical and transverse loading, except that 
when the poles are guyed, the guy should support the entire load in the direction in which it acts, the pole simply acting as a strut. 
Table V. Pole Setting Depth 
Straight lines Curves, comers and points of extra strain
Pole length, over-all, reet  
Feet  Inches  Feet  Inches  
30-------------------"-35_____________________ _ 40_____________________ _ 45_____________________ _ 50_____________________ _ 55_____________________ _ 6Q_____________________ _ 70_____________________ _  5 6 6 6 7 7 8 9  6 0 0 6 0 6 0 0  5 6 6 7 7 8 8 9  6 0 '6 0 6 0 6 6  

Table VI. Poles 
Class or pole Minimum breaking Class or pole Minimum breakingstrength (pounds) strength (pounds) 
1-~-----------------.
2__________________ _ 4,500 5------------------1,900
3,700 6_________________ _ 1,5003__________________ _ 3,000 7_________________ _ 1,200 
4~------------------2,400 
19 

E. M. PART VI CHAPTER 1 May 1953 
1-26 PRIMARY CIRCUITS. The number of primary circuits should be established on the basis that each circuit will carry the kilovolt-ampere load listed in table VII for the distance indicated, without exceeding a 2 percent voltage drop. The kilovolt-ampere load should be determined by adding the kilovolt-ampere rating of all transformers to be connected to the circuit and applying a suitable diversity factor. A diversity factor of 60 percent will be sufficiently accurate for most feeder calculations. This diversity factor should be increased to 100 percent, however, where the circuit will feed a load wherein all of the distribution transformers will be operating at full load at the same time. The use of conductors larger than No. 0-AWG copper or equivalent should be avoided wherever practicable, as the larger conductors are difficult for small maintenance crews to handle. Not more than two primary circuits should be carried on one pole line. Where primary circuits are suitably located, disconnecting switches should be provided to permit the load from one circuit to be transferred to another in case of emergency. A loop circuit or two radial circuits should be provided at all hospital transformer banks, to insure a continuous supply of electricity during inspection and repair operations, unless the cost involved is inconsistent with the cost of the project under design. All primary circuits should be installed on cross arms. F:'igures 10 through 13 show typical arrangements of primary circuits. 
Table VII. Three-Phase Primary Circuit Loading 
[Kilowatt capacity of wires and maximum distance in feet to load center for 2 percent voltage drop, aerial systems] 
Wire size AWGorMCM 
Copper  I  Aluminum and ACSR  Kilowatts  100 percent pf distance  Kilowatts  80 r,rcent pf istance  
2,400-volt  
8________________ 6________________ 4________________ 2________________ 1________________ 1/0______________ 2j0______________ 3/0______________ 4/0______________ 250______________ 300______________ 350______________ 400______________ 500______________  6 4 2 1/0 2/0 3/0 4/0 266.8 336.4 397.5 477 556.5 636 795  295 407 541 733 845 985 1,140 1,320 1,530 1,700 1,910 2,110 2,300 2,610  670 720 860 1,010 1,090 1,195 1,300 1,430 1,540 1,610 1,630 1,760 1,920 2,100  236 326 433 586 676 788 912 1,058 1,224 1,360 1,530 1,690 1,840 2,090  670 720 780 805 805 795 785 770 735 710 670 646 630 550  
4,160-volt  
8________________ 6________________ 4________________ 2________________ 1________________  6 4 2 1/0 2/0  511 705 936 1,267 1,460  1,160 1,250 1,480 1,750 1,880  409 564 749 1,011 1,168  1,160 1,250 l,330 1,400 1,400  
1/0-------------2/0______________ 3/0______________ 4/0______________ 250______________ 300______________ 350______________ 400______________ 500______________  3/0 4/0 266.8 336.4 397.5 477 556.5 636 795  1,710 1,970 2,290 2,650 2,950 3,3JO 3,650 4,000 4,520  2,070 2,250 2,480 2,650 2,790 2,830 3,050 3,340 3,650  1,369 1,572 1,830 2,120 2,360 2,640 2,920 3,200 3,610  1,380 1,360 1,330 1,270 1,230 1,160 1,120 1,090 1,040  

20 

E. M. PART VI CHAPTER 1 May 1953 
Wire size 
AWGorMCM 

I 
100 l"'rcent 80 Ji.rcent Kilowatts pf d1stance Kilowatts pf istance
Aluminum
Copper and ACSR 
4,800-volt 
8________________ 
6 590 1,340 471 1,340
6________________ 
4 814 1,440 650 1,440
4________________ 
2 1,080 1, 710 864 1,550
2________________ 
1/0 1,460 2,030 1,170 1,610
1________________ 
2/0 1,690 2,170 1,300 1,610
1/0______________ 
3/0 1,970 2,390 1,570 1,590
2/0______________ 
4/0 2,280 2,590 1,820 1,570
3/0______________ 
266.8 2,640 2,850 2,110 . 1,530
4/0______________ 
336.4 3,060 3,080 2,450 1,470
250______________ 
397.5 3,400 3,200 2,720 1,420
300______________ 
477 3,820 3,260 3,300 1,340
350______________ 
556.5 4,220 3,520 3,380 1,290
400______________ 
636 4,600 3,840 3,680 1,260
500______________ 
795 5,220 4,210 4,180 1,200 
7,200-volt 
8________________ 
6 884 2,000 706 2,000
6________________ 
4 1,220 2,160 975 2,160
4________________ 
2 1,620 2,570 1,300 2,330
2________________ 
1/0 2,190 3,040 1,750 2,410
! ________________ 
2/0 2,530 3,260 2,020 2,410
1/0______________ 
3/0 2,950 3,590 2,360 2,390
2/0______________ 
4/0 3,410 3,900 2,730 2,360
3f0______________ 
266.8 3,960 4,280 3,170 2,300
4/0______________ 
336.4 4,580 4,620 3,660 2,200
250______________ 
397.5 5,110 4,830 4,100 2,130
300______________ 
477 5,730 4,900 4,580 2,000
350______________ 
556.5 6,320 5,280 5,050 1,940
400______________ 
636 6,900 5,780 5,520 1,890
500______________ 
795 7,830 6,320 6,260 1,800 
12, 000-volt 
6 1,470 3,340 1,175 3,340
8---------------
6----------------4 2,040 3,600 1,630 3,600 
4----------------2 2,700 4,280 2,160 3,900 
2----------------1/0 3,650 5,060 2,920 4,020 1----------------2/0 4,220 5,430 3,380 4,020
;o______________
1 3/0 4,710 5,980 3,920 3,980 
2;o______________ 
4/0 5,690 6,500 4,550 3,930 
3;o______________ 
266.8 6,600 7,150 5,280 3,840 

4;o______________ 
336.4 7,650 7,690 6,120 3,680 
250______________ 
397.5 8,510 8,050 6,800 3,550 

3oo______________ 
477 9,550 8,160 7,640 3,350
50______________

3 556.5 10,550 8,800 8,440 3,230 400 636 11,500 9,640 9,210 3,150
oo --------------______________

5 795 13,060 10,500 10,400 2,990 
21 


E. M. PART VI 
CHAPTER 1 
May 1953 

Wire sUe 
AWG orMCM 

100/uerceo~ soc~ Kilowa~ta pf it!tance Kilowa~ta pf it!tance
I 
AluminumCopper aod ACSR 
13,800-volt 
8________________ 6 1,690 3,840 1,350 3,8406________________ 4 2,340 4,130 1,870 4,1304________________ 2 3,100 4,930 2,480 4,4702________________ 1/0 4,200 5,820 3,360 4,6301________________ 2/0 4,850 6,250 3,880 4,630lfO______________ 
3/0 5,650 6,880 4,520 4,580 2/0--------------4/0 6,540 7,460 5,220 4,510
3/0______________ 
266.8 7,600 8,220 6,080 4,410
4/0______________ 
336.4 8,780 8,850 7,020 4,230
250______________ 
397.5 9,790 9,260 7,820 4,080
300______________ 
477 10,980 9,400 8,780 3,850 .350______ --------556.5 12,100 10,100 9,670 3,720
400______________ 
636 13,200 11,100 10,550 3,620
500______________ 
795 15,000 12' 100 12,000 3,440 
Notes. I. All voltages are line to line. 
2. 	
Wire capacities are for bare or weatherproof wires. 

3. 	
Wires run overhead with effective spacing of 18 inches. 

4. 	
To compute the maximum distance to a load center with 2 percent voltage drop for connected !oads not listed above: &a Select ftt.m the table the desired wire size which will carry the load at the applicable voltage rating. 

b. 	
Multiply the "kilowatts" given in the table by the "distance" given in the table, for the selected wire size. 

c. 	
Divide this product by the actllal load in kilowatts. 

d. 	
If the computed distance is not adequate, select a larger wire size and repeat the calculation. 


1-27 SECONDARY CIRCUITS. Secondary circuits should be installed on the poles carrying primary circuits where these poles are suitably located for the purpose. Secondary conductors should be supported below the primary lines on secondary racks, clevises, or wire holders, as applicable. Figures 14, 15, 16, 17, 18 and 19 show typical arrangements of secondary circuits. Conductors should be triple-braid, weatherproof-covered. The following maximum wire loading is recommended, based on a 55° C. temperature rise, provided the voltage drop given in paragraph 1-28 is not exceeded. 
AWG size 
AmperesCopper Aluminum and ACSR 
8 ________________________________ 6 _________________________________ _ 
85 6--------------------------------4_________________________________ _ 105 
4____ ---------------------------2-------------------C-------------
145 2--------------------------------1/0_______________________________ _ 200 
o________________________________ 2f0_______________________________ _ 
280
2f0______________________________ 4f0_______________________________ _ 
315 4/0_ __ __ __ ____ _____ ___ ____ ___ ____ 336.4 MCM______________________ _ 
425 
250 MCM________________________ 397.5 MCM_______________________ _ 475 
300 MCM________________________ 477 MCM_______________________ _ 525 
400 MCM________________________ 636 MCM_______________________ _ 650 
500 MCM________________________ 795 MCM_______________________ _ 750 
22 

EM 1110-.345-181Change 124 Jun 57 1-28 VOLTAGE DROP. Voltage drop should not exceed 2 percent on the primary andsecondary circuits, respectively. 
1-29 TRANSFORMERS. Transformers should be of the self-cooled type, with ratingselected from table I. Where the required size is not listed in the table, the next larger sizeshould be installed unless the next smaller size will provide at least 90 percent of the requiredrating. Transformers or transformer banks having a capacity in excess of 75 kilovolt
amperes should be installed on two-pole platforms or on concrete mats. Smaller transformersshould be pole-mounted. Figures 21, 22, 23, and 24 show typical transformer installations.Wye-wye connected transformers should not be utilized where the primary neutral is notavailable or within 500 feet of radio stations or navigational aid facilities. All transformersinstalled outdoors or in fireproof transformer vaults should be of the oil-insulated, selfcooled type. Transformers installed within buildings in which fireproof vaults have notbeen provided should be of the non-inflammable liquid-or air-cooled type unless theatmosphere in which the transformer is to be installed is moist or dusty. In moist or dustyareas, transformers installed within buildings in which fireproof vaults have not beenprovided should be of the nonflammable-liquid-cooled type. 
Transformer capacitiesshould be selected so that all transformers will be operating as nearly as practicable to theallowable temperature limits during periods of maximum demand. In general, the capacityof transformers should be equal to approximately 60 percent of the connected load, exclusiveof family quarters. The transformer capacity for each installation, however, will requirespecial study and will vary from a demand factor of 30 percent for large hospital buildingsto a demand factor of 100 percent for isolated power installations. Demand factors forfamily quarters with or without electric ranges and water heaters are approximately asfollows: 
Number of quarters Demand factor Number of quarters Demand factor Number of quarters Demand factorper cent per cent 
per cent
19 ______________ _ 	37 ______________ _80.0
21________________----------------_ 	18.0 13.2
60.0 20 ______________ _ 	38 ______________ _
3 ________________ _ 21 __ , ___________ _ 17.5 	13.0
50.0 	39 ______________ _
4 _______________ _ 22______________ _ 17.1 	12.8
45.0 	16.6 40 ______________ _
5________________ _ 23 ______________ _ 	12.6
40.0 	41 ______________ _
6________________ _ 24 ______________ _ 16.1 	12.4
35.0 	15.8 42 ______________ _ 12.2
7________________ _ 25 ______________ _ 	43 ______________ _
32.0 15.6 	12.0
8________________ _ 	26 ______________ _
29.0 	15.4 44 ______________ _
9________________ _ 	11.8
27.0 27 ______________ _ 15.2 45 ______________ _
10________________ _ 	11.6
25.0 28 ______________ _ 	46 ______________ _
}} ________________ _ 	15.0 11.4
24_0 29 ______________ _ 14_8 47 ______________ _ 11.2
12________________ _ 	30______________ _
23.0 	14.6 48 ______________ _ 11.0
13________________ _ 31 ______________ _ 	49 ______________ _
22.0
14 ________________ _ 	14.4 10.8
21.0 32______________ _ 	50 ______________ _
15________________ _ 33 ______________ _ 14.2 	10.6
20.0 	14.0 51 ______________ _ 10.4
19.4 34______________ _ 	52 ______________ _
13.8 	10.2
~~~~~~~~~ ~ ~ ~ ~~~ ~ ~~~/ 18.7 35______________ _ 13.6 53 ______________ _
18________________ _ 18.3 I a6 ______________ _ 13.4 54 and ovcr_ _____ _ 10.1
10.0 
I 
Note. 	Where electricity is used for Stlace heating the total connected heating-load should he addM to the demands obtained bythe use of this table. 
23 
E. M. PART VI CHAPTER 1 May 1953 
1-30 GUYING. Particular care should be taken to insure that all points of strain in the pole lines are adequately guyed. Improperly or inadequately guyed lines will soon begin to sag, creating an unsightly installation and resulting in increased cost of maintenance. Insulators ~hould be so positioned in the guy wire that, in the event the guy wire is broken the uninsulated upper portion of the guy wire cannot swing to any point less than 8 feet above the ground. Figure 20 shows typical methods of guying pole lines. The number and location of all guys should be shown on the construction drawings. 
1-31 SERIES STREET LIGHTING SYSTEMS. Series systems may be either 6.6 or 20 amperes and should employ complete metallic loops. Series street lighting wires should normally be placed on the outside pins of the cross arms or, when poles are installed for series street lighting purposes only, the wire may be installed on pole-top pin insulators and the cross arms may be omitted. Single circuits should be limited, if possible, to 30 kilowatts or less, using pole-type transformers. Where it is necessary to use constant current transformers larger than 30 kilowatts, they should be of the indoor type and should be installed in suitable fireproof vaults. Table VIII lists the number of group replacement straight series lamps with film cutout which can be connected to each standard size regulator. The capacity of regulator for mixed loads comprising a number of 2,500 lumen lamps and a number of 4,000 lumen lamps may be determined by adding the size of regulators required for the 2,500 and 4,000 lumen lamps, respectively. Street lighting regulators should always be as fully loaded as practicable since the primary power factor drops sharply under light load conditions. Supplementary multiple lights may be used on 6.6 ampere systems, in which case insulating transformers with multiple secondary windings should be employed. Control should be by means of a primary switch operated by a time switch. Figure 25 shows a typical installation of street lighting regulator and control. 
Table VIII. Street Lighting Transformers 
Number of straight aeries lamps 6. 6 ampere Transformer ratingKW 2,500 lumen 4,000 lumen 
31 22
5------------------------------
7.5____________________________ _ 
47 33 
10 ______________________________ _ 
62 44 
15______________________________ _ 
94 66 
20______________________________ _ 125 88 
25______________________________ _ 156 llO 
30 ______________________________ _ 
188 132 
1-32 MULTIPLE STREET LIGHTING SYSTEMS. Multiple systems utilizing extensions to the primary or secondary electrical distribution systems should be employed where a small number of lamps are to be installed within a reasonably small area. Control should be by means of weatherproof safety switches located approximately 6 feet above the ground on a pole or other convenient place. 
1-33 STREET LIGHTING UNITS. Street lighting units should consist of bowl refractor luminaires in administration, recreation and hospital areas and 20-inch radial wave reflectors 
24 

E. M. PART VI CHAPTER 1 May 1953 
in quarters, barracks, industrial, warehouse, utility and storage areas. Radial wave reflectors should also be installed along roads outside of the building areas when street lighting is considered necessary. Lighting intensities should be based on the installation of 4,000 lumen series lamps or 200-watt multiple lamps spaced 150 to 200 feet apart in administration, recreation and hospital areas, and 2,500-lumen series lamps or 150-watt multiple lamps spaced 150 to 200 feet apart in quarters, barracks, industrial, warehouse, utility and storage areas. These spacings should be measured along the center line of streets designed for two or three lanes of traffic and along each sjde of streets designed for more than three lanes of traffic and along streets having parkways in the center. One street lighting unit should be installed at each intersection designed for two or three lanes of traffic and two street lighting units at each intersection designed for more than three lanes of traffic and streets having parkways along the center. 
25 

FOR SYMBOL$ -SEE FIG. 9 
FIG.& 
TYPICAL LAYOUT 
A,U,IAL ELECTRICA\.. D\5TibBUTION. !.Y~Tf."" 
E. M. PART VI-CHAPTER 1-May 1953 
0 	35-5 35-5-6M 
0---i 
35-5-2500 
o-n 
A 	1s 
6. 50 
¢15 

__r-___ 
~ 
• LA 
312 __11_1!..._ ___ 3112 
--~*-.1.___ 
POLE -LENGTH AND CLASS INDICATED. 
POLE WITH DOWN GUY AND ANCHOR -LENGTH AND CLASS OF POLE AND 
STRENGTH OF GUY IN POUNDS AS INDICATED. 
POLE WITH STREET LIGHT -LENGTH AND CLASS OF POLE AND SIZE OF 

LAMP IN LUMENS OR WATTS AS INDICATED. 
SINGLE-PHASE TRANSFORMER -RATING IN KVA AS INDICATED. 
THREE-PHASE TRANSFORMER -RATING IN KVA AS INDICATED. 
STREET LIGHTING REGULATOR -RATING IN KW AS INDICATED. 
SECTIONALIZING SWITCH MOUNTED ON CROSSARM-NORMALLY OPEN. 
SECTIONALIZING SWITCH MOUNTED ON CROSSARM-NORMALLY CLOSED. 
POLE TOP SWITCH. 
LIGHTNING ARRESTER IN EACH PHASE WIRE . 

PRIMARY LINE -NUMBER AND SIZE OF WIRES AS INDICATED. 
SERIES STREET LIGHTING CIRCUIT -SINGLE CONDUCTOR -OF SIZE INDICATED. 
THREE-PHASE SECONDARY LINE -NUMBER AND SIZE OF WIRES AS INDICATED. 
SiNCOLf.-PHAJ>E. ~E.CONOA~Y LINE-NU...8E.It AND SiZE. OF WI~ES AS INDICATED. 

CONOUC:.iOR DEADE.ND, 
FIG. 9 STANDARD SYMBOLS AERIAL ELECTRICAL DISTRIBUTION CONSTRUCTION 
27 

E. M. PART VI-CHAPTER 1-May 1953 
CLIMBING 
SPACE 
~ 
FIG. 10 
L -CORNER -(4 WIRE) 

28 
E. M. PART VI-CHAPTER 1-May 1953 
r r -r 
r 
r
~  ""'I""  )  
0  
I  IR F  .1 I  
{C  {I  0  ..c.,, .  (lp)  0  (! PJ  J  
~=~  
CLIMBING  0  
SPACE  
)  ""'  )  
r  f"'  I  
)  ~  )  
I  p  I  
'-- 

FIG. 11 
X-CORNER (4 WIRE) 
29 
E. M. PART VI-CHAPTER 1-May 1953 
CLIMBING 
SPACE 

DOWN GUY 
0 
ARM GUY AS REQUIRED 
l 
PLAN 
L---DOWN GUY 
ELEVATION 
FIG. 12 
TYPICAL "T" CORNER 
30 
E. M. PART VI-CHAPTER 1-May 1953 
GUY 
ANGLE COND. 
ANGLE 
Ic.;i]
6 24-60° 6 1 
2 12-60° 2 1/0 s-60° 110 I 410 4-60° .C/0 ' 
.__________ -_l --_j
NOTE: --
FOR :.ONGLES GREATER THAN 60° 
USE CORNER TYPE CONSTRUCTION. 

FIG. 13 DOUBLE ARM 
.31 


E. M. PART VI-CHAPTER 1-May 1953 
I 
~ 
LINE CONDUCTOR, ON OUTtiDE OF INSULATOR ON STRAIGHT RUNS 
PLAN 
LINE CONDUCTOR, ON OUTSIDE OF INSULATOR ON STRAIGHT RUNS 
ELEVATION 
FIG. 14 
STRAIGHT-LINE INSTALLATION 
32 
E. M. PART VI-CHAPTER 1-May 1953 
THESE TWO ANGLES TO BE EQUAL 
LINE CONDUCTOR ON INSIDE OF INSULA TOR 
GUY AS REQUIRED 
FIG. 15 
ANGLE INSTALLATION 

33 
E. M. PART VI-CHAPTER 1-May 1953 
GUY AS REQUIRED 
/ 
PLAN 
ELEVATION 
FIG. 16 
CORNER INSTALLATION 

34 
E. M. PART VI-CHAPTER 1-MaJ1951 
PLAN 
ELEVATION 
FIG. 17 CROSS 
35 
B. M. PART VI-CHAPTER 1-May 1953 
GUY AS REQUIRED 
PLAN 
FRONT ELEVATION 
SIDE ELEVATION 
FIG. 18 
TEE TAP 

36 
E. M. PART VI-CHAPTER 1-May 1953 
SECONDARY LINE CONDUCTORS 
SERVICE DROPS NUMBER AS REQUIRED 
PLAN 
FIG. 19 
TYPICAL SERVICE CONNECTIONS 

37 
E. M. PART VI-CHAPTER 1-MaJ1953 
CURVED WASHER THIMBLEYE BOLT ./"'-
STRAIN INSULATOR 
61-0"MIN. 
8'-0"MIN. 
LIFT PLATE 
2 BASE OR 3 BOLT CLAMP 
EXPANSION  
ANCHOR  
DOWN GUY  
NOTE:  - 
"A"-STANDARD SIDE GUY.  
"B" -USE GUY STUB WHERE  
METHOD  "•'" DOES NOT  
GIVE SUFFICIENT  
CLEARANCE.  
FIG. 20  
TYPICAL POLE GUYING  

38 

INSULATOR 
PLACED IN 
CENTER OF SPAN 

NO INSULA TOR 
I 
GUY PROTECTOR 
HEAD GUY 
STORM GUY 
E. M. PART VI-CHAPTER 1-May 1953 
,----STANDARD SIDE GROOVE \ 
USE 	ONLY 3d POSITIONS ON FUSE ARM. 
18~" WHERE 3cl INSTALL GROUND POSITION IS TO BE MOULDING UNDER USED. 4" OTHERWISE. ARM TOWARD FACE OF ARM. 
NOTE: TRANS. MAY BE 
MOUNTED ON CROSSARM 
IF DESIRED. 

FINISHED 
CRADE 

/ 
POLE/ 
~STAPLES
TO BE TWO FT. APART 
COIL TYPE GROUND 
GROUND LEAD 
TAP CONNECTOR 
TAP CONNECTORS IF NECESSARY 
LOOP GROUND LEAD OUT TO SECONDARY NEUTRALGROUND RODS GROUND CONNECTIONS 
POLE 
TY_PICAL CONNECTION FOR TWO GROUND RODS 
FIG. 21 TYPICAL SINGLE PHASE TRANSFORMER INSTALLATION 
39 


E. M. PART VI-CHAPTER 1-May 1953 
LIGHTNING ARRESTERS 
GROUND WIRE 
SOLDERLESS CONNECTORS 
FIG. 22 
GROUND RODS 
TYPICAL THREE-PHASE TRANSFORMER INSTALLATION. 
OPEN DELTA WITH TAP AT MIDPOINT OF 
ONE TRANSFORMER. 

40 

E. M. PART VI-CHAPTER l__;Maj 1111 
CROSSARMS 
GROUND WIRE IN WOOD MOULDING 
I 
FIG. 23 
TYPICAL THREE-PHASE TRANSFORMER BANK 
3-25 kva OR LESS 
41 

E. M. PART VI-CHAPTER 1-May 1953 
NOTE: INSTALLATION SHOWN 
IS FOR 3 PHASE POWER BANKS 
OF 3·37~ KVA TO 3-150 KVA 
BANKS. FOR BANKS OF LARGER 
CAPACITY OMIT PLATFORM AND 
INSTALL TRANSFORMERS ON 
CONCRETE MAT. 

INSULATED CLEVIS DEAD ENOS 
CONNECTIONS TO BE 
DELTA OR WYE AS REQUIRED. 

r ".., 
F ~ 
!""'

---"' p
~ ~lT 
p 
!<-" 
~ Ia 1 
c t? 
J...., 
r.J \I II> 
0 =~of--
IJ rr rr 
~lc-
~0~ 
5;8 " 0. A. SOL T 
u•-o" APPRox. 
LIGHTNING ARRESTERS 
CUTOUT 
·-·-GROUND WIRE 
2 11 
X 6" X 121-6 11 
ARM BRACECREO. PINE -4 REQ.
TIMBERS 16-CREO. PINE BOARDS 2" X 8 11 X 7'-0" 
~CROSSARM BRACE AT ABOUT 10" O.C. HELD WITH A 
J/1 " X 3 1/2 11 CARRIAGE BOLT IN EACH CHANNEL. 
FIG. 24 
TYPICAL THREE-PHASE TRANSFORMER BANK -3-37}S & LARGER 

42 


E. M. PART VI-CHAPTER 1-May 1953 
OIL SWITCH 
POLE~ 
GROUND WIRE -~IN WOOD MOULDING 
FIG. 25 
/ 
r-STRAIN INSULATOR EACH 
1
SIDE OF ARMS
1
/ 
STREET LIGHTING WIRE EACH SIDE OF ARMS 
PROTECTIVE RELAY 
CONSTANT CURRENT TRANSFORMER 
CONTROL WIRES IN CONDUIT TO 
TIME & MANUAL CONTROL 
SWITCH. 

NOTE: INSTALL ADDITIONAL 
LIGHTNING ARRESTER WHEN 
CONNECTION IS MADE TO TWO 
PHASE WIRES. 

TYPICAL STREET LIGHTING REGULATOR INSTALLATION 
43 

E. M. PART VI-CHAPTER 1-May 1953 
_STRAIN INSULATOR SEE DETAIL BELOW 
~-OPEN WIRING OPTIONAL 
I  
~-- BWP  
I  
I  
I  
2 COND. NO. 1-5 KV-ORNAMENTAL ---• POLE & BRACKET CABLE.  I I I  STRAIN INSULATOR  
I  

TO LAMP TERMINAL 
DUPLEX 
POLE OPEN WIRING 
1% "PIPE 
LUMINAIRE OF TYPE SPECIFIED 161 -0" TO GROUND 
UPSWEEP BRACKET WITHOUT SCROLL OPTIONAL 
FIG. 26 TYPICAL STREET LIGHTING UNIT 
44 

El~ lllQ-345-181 
Change 2 
15 Oct 62 
UNDERGROUND ElECTRICAL 	DISTRIBUTION AND STREET LIGHl'ING SISTE14S 
1-34 GENERAL. Underground electrical distribution should be installed in areas where saf'et7 precautions, such as flight hazards and the use or cranetype material handling equipment, require the use or underground cable. Underground construction should also be utilized within 300 feet or tovers 
containing high frequency-equipment and for all primar7 service connections into buildings. Otherwise underground electrical distribution will be utilized onl7 upon receipt or specific approval from the Office or the Chief of Engineers. 
1-35 DUCT LINES. Duct lines should be installed adjacent to streets or roads wherever practicable, in order to avoid interference with future building foundations. Figure Z7 shows a typical la70ut of duct lines tor an underground electrical distrilntion s,-stem. For uniformit7 symbolsshown on figure 28 should be used to indicate underground construction on drawings. Ib order to encourage competitive bidding, the contractor should be given the option or furnishing either cla,-, fiber, asbestos-cement, precast concrete, or soapstone duct, unless local conditions indicate that it would be more advantageous to the Government to specif7 a definite material. Duct lines tor both primar7 and communication cables should be installed. The communication cables vi11 usual17 be installed b7 the Signal Corps, Air 
Force, or local telephone company, but the designer or the electrical 
distribution s,-stem is responsible for providing the racewa7s wherever the two s,-stems follow the same route. The two s,-stems should be completel7isolated from each other throughout. Design or the duct s79tem for communi
cation cables should be coordinated with the local communication officer. 
The nominal diameter of ducts for primar7 cables should be not less than 4 inches. The nominal diameter of ducts for communication cables should be not less than 3 inches. l~ltiple duct is suitable for communication cables but should not be used for the primar7 s,-stem. Duct lines for the primar7and communication cables should be encased in concrete, with the exception
of multiple duct. A concrete base and cover is sufficient for this type of duct. The concrete should be reinforced under railroad tracks. Figures 29 through 32 show typical cross sections of duct lines. The typical cross sections show the mioimum required concrete encasement. There is no o~ jection to contractors rounding out the encasement to suit trenching con
ditiona. ltinimwn coverage should be 18 inches to top of concrete. All duct lines should drain to manhole with an even grade to avoid water pockets.High point may be either at or between .manholes, depending on· the contour of finished grade. A sufficient number or spare ducts should be installed to provide for the future installation of a 25 percent increase in the initial 
45 	Eng. Man. Part VI, Chap. 1 
El.f lllo-345-181 
Cb.&Dp 2 , 
15 Oct 62 
D.Wilber or cables. The DWilber of spare ducts, should be increased as re
quired for .tnture service to pl.aDned expai)Sion, provided the planned 
*expansion is in a reasoaab!7 definite category. For grounded neutral 
*systems, an insulated neutral cable should be installed in the duct line 

·*vith the pover cable or cables and connected to the ground rod in each ~le. The insulation on the neutral cable should be a polyethylene or *polychloroprene type suitable for direct blrial. A careful study should be made of all other underground utilities in order to insure minimum of conflict between electrical, water, sewer', steam and gas systems. 
1-36 MANHOLES. l~les should be of applicable type shown on figures 34 to 39 inclusive and should be located to provide maximum flexibility for future expansion of the system. In some cases separate manholes are required b,y the Army Signal Officer for communication cables. In these cases the telephone manholes should be constructed in accordance with the applicable details shown on Signal Corps Drawings Nos. FS-D-32722 or ES-D-32759. ·These drawings are available only through the local Signal Corps representative. Stubs for tuture extensions should be provided whenever future extensions are considered probable. l.fanhole hardwares should be similar to that shown on figure 33. Sufficient cable racks should be installed to support properly all cables on both sides of the cable splices. Pulling irons should be installed opposite each duct entrance. Distance between manholes on straight runs should not exceed 600 feet and should not be less than 400 feet except as required for connections and corners and to avoid conflict with streets or other utilities. Distance between manholes on curved sections of duct lines should not exceed 300 teet. A copper or copper-clad steel ground rod 
*should be installed near one corner in each manhole except that where *lead-sheathed cables are installed, zinc-coated-steel ground rods will *be used in lieu of copper-clad rods for grounding purposes. No electrical 
equipment should be installed in m&nholes unless required b,y airfield clearance criteria and unless extension of cables to nearest transformer vault for sectionalizing or tapping is impracticable. l.fetal ladders in manholes will not be required. 
1-37 PRDaR! CIRCUITS. The number of primary circuits should be established on the basis that each circuit will carry the kilovolt-ampere load listed in table IX for the distance indicated, without exceeding a 2 percent voltage drop. The kilovolt-ampere load should be determined b,y adding the kilovolt-ampere rating of all transformers to be connected to the circuit and applying a suitable diversity factor. A diversity factor of 60 percent will be sufficiently accurate for most feeder calculations. This diversity factor should be increased to 100 percent, however, where the circuit will feed a load wherein all of the distribution transformers will be operating at full load at the same time. Where b.rl.lding layout is suitable, primary circuits should be installed in loops with sectionallzing switches at convenient points to insure the supply of electric service to all transformers 
Eng. Man. 46 
Part VI, Chap. 1 

El.f 111~345-181 
Change 2 15'0ct 62 
with any one section of the loop cable cut out. Feeder calculations for loop circuits should be based on the voltage drop to the center of the load on the loop and the loop should be normally open at this point. The abnormal voltage drop which will occur when the load is shifted due to cable failure can be tolerated until the damaged cable is repaired or replaced. Where building layout is not suitable for loop circuits, radial circuits should be installed. Figures 40 and 41 show typical diagrams of loop and radial primary systems, 
Table IX. Three-Phase Primary Circuit Loading. 
LKilowatt capacity of wires and maximum distance in feet to load center for 2 percent voltage drop, underground systems) 
Wire.U.  Kilowal&  IOOI'"f"'D&  KiJowt'&  80-o\  
pfd pf dioloDc:<l  
2,400-volt  

g______________ _ 208 1,020 167 1,020 
282 1,160 226 1,160
6-----------~--
4______________ _ 
366 1,350 293 1,350
2______________ _ 
490 1;500 392 1,500
l_ _____________ _ 
575 1,620 460 1,550 1/0-------------652 1,800 522 1,660
2/0____________ _ 765 1,930 613 1,6903/0____________ _ 870 2,170 695 1,7804/0____________ _ 985 2,400 789 1,850
250____________ _ 
1,130 2,420 905 1,820300 ____________ _ 1,240 3,510 992 1,860350 ____________ _ 1,350 2,760 1,080 1,920
<i()()____________ _ 
1,500 2,960 1,200 1,920 
46a Eng. l.fan. Part VI, Chap. 1 

E. M. PART VI CHAPTER 1 
Wire size Kilowatt 
8_______________ 6_______________ 4_______________ 2_______________ } _______________ 1/0_____________ 2/0_____________ 3/0_____________ 4/0_____________ 250_____________ 300_____________ 350_____________ 400_____________ 
8_______________ 6_______________ 4_______________ 2_______________ 1_______________ 1/0_____________ 2/0_____________ L'~ 
li', 
3/0~-----------
4/0_____________ 250_____________ 300_____________ 350_____________ 400_____________ 
8_______________ 6_______________ 4_______________ 2_______________ 
!_ ______________ 
1/0_____________ 
2j0 _____________ 
3/0_____________ 4/0_____________ 250_____________ 300_____________ 350_____________ 400_____________ 
360 490 634 850 995 1,130 1,320 1,500 1,710 1,960 2,150 2,340 2,600 
415 564 730 980 1,145 1,300 1,530 1,735 1,970 2,260 2,480 2,700 3,000 
62.'3 
846 1,090 1,470 1,720 1,960 2,290 2,600 2,950 3,390 3,720 4,050 4,500 
100 percent Kilowatt pf distance 
4,160-volt 
1,770 2,000 2,340 2,600 2,810 3,130 3,360 3,760 4,160 4,200 4,360 4,790 5,130 
4,800-volt 
2,040 2,310 2,700 3,000 3,240 3,600 3,860 4,340 4,800 4,850 5,020 5,500 5,920 
I 
7 ,200-volt 
3,060 3,470 4,040 4,520 4,870 5,410 5,810 6,520 7,200 7,280 7,530 8,280 8,900 
288 
392 506 
680 
795 
905 
1,060 
1,200 
1,370 
1,570 
1,720 
1,870 
2,080 
332 450 584 784 915 1,040 1,222 1,385 1,572 1,810 1,980 2,160 2,400 
498 676 872 1,175 1,375 1,570 1,8.'30 2,040 2,360 2,710 2,980 3,240 3,600 
May 1953 
80 percent pf distance 
1,770 2,000 2,340 2,600 2,700 2,880 2,930 3,080 3,210 3,170 3,230 3,:330 3,330 
2,040 2,310 2,700 3,000 3,110 3,320 3,380 3,550 3,700 3,650 3,720 3,840 3,840 
3,060 3,470 4,040 4,500 4,670 4,980 5,080 5,320 5,560 5,490 5,590 5,770 5,770 
47 

E. M. PART VI CHAPTER 1 
May 1953 
Wire size Kilowatt 	100 percent Kilowatt 80 percentpf distance pf distance 
12, 000-volt 
8_______________ 
1,040 5,090 	832 5,0906 _______________ 
1,410 5,770 1,130 	5,7704 _______________ 
1,830 6,740 1,460 	6,7402 _______________ 
2,450 7,520 1,960 	7,5001 _______________ 
2,870 8,110 2,300 7,7601/0_____________ 
3,260 9,030 2,610 	8,3002/0_____________ 
3,820 9,680 3,060 	8,4403/0_____________ 
4,350 10,850 3,480 	8,8904/0_____________ 
4,930 12,000 3,940 9,250250_____________ 
5,650 12,100 4,520 	9,110300_____________ 
6,210 12,550 4,960 	!l,300
350_____________ 
6,750 13,800 5,400 	9,600400_____________ 
7,500 14,800 6,000 	9,600 
13,800 volt 
8_______________ 
1,193 5,860 	!l55 5,8606 _______________ 
1,622 6,650 1,300 	6,6504 _______________ 
2,100 7,750 1,680 	7,7502 _______________ 
2,820 8,660 2,250 	8,6301 _______________ 
3,290 9,320 2,630 	8,9401/0_____________ 
3,750 10,400 3,000 	9,5502/0_____________ 
4,400 11,100 3,520 	9,7103/0_____________ 
5,000 12,500 4,000 	10,2204/0_____________ 
5,650 13,800 4,520 	10,650250 _____________ 
6,500 13,950 5,200 	10,500300_____________ 
7' 150 14,500 5,710 	10,700350_____________ 
7,760 15,900 6,200 	11,000
4()()_____________ 
8,620 17,000 6,900 	11,000 
Notes. 1. All voltages are line to line. 
2. 
Wire capacities are for V.C. wires in duct. 

3. 
To compute the maximum distance to a load center with 2 percent voltage drop for connected loads not listed above: 


a. Select from the table the desired wire size which will car1·y the load at the applicable voltage rating. 
b. 
Multiply the "kilowatts" given in the table by the "distance" given in the table, for the selected wire size. 

e. 
Divide this product by the actual load in kilowatts. 

d. 
If the computed distance is not adequate, select a larger wire size and J"epeat the calculation. 


respectively. Either a loop or two radial feeders should be available for use at all hospital transformer banks, to insure a continuous supply of electricity during inspection and repair operations, unless the cost involved is inconsistent with the cost of the project under design. Primary cable installed in duct lines should be of the varnished cambric-insulated leadcovered, paper insulated lead-covered or polychloroprene-sheathed type, with bare neutral conductor where required for 4-wire systems. Primary cable buried directly in the ground should be of the polychloroprene-sheathed or metallic armored type. Direct burial cable should not be utilized in areas where mechanical damage is considered likely or where the cable will be inaccessible for replacement. Minimum coverage for direct burial cable should be 2 feet. 
48 

E. M. PART VI CHAPTER 1 May 1953 
1-38 SECONDARY CIRCUITS. Secondary circuits should be installed in metal or nonmetallic conduit where subject to mechanical damage and under paved areas. Where mechanical damage is considered unlikely, such as in housing areas, the cable not under paved areas should be buried directly in a treach. Metal conduit, when used, should be painted with heavy asphaltum, tar or equivalent before being covered. Minimum coverage for conduit should be 18 inches. Minimum coverage for direct burial cable should be two feet. Splices and taps below ground should be kept to a minimum. Where one secondary feeder supplies service to more than one building, the necessary connections should be made in junction boxes mounted on the buildings as shown in figure 4Z or in Type D manholes as shown on figure 43, depending upon the size and number of cables involved. The following maximum wire loading is recommended for secondary cables, based on a 55° C. temperature rise above a zoo C. earth temperature, provided the voltage drop given in paragraph 1-39 is not exceeded : 
Size AWG Amperes MCM size Amperes 
8-------------------------60 250 275 
6________________________ _ 
77 300 310 
4________________________ _ 100 350 340 
2 ________________________ _ 131 400 363 
1 ________________________ _ 
150 500 412 
1/0______________________ _ 170 600 4552/0______________________ _ 
192 700 494 3/0-----------------------, 
218 750 512 
4/0 ______________________ _ 248 800 530 
For ambient earth temperatures other than zoo C., the current-carrying capacities listed above should be multiplied by the following factors : 
Ambient temperature Multiply by 
10° c. 1.09 30° c. 0.90 40° c. 0.79 50° c. 0.68 
1-39 VOLTAGE DROP. Voltage drop should not exceed 2 percent on the primary and secondary circuits respectively. 
1-40 TRANSFORMERS. Transformer banks having a total capacity of 150 kilovoltamperes or less should comprise conventional single-phase transformers. Figures 44 through 46 show typical conventional transformer installations. Transformer banks having a total capacity of ZZ5-to 501-kilovolt-amperes should comprise conventional single or three-phase transformers or factory-assembled transformer load centers as determined by the cost of installation and suitability for the project. Larger transformer installations should consist of factoy-assembled transformer load centers comprising a high voltage section, transformer section, and low voltage section, unless single-phase transformer banks are specifically requested bx the using service. Figures 47 and 48 show typical layouts of liquid-cooled and air-cooled transformer load centers, respectively. The use of transformer banks comprising double-ended transformer load centers as shown on figures 49 and 50 is limited to large 
49 

EM 1110-345-181
Change 1
24 Jun 57 

hospitals and other equally critical loads where fast, automatic transfer is essential.
Transformers should be located as close to the center of the secondary load as practicableand should preferably be located in buildings. Where the installation of transformers inbuildings is not practicable, such as in housing areas, the transformers should be installedon outdoor, fence-enclosed, concrete foundations, except where the installation includesopen primary wiring which may be hazardous to children in the area. Where open primarywiring is utilized in housing areas, the installation should be enclosed in a small building.Careful consideration should be given to the location of outdoor installations in order thatthe equipment and enclosure will be as inconspicuous as possible and, with the additionof shrubbery, will fit properly into the landscaping layout. Transformers should be of theself-cooled type, with rating selected from table I. When the required size is not listed inthe table, the next larger size should be installed, unless the next smaller size will provideat least 90 percent of the required rating. Wye-wye connected transformers should not beutilized on systems wherein the primary neutral conductor is not installed or within 500feet of radio stations and navigational aid facilities. Transformers installed in fireprooftransformer vaults or outdoors should be of the oil-insulated, self-cooled type. Transformersinstalled within buildings in which fireproof vaults have not been provided should be ofthe nonflammable-liquid-cooled type. 
Transformercapacities should be selected so that all transformers will be operating as nearly as practicableto the allowable temperature limits during periods of maximum demand. In general, thecapacity of transformers should be equal to approximately 60 percent of the connected load,exclusive of family quarters. The transformer capacity for each installation, however, y.rillrequire special study and will vary from a demand factor of 30 percent for large hospitalbuildings to a demand factor of 100 percent for isolated power installations. Demand factorsfor family quarters, with or without electric ranges and water heaters, are listl:'d inparagraph 1-29. 
1-41 STREET LIGHTING SYSTEM. Street lighting system should be 6.6-or 2U-ampereand should employ complete metallic loops. Transformers and control equipment should belocated in transformer vaults. Table VIII lists the number of group replacement straightseries lamps with film cutout which can be connected to each standard size regulator. Thecapacity of regulator for mixed loads comprising a number of 2,500 lumen lamps and anumber of 4,000 h1 men lamps may be determined by adding the size regulator requiredfor the 2,500 and 4,000 lamps, respectively. Street lighting regulators should always beas fully loaded as practicable since the primary power factor drops sharply under light loadconditions. Supplementary multiple lights may be used on 6.6-ampere systems, in whichcase insulating transformers with multiple secondary windings should be employed. Bothautomatic and manual control should be provided. Automatic control should be by meansof time switch equipped with astronomical dial. Manual control should be by means ofrush button station located on the outside of wall or fence enclosing the regulator. Provisionshould be made to prevent the operation of push button station by unauthorized persons.Street lighting cable should be installed in nonmetallic conduit where subject to. mechanicaldamage and under paved ar<:as. Where mechanical damage is considered unlikely, the cablenc•t under paved areas shr;uld be buried directly in a trench. Minimum coverage should be.l :3 inches. Typical lay(mt of underground street lighting system is shown on figure 51. 
50 
E. M. PART VI CHAPTER 1 
May 1953 
1-42 STREET LIGHTING UNITS. Street lighting units should consist of concrete, 
steel or aluminum standards and pendent-type luminaires similar to those shown on figure 52. The styl~-of standard and luminaire should be selected to harmonize with the type of architecture of surrounding buildings. Selection should be coordinated with the principal architect in the division or district office concerned with the design of the system. Lighting intensities should be based on the installation of 4,000 lumen lamps spaced 150 to 200 feet apart in administration, recreation and hospital areas, and 2,500 lumen lamps spaced 150 to 200 feet apart in quarters, barracks, industrial, warehouse, utility and stqrage areas. These spacings should be measured along the center line of streets designed for two or three lanes of traffic and along each side of streets designed for more than three lanes of traffic 
and along streets having parkways in the center. One street lighting unit should be installed at each intersection designed for two or three lanes of traffic and two street lighting units at each intersection designed for more than three lanes of traffic and streets having parkways along the cent~r. 
51 

E. M. PART VI-CHAPTER 1-May 1953 
~-··· 

0 ::: SECONDARY JUNCTION BOX 
FOR SYMB

@ NUMERAL OLS, SEE FIG. 2d 
IN CIRCLE INDICATES TRANSFORMER VAULT NUMBER 
lYriCAL LAYOUT FIG. 27 
UNDERGROU 
DISTRIBUTION SY~~E;LECTRICAL 
52 

E. M. PART VI-CHAPTER 1-May 1953 
, ~ ~ 2-T 
3 #2 
--------'-

___2_#2-
3#2-1Y,"C 
3#2-1Y, 11 C 
MANHOLE -TYPE AS INDICATED -SEE DETAILS. 
TRANSFORMER VAULT STREET LIGHTING STANDARD. 
CAST IRON WEATHERPROOF SECONDARY JUNCTION BOX MOUNTED 11-0" ABOVE GRADE (12" X 12" X 6" UNLESS OTHERWISE INDICATED). 
DUCT LINE -NUMBER OF DUCTS AS INDICATED. E =ELECTRIC -T =TELEPHONE. 
SERIES STREET LIGHTING CABLE BURIED IN TRENCH -SINGLE CONDUCTOR -OF SIZE INDICATED. 
SINGLE-PHASE SECONDARY CABLE BURIED IN TRENCH -NUMBER AND SIZE OF CONDUCTORS AS INDICATED. 
THREE-PHASE SECONDARY CABLE BURIED IN TRENCH -NUMBER AND SIZE OF CONDUCTORS AS INDICATED. 
SINGLE-PHASE SECONDARY CABLE INSTALLED IN CONDUIT -NUMBER AND SIZE OF CONDUCTORS AND SIZE OF CONDUIT AS INDICATED. 
THREE-PHASE SECONDARY CABLE INSTALLED IN CONDUIT -NUMBER AND SIZE OF CONDUCTORS AND SIZE OF CONOUIT AS INDICATED. 
FIG. 28 STANDARD SYMBOLS UNDERGROUND ELECTRICAL DISTRIBUTION CONSTRUCTION 
53 

E. M. PART VI-CHAPTER 1-May 1953 
r------------------------------------------------------------------------------------~ 
.1 II !
-6"
r-6" -1 
-----r • . 0. ,6 ~. ·,
J
6" 
.. .. 
___l ~. l'·. I> ,) .. -.· . ·" 6" I A. 
c
•!'J " 
(}
p 
0-:.0d 0 ' 
c
~ .. . L\ 
3" ~ r---' . . . h . .f:, 
3" .~ NO. 8 WIRE 
.o·o .B
.fj 4 
• ,, 
HOOPS APPROX.
·~0 0
. /, .. . ~ 
8" o.c.
T ,._ ~ .i 
6" 6"
··-. • 
. ~ 
. • A ~ :_, . 'D ..
~ ' __L 
TYPICAL SECTIONS OF REINFORCED DUCT LINE INCASEMENT. USE UNDER ALL RAILROAD TRACKS AND AS OTHERWISE NOTED ON DRAWINGS. REINFORCED INCASEMENT TO EXTEND AT LEAST 15 FT. ON EACH SIDE OF 4_ OF RAILROAD TRACKS. 
3" A 3" 
ho~o· 
2WAY 3WAY 
.------t-=----;: ¢
b 0 ". 
INSTALL EDGEWISE BETWEEN MANHOLE) . ~ .. 0. Jl'
3" 
( AND SPLAY OF JOINT-USE DUCT LINE 4 WAY 
6 WAY 9 WAY 
SINGLE DUCTS FOR ELECTRIC OR TELEPHONE CABLES. FOR JOINT CONSTRUCTION SEE DETAILS APPLICABLE TO DESIRED COMBINATION (FIGS. 30, 31, & 32). 
NOTES-DIMENSION A= 1Y, "FOR CLAY OR SOAPSTONE DUCT AND 2" FOR FIBRE OR ASBESTOS CEMENT DUCT. ALL DIMENSIONS ARE MINIMUM FROM OUTSIDE SURFACE OF DUCT. CONCRETE NOT REQUIRED BETWEEN HORIZONTAL FACES OF CLAY DUCT. 
FIG. 29 
TYPICAL SECTIONS OF DUCT LINES 
54 

E. M. PART VI-CHAPTER 1-May 1953 
...
~ 
. 
"..) ..0 
DO " 
DO 
DO 
2 WAY 	~ .· ~· .. 
,, 
<'> 3 WAY 6 WAY EDGEWISE CONSTRUCTION (FOR USE ONLY BETWEEN MANHOLE AND SPLA'; OF JOINT-USE DUCT LINE.) 
·[ ',4' ·~.· ·?
3 d .. fJ" .·
311~~;,-·,o:j_ .. _·o,
·.···(1 .. 
00 	DO 

3';r ...·. .u·... ·tf . ·. a . . .;:f. _L ·.·.·.· .. '.6: 
·D 
DO 
2 WAY 3 WAY 4 WAY 
t·.··.
0 •' ·<> 	-4 
·o ' ., 	r ./· ·' 
[\·· .< 	,.,· 
DOD 	[JOO

ODD 	OCJO 

I, ' .1· ·. "·· 
-~·· • ."1~ 
DOD
6 WAY 
. -~\ ~ 
... 
e 	. . . '·1 9 WAY 
MULTIPLE DUCTS FOR TELEPHONE CABLE NOTE: ALL DIMENSIONS ARE MINIMUM FROM OUTSIDE SUflFACE OF DUCT. 
FIG. 30 TYPICAL SECTIONS OF DUCT LINES 
55 

E. M. PART VI-CHAPTER 1-May 1953 
I
H ... 
4 11 i3 11
. I 
... 4" 
311' 
~-j__L.__:__:____:__J 
SINGLE DUCT 	MULTIPLE DUCT 
2 WAY ELECTRIC -2 WAY TELEPHONE 
' !
I .... I 	1 Jll : 4"
.._
r---
) I . '. ' i -. 
~:n·.b 
-~:o·.,.ob, 
~--,----o·• l---" 3" 
I ' 
! • . ! . 
··L ., . 
~ 
SINGLE DUCT 	MULTIPLE DUCT 
3 WAY ELECTRIC -2 WAY TELEPHONE 
II 
311' 
I 
SINGLE DUCT 	MULTIPLE DUCT 
3 WAY ELECTRIC -3 WAY TELEPHONE 
NOTES: 	DIMENSION "A" =-1 y,u FOR CLAY OR SOAPSTONE DUCT AND 2" FOR FIBRE OR ASBESTOS CEMENT. ALL DIMENSIONS ARE MINIMUM FROM OUTSIDE SURFACE OF DUCT. CONCRETE NOT REQUIRED BETWEEN HORIZONTAL FACES OF CLAY DUCT. 
FIG. 31 
TYPICAL SECTIONS OF DUCT LINES 

56 
E. M. PART Vl-CHAPTER-1--May 1953 
3"' z... 
L.
~-L-~~-----~--------~~~~ 
SINGLE DUCT MULTIPLE DUCT 4 WAY ELECTRIC -2 WAY TELEPHONE 
_ _L_A 
~wb~----------~
3;;r 
'---1!----~-------' __.___ 
SINGLE DUCT MULTIPLE DUCT 4 WAY ELECTRIC -3 WAY TELEPHONE 
3" -~A~ 
4".• 
----.. 
Jll ~ ~-... -~ 
• 
A . 
-~
qlb, 
A DO
A J5 -A 
t 
0·0 ADD 
~ 
~ A .6--/).-t, -~ A 
SINGLE DUCT MULTIPLE DUCT 4 WAY ELECTRIC -4 W.AY TELEPHONE 
NOTES: 
A=l~" FOR CLAY AND SOAPSTONE DUCT AND 2" FOR FIBRE OR ASBESTOS CEMENT. 
ALL DIMENSIONS ARE MINIMUM FROM OUTSIDE SURFACE OF DUCTS. 
CONCRETE NOT REQUIRED BETWEEN HORIZONTAL FACES OF CLAY DUCT. 

FIG. 32 
TYPICAL SECTIONS OF DUCT LINES 

57 

E. M. PART VI-CHAPTER 1-May 1953 
SEE NOTE "B" 
lli" TO~" 
LETTER BLOCKS 1\4" WIDE 6 RIBS TAPER
211 
HIGH LETTERS lit" WIDE 
COVER 	%" TO ~" 
FRAME 
U.S. 	STANDARD HEX. NUT ANO COTTER 
,. I 
COVER HMCOLES 2 REQUHtED 
lr "" ·i •·-1 f;w 000000 Tl 
PaltCELAIN INSULATORS 
DDDDDD ~,~! ... 000000 ~
<11.<0-
SUMP FRAME AND COVER 
CABLE RACK FASTEN BY MEANS OF2~" X ~" BOLTS AND EXPANSION SHIELDS. 
NOTE "A" FOR PAVED AR£A'5 SUR'JECT
-H-7/1"
I 
TO TRAFFIC THESE DIM£1NSIOM5 
TO BE 2" IN LIEU OF I 3/1", 
I 
~MANHOLE WALL NOTE "B" 
USE THE WORD SIGNAL FOR 
TELEPHONE MANHOLES. 

I 

FIG. 33 
MANHOLE HARDWARE 
58 

E. M. PART VI-CHAPTER 1-May 1953 
FINISHED GRADE 
b :.A.
J ~~
1 ". 
CABLE RACKS ~
l I Il·
. ·, GROUND ROD .. ! . 
3" 
SECTION A-A 
TYP!t:AL REINFORC911Et4T OF MIP 11-611 41-011 
GROUND THICKNESS OF CONCRETE: ROD MANHOLE WALLS, TOP AND BOTTOM .........................&'! 11-6" 1'·6" SUMP WALLS AND BOTTOM ...6 1! 
REINFORCING BARS:~ u ROUND, I
PLAN 
DEFORMED. WALLS & BOTTOM APPROX. · 12 11 C. TO C BOTH •a.YS. TOP AS SHOWN. 
FIG. 34 
TYPE "A" MANHOLE 
59 
E. M. PART VI-CHAPTER 1-May 1953 
SECTION A-A 
TOP 
6'-Qll 
0 
51 0 11 
THICKNESS OF CONCRETE: • 
MANHOLE WALLS, TOP AND BOTTOM....8'! 
SUMP WALLS AND BOTTOM......•.....••...•.611• 
PLAN 

REINFORCING BARS: l'.! 11 ROUND, DEFORMED. WALLS & BOTTOM APPRox: 12" C. TO C. BOTH WAYS. TOP AS SHOWN. . 
FIG. 35 
TYPE "B" MANHOLE 
60 
E. M. PART VI-CHAPTER 1-May 1953 
SECTION A-A 
THICKNESS OF CONCRETE: MANHOLE WALLS, TOP AND BOTTOt.\.............8". SUMP WALLS AND BOTTOt.\.........•...........6 11• E. M. PART VI CHAPTER 1 SEPT. 1952 
TELE HONE 
EB z 
i 
3" 
REINFORCING BARS: ~" ROUND, DEFORMED. WALLS & BOTTOM APPROX. C. TO C.
1211 BOTH WAYS. TOP AS SHOWN. 
ELECTRIC 
FIG. 36 
TYPE "C" MANHOLE 

61 


E. M. PART VI-CHAPTER 1-May 1953 
FINISHED GRADE 
ll 
l ... r 
3" 
SECTION A-A 
TYPICAL REINFORCEMENT OF TOP 
GROUND ROD 
'4~==~---------------------+J, ; 
~~~~~--------~6~·-~0~"------------+:·~ 
PLAN 
REINFORCING BAR: ~" ROUND, DEFORMED. 
THICKNESS OF CONCRETE:WALLS & BOTTOM APPROX. 12" C. TO. C. 
MANHOLE WALLS, TOP AND BOTTOM..........811•

BOTH WAY. TOP AS SHOWN. 
SUMP WALLS AND BOTTOM......................•..6". 

FIG. 37 
TYPE "E" MANHOLE 
62 

E. M. PART VI-CHAPTER 1-May 1953 
TOP 
SECTION A-A 
~---_!'.·~----~ 
I 
A 
GROUND ROD---+--~ 
THICKNESS OF  CONCRETE:  REINFORCING BARS:  ~" ROUND,  
MANHOLE  WALLS,  TOP  AND  BOTT0\1...8".  DEFORMED.  WALi..S & BOT> OM  
SUMP  WALLS AND  BOTTOM..................6".  APPROX.  12" C.  TO C.  BOTH  
WAYS.  TOP  AS SHOWN.  
PLAN  

FIG. 38 
TYPE "F'' MANHOLE 

63 

E. M. PART VI-CHAPTER 1-May 195S 
THICKNESS OF CONCRETE: MANHOLE WALLS, TOP AND BOTTOM.....•......•.....................&". SUMP WALLS AND BOTTOM....•..6". 
REINFORCING BARS: ¥.!" ROUND, 
DEFORMED. WALLS & BOTTOM APPROX. 
12 11 
C. TO. C. BOTH WAYS. TOP AS SHOWN. 
PULLING IRONS 
A 
t 
PLAN 
TYPICAL REINFORCEMENT OF TOP FIG. 39 
TYPE "G" MANHOLE 
E. M. PART VI-CHAPTER 1-May 1953 
TAP TO STREET LIGHTING REGULATOR OR AERIAL CIRCUIT 
SECTIONALIZING SWITCH PRIMARY LOOP CABLE 
INCOMING SERVICE ~ FEEDER C/8( = 
FIG. 40 
TYPICAL UNDERGROUND LOOP SYSTEM 

65 
E. M. PART VI-CHAPTER 1-May 1953 
r1l 
I~ I
IT, 
LlJ 
---, 
~--1t-j 
--:-1 
~~I
L_ __ _j 
TRANSFORMER UNIT 
PRIMARY FEEDER #l 
--~
'4tJ
r 
L_ __
PRIMARy FEEDER #2 
INCO...
"·"HG SERVICE 
FE_E_D~ER~CJa7
l_______ __ 
FIG.41 M 
TYPICAL UNDERGROUND RADIAL SYSTE 
66 
E. M. PART VI-CHAPTER 1-Mav 1963 
APPROX. 1'-0"  -CAST IRON JUNCTION BOX CONDUIT FITTING  
CONDUIT ELLS  SECTION  BUILDING WALL  
BUILDING WALL  

ELEVATION 
NOTE: JUNCTION BOX SHOULD BE SURFACE-MOUNTED ON EXISTING BUILDINGS. 
FIG. 42 
TYPICAL SECONDARY JUNCTION BOX 

67 
B. M. PART VI-CHAPTER 1-May 1953 
I 
I 
_l 
PLAN SECTION A-A 
FIG. 43 
TYPE "D" MANHOLE FOR LOW VOLTAGE CABLE ONLY 

68 
E. M. PART VI-CHAPTER 1-May 1953 
VENT 
PRIMARY BUS BUS SUPPORT 
t?ttt1 Et 
VENT 
SINGLE PHASE TRANS 
3 PHASE,/ 
4 WIRE 
SECONDARY 
BUS 


S-IN-~:.-A-SE---
TRANSFORMER 
I I I 
ELEVATION 

''"~ ,~,,-

TRANSFORMER 
VENTS IN 
WALL OR 
WINDOW 

~-~ 
SONG~ ,.." -l....-+--~'I 
BUSTRANSFORMER 
LOW VOLTAGE DISTRIBUTION CENTER 
TYPICAL INDOOR CONVENTIONAL TRANSFORMER INSTALLATION FOR 3 PHASE, 4 WIRE SECONDARY 
69 

E. M. PART VI-CHAPTER 1-May 1953 
BUS SUPPORT 
CONCRETE 
~/f I 
FINISHED GRADE r-'-'---------i ~· 
. ·'' ,t .. 
~\ 'c-..· 
ELEVATION A-A 
CHAIN LINK FENCE 
SINGLE PHASE 
TRANSFORMER 

A 
SECONDARY 
SWITCH OR 
PANEL 

------------->1((-----
FIG. .CS 
TYPICAL SINGLE PHASE OUTDOOR CONVENTIONAL TRANSFORMER INSTALLATION 
70 
E. M. PART VI-CHAPTER 1-May 1953 
. _....,_ ----------·------------· _,_. -----'1(----
..__,.._ 
-
... 
--7
-· 
'"':::'
~4>~ ~OTHEAD 
"' ~ w Dhe. ¢~ ~ :/ 
~PRIMARY
r1, r.... r-1 
FUSE V BUS ~SUPPORT 
iluv 
~ 
\~~ 
........ 

= 
~~ I@ ~~ PIPE
f Cf J 
SUPPORT 
/J/ 
jj
II 't-~ i 
II i' I 
II ACRErr 
IL--1 ___L 
L 4 il
Ji ~~ 
....6.
o ..
t::.. il 
. ·. <l .l .:\, / 
~»ieo:.-. II .. C. ~ 
ELEVATION A-A 
FINISHED GRADE 
SINGLE PHASE SINGLE PHASE TRANSFORMER TRANSFOitMER 
A 
l 
(tilllN LINK FENCE SECONDARY SWITCH OR PANEL 
L.____ • ---~---~---------6:=~~-------_--_---__._____________, 
FIG. 46 
TYPICAL THREE PHASE OUTDOOR CONVENTIONAL TRANSFORMER INSTALLATION 

71 
E. M. PART VI-CHAPTER 1-May 1953 
PRIMARY SECTION 
FOR RADIAL CIRCUITS USE DISCONNECTING SWITCHES. FOR LOOP CIRCUITS USE 3·WAY SWITCHES WITH TIE BUS AND TWO SETS OF LINKS. FOR LOADS lOOOKVA OR LESS USE LOAD BREAK TYPE FUSED SWITCHES.. FOR LOADS GREATER THAN 1000 KVA, INTERLOCK SWITCHES OR USE CIRCUIT BREAKERS. 
TRANSFORMER  
S~N  SECONDARY SECTION  
~  

ELEVATION 
~ FENCE FOR OUTDOOR INSTALLATIONS ~ 
~--------~.ec....'['""'"rV1 
I ·-~R~D~S 
I 
C• --; 

PRIMARY TRANSFORMER
I SECTION " SECTION 

I y 
I 
/j 
SECONDARY SECTION FLOOR OR 
CONCRETE BASE 
I 
L---·~ / _____ J 

~PLA.(' 
FIG. 47 T't'PICAL LIQUID-COOLED TPANSFORMER LOAD CENTER 
72 


E. M. PART VI-CHAPTER 1-May 1953 
PRIMARY SECTION FOR RADIAL CIRCUITS USE DISCONNECTING SWITCHES FOR LOOP CIRCUITS USE 3-WAY SWITCHES WITH TIE 
\ 
BUS AND TWO SETS OF LINKS
\ FOR LOADS 1000 KVA OR LESS USE LOAD BREAK 
TYPE FUSED SWITCHES 
FOR LOADS GREATER THAN 1000 KVA, INTERLOCK 

SWITCHES OR USE CIRCUIT BREAKERS 
r \ 
i TRANSFORMER SECONDARY SECTION 
90 11 
SECTION ----
I 
.., 
.. ., .· 18 11 "'\ 
~ . .. BUS TRANSITION SECTION 
~ 
ELEVATION 
VENTS WHEN UNIT IS INSTALLED ----~ IN SEPARATE ROOM (NEAR FLOOR AND CEILING) 
I 
I 
PRIMARY TRANSFORMER 
l 72" 
SECTION SECTION 
I 
L SEC0 NOARY sECTION 
WALL OF BUILDING OR WIRE ENCLOSURE 
~AN 
FIG. 4B 
TYPICAL AIR COOLED TRANSFORMER LOAD CENTER 
73 
E. M. PART VI-CHAPTER 1-May 1953 
~  
I  
l  
~I  
0  
,e~, I \\  0 "'  
I  \  
p  \\  
~  \  

TRANSFORMER ROOM FLOOR PLAN 
NO SCALE 

ONE LINE 
WIRING DIAGRAM 
NO SCALE 

A INCOMING SERIVCE·TWO FEEDERS PREFERRED. 
8 TIE BUS, INSTALL WHEN ONLY ONE FEEDER IS AVAILABLE. 
C SPARE DUCTS. 
D PULL 80)(. 

E MAIN CIRCUIT BREAkERS. 

F PRIMARY CABLE IN DUCT. 

G THREE-PHASE TRANSFORMER. 

H SECONDARY SWITCHGEAR SECTION. 

J SECONDARY BREAKERS WITH AUXILIARY ALARM CONTACTS. 

I( TIE BREAKER INTERLOCKED WITH MAIN BREAKERS. 

L SECONDARY FEEDERS. 

M CABLES TO OTHER LOAD CENTERS, IF REQUIRED. 

N DUCTS FOR CABLES TO OTHER LOAD CENTERS, IF REQUIRED. 
P ALTERNATE ROUTE OF ONE PRIMARY FEEDER FOR TAPS TO OTHER BUILDINGS, IF REQUIRED. 
R JUNCliOH BOX AND OIL FUSE CUTOUTS OR LOAD-BREAK FUSED DISCONNECTS, IF REQUIRED FOR TAP. 

S STREET LIGHTING TRANSFORMER. 

T llEMOVABLE WIRE PARTITION. 

FIG. 49 
TYPICAL DOUBLE-ENDED TRANSFORMER LOAD CENTER WITH PRIMARY CIRCUIT BREAKERS 
74 

E. M. PART VI-CHAPTER 1-May 1953 
lr-0 

TRANSFORMER ROOM FLOOR PLAN ONE LINE
NO SCALE WIRING DIAGRAM 
NO SCALE 
A INCOMING SERVICE. 

G THREE-PHASE TRANSFORMER. 

H SECONOARY SWlTCMGEAR SECTION. 

J SECONDARY BREAKERS WITH AUXILIARY ALARM CONTACTS. 
K TIE BREAKER INTERLOCKED WITH MAIN BREAKERS. 

L SECONDARY FEEDERS. 

M CABLES TO OTHER LOAD CENTERS, IF REQUIRED. 
N DUCTS FOR CABLES TO OTHER LOAD CENTERS, IF REQUIRED. 
P ALTERNATE ROUTE OF ONE PRIMARY FEEDER FOR TAPS TO OTHER BUILDINGS, IF REQUIRED. 
R JUNCTION BOX AND OIL FUSE CUTOUTS OR LOAD-BREAK FUSED DISCONNECTS. IF REQUIRED FOR TAP. 

U REMOVABLE WIRE PARTITIONS. 

FIG. 50 
TYPICAL DOUBLE-ENDED TRANSFORMER LOAD CENTER WITHOUT PRIMARY CIRCUIT BREAKERS 
75 


E. M. PART VI-CHAPTER 1-May 1953 
2 .... IHFANTRY REGIMENT 
FAMILY RECREATION 
FOR SYIIBOLS -SEE FIG. 28 
@ ~NS~~~~ti;~~~:s 
FIG. 51 
TYPICAL LAYOUT UNDERGROUND STREET LIGHTING SYSTEM 
76 

E. M. PART VI-CHAPTER 1-May 1953 
BRACKET·!:AN VARY FROM 4FT.T08FT. 
BRACKET CAN VARY FROM I" F't TO~ I 
611 
DIAM 
w 
<( 
"' 
a:l 
0: 
w ::E 
~ 
I
LL 
Dl~. VARIES WITH HEIGHT FROM 811 
TO 911 
GROUND LINE 
CONCRETE STANDARD 
DOOR OPENING 
3 11-511 
JC 8~ .. 
GROUND LINE 1
.C'-O"l 
H 
CONCRETE 
FOOTING 
LL 
z
0:<( 	"' 
<(
0~ 	0: I
..J::E 
W:::l 
I
:::1
... wz-	0 
X '..J !::: 
"'~ 
31: w
L 
~ 
..J 
a 
z 
:::1
TRANSFORMER 0 
0:
BASE 
Cl 
_L 
DOOR OPENING 311-511 8% 11
X 
GROUND LINE 
ANCHOR BOLTS 
w 
~ 
a:l 
0: w ::E 0: 0 IL 
~ 
<( 
0: I-
X 
!::: 
31: 
w 
~ 
..J 
a 
z 
:::1 
0 
0: 
Cl 
1011 
BOLT-DOWN BASE 
PRECAST-BUTT BASE 
FIG. 52
i 
I 	TYPICAL STREET LIGHTING STANDARDS 
L 
77 

E. M. PART VI 
CHAPTER 1 
May 1953 

FLOODLIGHTING OF AREAS 
1-43 GENERAL. Floodlights should be provided as required for the purpose of lighting open storage areas, swimming pools, airplane service aprons, service areas at filling stations, loading platforms, parking areas at theaters, etc. 
1-44 WIRING SYSTEMS. Multiple systems should be utilized for floodlighting. Where the number and size of floodlights will permit, the wiring should be connected to the interior system of an adjacent building or to an exterior secondary distribution circuit. Where a substantial quantity of power is involved, a primary distribution system circuit should be extended to the area and transformers provided at suitable locations. Control should be by means of low-voltage switches or circuit breakers. Switches should be of the fused type unless the wiring is connected to a fused circuit. Primary wiring should be of the same type as the primary system to which it is connected, unless material handling, flying hazards, or other local conditions indicate that a change in the type of system is necessary or is desirable to effect economy. Aerial and underground circuits should comply with the requirements of paragraphs 1-26 and 1-37 respectively. 
1-45 LIGHTING UNITS. Lighting units should consist of adjustable type floodlights mounted on buildings, poles, or towers as required to provide a uniform distribution of light over the area to be lighted. The floodlights should be mounted on buildings or distribution system poles wherever this method of mounting will serve the desired purpose. Floodlight towers, where required, should be made of steel and should be grounded at the base. The location and mounting height of each lighting unit should be carefully selected to avoid objectional glare. The number, size, location, mounting height and beam characteristics of floodlights should be such as to provide a uniform distribution of light over the entire area, with a minimum of waste light against buildings and in unused areas. Lighting installations complying with the following criteria will give satisfactory results for most applications: 
a. 
Open storage areas. Open storage areas subject to night operation should be provided with approximately %-to 1-foot candle at the working level. 

b. 
Paved a:reas around swimming pools. Lighting level should be approximately 3-to 5-foot candles for the pool and adjacent paved area. Floodlights should be spaced approximately 100 to 120 feet apart around the perimeter of paving. 

c. 
Airplane service aprons. For service aprons subject to night operations, floodlight banks, each consisting of three 1,500-watt floodlights, spaced approximately 150 feet apart should be installed along the top of exterior wall of hangar and on wood poles or steel towers located approximately 125 feet from the edge of apron where hangars do not occur. Special consideration must be given to airfield clearance criteria when selecting the location and mounting height of the floodlight banks. Airfield clearance criteria is contained in Air Force Regulations 86-1, 86-3 and 86-5. 

d. 
Service areas at fill'ing stations. Service areas at filling stations should be provided with approximately 7-to 10-foot candles of light on that portion of the area which is actually used for servicing cars at night. 

e. 
Loading platforms. Loading platforms subject to night operations should be provided with approximately 5-foot candles of light at the working level. 

f. 
Parking areas at theaters, etc. Parking areas at theaters and other similar buildings regularly used for night activities should be provided with 200-watt floodlights spaced approximately 100 feet apart adjacent to the parking areas. Floodlights should be omitted in areas adequately lighted by the street lighting system. 


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E. M. PART VI CHAPTER 1 May 1953 
PROTECTIVE LIGHTING SYSTEMS 
1-46 GENERAL. Protective lighting systems should be installed where the lighting of boundaries for the purpose of deterring trespassers and making them visible to guards is established as necessary by the using service. Such systems should consist essentially of a series of bowl-refractor luminaries or fresnel-lens luminaries, except that fresnel-lens luminaries should always be utilized at Air Force bases for protective boundary lighting. Luminaries should be mounted on poles or buildings located in lines parallel with the boundary lines. Uniform spacing of units, wherever possible, should be maintained throughout the installation. Where required, supplementary lighting units should be used to light entrances and all vulnerable boundary points. Patrol roads and points of observation should be kept in the darkness as much as possible. 
a. 
Protection against intrusion. At locations where lighting is used to discourage the entry of intruders, protective lighting systems should be located approximately 15 to 20 feet from the fence within the bounded area, between the patrol road and the boundary. This distance may be decreased to a minimum of 5 feet when space for patrol road is limited. Luminaires should be arranged to direct the light toward the boundary or area from which the intruder would approach. 

b. 
Protection against escape. At locations where lighting is used' to discourage the escape of prisoners, protective lighting systems should be located 10 to 20 feet from fence beyond the compound area boundary, between the patrol road and this boundary, and arranged to direct the light toward the compound area. Where multiple fences are provided, the outside fence should be considered the boundary fence. 

c. 
Guard towers. Lighting units should be arranged so that glare will not interfere with vision from the guard towers. For this purpose guard towers should be at least 10 feet above the elevation of the luminaires. Each guard tower should be equipped with at least one 12-volt searchlight to be used during emergency periods. At critical points, such as corner guard towers, an emergency storage battery and automatic throwover switch should be provided to insure an uninterrupted supply cf electricity to the searchlight in the event of the failure of normal supply during an emergency. Batteries will not be required at intermediate guard towers, provided the distance between the corner towers does not exceed 2,000 feet and the vision of the guards from these points is not obstructed. 

d. 
Airfields. At airfields, the requirements of Air Force Regulations 86-1, 86-3 and 86-5, prescribing specific horizontal and vertical clearances which must be maintained with respect to aircraft movement areas, are mandatory. Deviations in these criteria will not be made except where unusual terrain conditions prevail and then only when specific authority has been obtained from Headquarters USAF. Protective lighting systems should be designed with the thought in mind of providing the necessary illumination without creating a flight hazard due to the presence of dangerous and extraneous lights near the movement and approach areas of the airfield. Air Force Regulation 91-4 provides that "care must be exercised to prevent the floodlighting or floodlight equipment from interfering with or creating a hazardous condition to ground and aerial traffic." Hence, the design of protective lighting systems at airfields should be closely coordinated with the Flying Safety Officer so that all precautions are exercised to preclude any additional hazard to flying activity. For example, protective lighting which runs parallel to runway lighting and is spaced at approximatey the same intervals could be confusing to pilots and might result in numerous accidents. In designing a protective lighting system for an airfield, full weight should be given to safety in ,aircraft operations as opposed to providing the ultimate in security construction. 


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E. M. PART VI 
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May 1953 
1-47 WIRING SYSTEM. Wiring systems should be selected in accordance with the requirements of paragraph 1-24 or 1-34, as applicable. 
1-48 PROTECTIVE LIGHTING UNITS. The lighting units commonly used for protective lighting are bowl refractor luminaires, fresnel-lens luminaires, flood lights and searchlights. Recommended applications, spacings and lamp sizes are shown in table X. 
a. Bowl refractor luminaires. Bowl refractor luminaires offer an effective means of protective boundary lighting. They should not be used for this purpose however, at Air Force Bases. They may be used for protective area lighting at Air Force Bases. These luminaires may be classified in two general classes as follows: 
(1) 
Class I. Luminaires producing two highly controlled beams of light at exactly 180° apart, characterized by a narrow beam width and carefully graduated high candlepower values in the range of 7° to 30° below horizontal but with little horizontal candlepower. By tilting the unit in the direction away from the pole good shading of sidewise light is effected. Mounting height should be between 25 feet and 30 feet, depending upon the spacing. 

(2) 
Class II. Luminaires producing two strong beams of light approximately 160° apart, characterized by high candlepower values in the range of 7° to 30° below horizontal but with little horizontal candlepower. ·shading of sidewise light on the pole side is also attained. Mounting height should be between 25 feet and 30 feet, depending upon the spacing. 

b. 
Fresnel lens luminaires. These luminaires should be used for protective boundary lighting systems at Air Force installations. Otherwise they should be used only for lighting of boundaries where the terrain is smooth, flat and cleared of obstructions for at least 150 feet outside the boundary limits. Because of the glare produced by these luminaires, their use where roadways or railroads border the boundary line should be avoided. Beam spread of the luminaires is approximately 165° in the horizontal plane and 15° in the vertical plane. Mounting height of units should be between 12 feet and 25 feet. 


Table X. Boundary Lighting 
Bowl refractor luminaires Fresnel-lens luminaires 
Class I Class 2 Spacing LampSpacing I Lamp Spacing I Lamp 
(a) Preferably (a) Preferably (a) Preferably 
150 feet_ ____ ,300 watt or 6,000 lumen 150 feet _____ ,300 watt or 6,000 lumen 125 feet_____ ,300 watt or 6,000 lumen 
Alternate Alternate Alternate 
185 feet_____ ,500 watt or 1,000 lumen 170 feet_ ____ ,500 watt or 10,000 lumen 175 feet_____ ,500 watt or 10,000 lumen 
(b) Preferably (b) Preferably (b) Preferably 
225 feet_ ____ ,300 watt or 6,000 lumen 175 feet _____ ,300 watt or 6,000 lumen 175 feet_____ ,300 watt or 6,000 lumen 
Alternate Alternate Alternate 
300 feet_____ ,500 watt or 10,000 lumen 200 feet _____ ,500 watt or 10,000 lumen 200 feet _____ ,500 watt or 10,000 lumen 
(a). High intensity for highly critical areas such as munitions manufacturing plants and internment camps, 
(b). Medium intensity for less critical areas. 
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E. M. PART VI CHAPTER 1 May 1953 
c. 
Floodlights. Flooulights should be used only for supplementary lighting where a higher intensity of illumination than that provided by luminaires may be required, or for protected area lighting. 

d. 
Searchlights. Searchlights should be used as a form of supplementary lighting where a manually controlled beam is required, such as on guard towers. Spacing of units should be governed by the coverage desired. A one million beam candlepower searchlight has an effective range of approximately 1,000 feet. 


DESIGN ANALYSIS 
1-49 GENERAL REQUIREMENT. Design analyses will be prepared to accompany all plans and specifications for electric power supply, generating plants, electrical distribution systems, street lighting systems, floodlighting systems and protective lighting systems. 
1-50 SCOPE. Design analyses should include information relative to the adequacy, dependability, number, charac~eristics and regulation of incoming supply lines, power company's recommendation relative to the interrupting capacity of main fttses or circuit breakers, total connected load, and estimated maximum demand. Design criteria should 
include computations for transformer capacities, interrupting capacity of substation secondary breakers, voltage drop on primary and secondary feeders, size of emergency generator units and lighting intensities and fixture types for street, area, and protective lighting systems, as applicable. 
1t U. S. GOVERNMENT PRINTING OFFICE : 1962 0 -666906 
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(J'O 868 • 686