8/2/2019 5424Ch11[1]

1/8

FM 5-424

Building Attachments and Services 11-1

Part Four. Other Electrical Procedures

CHAPTER 11

Building Attachments and ServicesAll electrical energy supplied to power-consuming devices and appliances

within a bu ilding mu st pa ss th rough th e electr ical service-ent ra nce equipment

where it is metered, protected, and distributed through branch circuits. The

size is determined by the amount of power-consuming devices connected.

Power from militar y generat ors or t he local power compa ny is delivered intoth e building (overhea d or u ndergroun d) thr ough lead-in condu ctors.

SERVICE WIRESThe service wire from the pole to the build-

ing usually consists of two, three, or four

conductors on separate insulators at the

pole and the building or two- or three-con-

ductor, concentric-type service cables. When

installing attachments and services, use

insulated conductors. If installing an over-

head service drop is impractical, run ser-vices underground from a transformer

installation.

LENGTHKeep service drops less than 100 feet long

for No 8, 6, 4, or 2 wire. For No 0 or larger

wire, do not exceed 75-foot spans unless

proper anchoring and support is provided.

Long or large services should be guyed at

th e line pole.

SIZEAlthough No 6 wire is recommended for

overhead service cable, you should deter-

mine th e size by the ma ximum demand load

of electrical equipment used in each build-

ing. Use Table 11-1, page 11-2, to determine

the size of service conductors needed. Since

these calculations do not take motor-start-ing cur rent s into considerat ion, ma ke a sep-

arate check for objectionable flicker. The

number of wires in the service depends on

th e limits given in th e figures an d oth er fac-

tors, such as equipm ent ra ting. For t wo-wire

service, the limit is two circuits in general-

service buildings and four circuits or a 3-

kilowatt connected load in barracks. Three-

wire services ar e required for great er loads.

Use three- or four-wire service to supply

more th an one service switch.

SERVICE ATTACHMENT AT BUILDINGSAttach the service drop to the building

where outlet wires can be tapped in easily

without trailing along the building. Install

the attachment at least 10 feet above the

ground or 18 feet above a roadway. When

the building is not high enough, install a

riser or a pole to obtain proper clearance.

Figure 11-1, page 11-2, shows a correct

open-wire service installation. Figures 11-2

through 11-13, pages 11-3 through 11-6,

8/2/2019 5424Ch11[1]

2/8

FM 5-424

11-2 Building Attachments and Services

show various methods of attaching service

insulators for several types of building con-

struction. Figures 11-14 through 11-16,

pages 11-6 through 11-8, show methods of

at ta ching services to str uctur es.

Table 11-1. Conduc tor type s and sizes

Copper

(AWG or

MCM)

Aluminum or

Copper-Clad

AL (AWG or

MCM)

Ampere

Rating

4 2 100

3 1 110

2 1/0 125

1 2/0 150

1/0 3/0 175

2/0 4/0 200

3/0 250 225

4/0 300 250

250 350 300

350 500 350

400 600 400

Service house attachment Service pole attachment

Figure 11-1. Open-w ire service instal lat ion

8/2/2019 5424Ch11[1]

3/8

FM 5-424

Building Attachments and Services 11-3

Drill a 5/16 hole through sidingonly.

Wood sheathing

Wood siding 2 service insulator

With composition sheathing, use a 4 service insulatorand drill a 1/4 leader hole into the stud or the plate.

Wood sheathing

Brick veneer6 service insulator

Brick veneer

Plate or support Composition sheathing

Stud Stud

Drill aleader hole.

7 1/2 service insulator plateor special support betweenstuds if furnished

7 1/2 service insulator in studwhere no plate or support isprovided

Figu re 11-2. Wood sid ing

Figure 11-3. Brick-ven eer wood sheath ing

Figure 11-4. Brick-venee r comp osit ion sheat hing

8/2/2019 5424Ch11[1]

4/8

FM 5-424

11-4 Building Attachments and Services

9/16 x 2 wood-screw anchor

Drill a 1/2 hole, 2 1/4deep in the brick.

Brick or cement 2 service insulator

Figure 11-5. Solid mas onry, brick or ceme nt

Hollow tile orcement block

Toggle-bolt serviceinsulator

Drill a 7/8hole.

Figure 11-6. Hollow t i le or cemen t block

Service insulator

Drill a 5/16 leaderhole through theshingles only, 1 1/4above the bottomedge of the shingle.

Figure 11-7. Composit ion or

asbestos sh ingles

Stud

Drill a 11/16hole.

5/8 machine bolt

Platewashers

Figure 11-8. Wood, service-conduc tor tension

over 900 pounds

8/2/2019 5424Ch11[1]

5/8

FM 5-424

Building Attachments and Services 11-5

Drill a hole 3 deep with a7/8 drill.

1/2 x 4 machine boltset in 1/2 machine-bolt anchor

Figure 11-9. Solid masonry

Platewasher

5/8 bolt

350 MCM - 500 MCM

Figure 11-10. Attachm en t w ith dead-end spool

Figure 11-11. Service mas t

8/2/2019 5424Ch11[1]

6/8

FM 5-424

11-6 Building Attachments and Services

Feed-through dead end

Figure 11-13. Method of attachin g

mult ip le -conductor serv ices

Service head

Install straps in theopposite direction.

Weatherproofingmaterial

30

30

Sill plate

Ground wire

Ground clamp

Ground rod

Secure to thebuilding with astaple or a strap.

Note: The service cable must beproperly supported.

Figure 11-12. Expos ed service-

entrance cab le

Due to copyright restrict ions ,

this graphic i s un avai lable

ele ctron ically. You m us t

refer to the hard copy

of this product to v iew

this graphic .

Figure 11-14. Entrance he ad below the

roof l ine

8/2/2019 5424Ch11[1]

7/8

FM 5-424

Building Attachments and Services 11-7

Due to copyright restr ict ions , this

graph ic is unav ailable electronical ly.

You mu st refer to the h ard copy

of this produc t to v iew this graphic .

Figure 11-15. Typical un dergroun d servic e

8/2/2019 5424Ch11[1]

8/8

FM 5-424

11-8 Building Attachments and Services

Due to copyright restr ict ions , this

graphic is u na vailable electronic al ly.

You m ust re fer to th e h ard copy

of this product to v iew this graphic .

Figure 11-16. Typical overhead service