Installing Electric
Service-Entrance Systems

[lesson title]

SE Requirements: Attachment of Service Drops

Use back supports in walls that are not strong enough to support a service drop in adverse conditions (wind, snow, or ice) (Figure 1-11). A 2-inch by 4-foot back support gives added strength to the wall.

Figure 1-11. Back support installed in wall.

A single-cable system supports hot conductors and is hooked to the feed-through dead end (Figure 1-12). The cable that supports the service-drop conductors is clamped by the feed-through clamp and coupled to the ground conductors. The cable support is part of the ground system.

Figure 1-12. Grounded messenger cable providing support.

The bare neutral conductor is used as the messenger cable (Figure 1-13). By wrapping the hot conductors around the messenger cable, all the weight of the service drop is on the uninsulated neutral/messenger cable.

Figure 1-13. Hot conductors wapped around a neutral/messenger cable.

In a typical service-drop cable, the neutral conductor is used to attach the cable to the dead end (Figure 1-14). The feed-through clamp is built so that the pull of the conductors makes the clamp tighter on the neutral/messenger cable.

Figure 1-14. Feed-through clamp attached to the service spool.

Service drops are also dead-ended to a building by using secondary racks (Figure 1-15). When heavy service drops are installed on buildings, use secondary racks.

Figure 1-15. Service drop attached to a secondary rack.

When individual conductors are installed, many of the installations are dead-ended by using service spools made of porcelain (Figure 1-16). One service spool is screwed or bolted to the wall.

Figure 1-16. Service drop attached to service spools.

Service masts can dead-end individual conductors and an insulator bracket is used for this purpose (Figure 1-17). An insulator bracket can also be used when service conductors are wrapped around a messenger cable but feed-through clamp will be required.

Figure 1-17. Use of insulator brackets.

Most service masts use a single, dead-end bracket and a service cable (Figure 1-18). This makes a neat installation. Although time-consuming to install, a service mast is the best method for service installation.

Figure 1-18. Insulator bracket with feed-through clamp.

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