and splicing devices that can be in any space (Articles 312 and 408). The photo below shows an overcrowded disconnect enclosure that does not meet NEC requirements. Even when the conductors between a separate meter and the main disconnect enclosure are accessible, they should not be tapped there unless an enclosure is added to hold the tap device.

In places where net-metering laws are in effect, the utilityside (supply-side) interconnection will be made between the meter and the main service disconnect. In that case, the utility will need to remove the meter from the socket (meter base) to de-energize the service entrance conductors.

If the point of connection is to be the load-side terminals of the meter socket (only when double conductors on these terminals are allowed by the socket listing), extreme caution must be exercised when connecting the new conductors to these terminals. The utility-energized ("hot") input terminals and meter socket jaws are in the same socket and are only a few inches away from each other. Those energized terminals should be covered with a heavy, insulated, protective shield so that they cannot be touched accidentally. Because high

torque is needed to loosen and tighten large terminals, slipping screwdrivers and wrenches are possible. Tools should be insulated, and insulated gloves (lineworker's gloves) and a protective face shield should be worn while working in the meter socket. Touching those "hot" input meter jaws could electrocute you.

The maximum output current from the PV system should be no greater than the rating of the service entrance. Careful consideration should be given to conductor sizes if the PV AC output current approaches the rating of the service entrance. Table 310.15(B)(6) for reduced conductor sizes may no longer apply to a very large PV system. For larger systems, the basic ampacities found in Table 310.16 may have to be used. Since these service-entrance tap conductors have no overcurrent protection, they should be as short as possible and be installed in a metal conduit (RMC, EMT, or IMC). The local jurisdiction may have requirements for protecting the service-entrance conductors that need to be followed for these tap conductors. I do not believe the "tap rules" in Article 240 apply to service-entrance taps since these taps are fully addressed in Article 230.

As for other locations, some existing service-entrance disconnects and meter cabinets have an additional set of terminals that are in parallel with the input connections to the main breaker. These are located to allow the main disconnect enclosure to be easily fed from either the top or bottom of the enclosure.

Some combination meter socket/main disconnect enclosures have the meter socket on one side and the disconnects on the other side of the enclosure. Busbars or cables connect the meter socket to the main breaker. After getting the approval of the enclosure manufacturer and the local inspector, it may be possible to tap these circuits with either bolt-on terminals for the busbars or splicing blocks for the cables. However, normally, busbars may not be drilled and tapped to add terminals for a tap.

Safety for ourselves as installers, for the utility, and for the system owner/operator should be primary considerations. Any work on electrical service-entrance conductors must be done only when those electrical conductors are de-energized. That usually involves notifying the utility and having them turn off all power to the building or structure. Although some electricians will work with "hot" (energized) conductors, this procedure is strongly discouraged. As the old saying goes, "There are old electricians. There are bold electricians. But there are no old, bold electricians."

Was this article helpful?

0 0

Post a comment