7.) The non-bonding of service raceways and equipment.
Note: This item has been part of the most common deficiencies since 1999. Although this is not found as often as it was prior to 1999, it still is an issue that is misunderstood and therefore bares consideration.
Section 250.92(A) requires the non-current carrying metal parts of service equipment, indicated in Section 250-92(A)(1), (2) and (3), to be effectively bonded together. Section 250.92(A)(1) speaks to service raceways and Section 250.92(A)(2) speaks to all service equipment enclosures containing service conductors, including meter fittings, boxes, and the like interposed in the service raceway. Section 250.92(B) describes the methods that will ensure the electrical continuity of the service equipment. As described in Section 250.92(B) standard locknuts or bushings are not an acceptable means for the bonding required by this section.
Example: a structure that has an overhead service. The service entrance conductors splice to the service drop and run down an EMT raceway to the meter enclosure. The EMT raceway is secured to the hub on top of the meter enclosure with a compression connector. The EMT raceway runs from the back of the meter enclosure directly through the wall and attaches to the service disconnect enclosure with standard connectors, locknuts and plastic bushings on both ends. The problem here is a bonding fitting should have been used on one end of the EMT raceway running from the meter enclosure to the service disconnect enclosure to bond the raceway. The EMT riser is effectively bonded by the threaded hub on the top of the meter enclosure. If there were any wireways or boxes installed in the raceway system they would be required to be bonded as well. Section 250.102(C) requires equipment bonding conductors on the supply side of the service to not be smaller than the sizes shown in Table 250.66.