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Code Quandaries

May 1, 2008 12:00 PM, By Mike Holt, NEC Consultant

Stumped by the Code?

All questions and answers are based on the 2008 NEC.

Q. What are the requirements for installing isolated ground receptacles?

A. The grounding terminal of an isolated ground receptacle must be connected to an insulated equipment-grounding conductor run with the circuit conductors [250.146(D)], as shown in the Figure. The circuit equipment-grounding conductor is permitted to terminate to the panelboard supplying the power, or it is permitted to pass through the panelboard [408.40 Ex], boxes, wireways, or other enclosures [250.148 Ex] without a connection to the enclosure — as long as it terminates at an equipment-grounding conductor terminal of the derived system or service.

Q. Are you required to pre-twist conductors before installing a twist-on wire connector?

A. Maybe. As per 110.3(B), all electrical products are required to be installed in accordance with equipment instructions. According to the UL “White Book” (product category ZMVV), “some connectors may specify that conductors are to be pre-twisted before assembly onto the connector.”

Q. Can the service disconnecting means for a building be located inside the building?

A. The service disconnecting means must be placed at a readily accessible location either outside the building or structure, or inside nearest the point of service conductor entry [230.70(A)(1)]. Because service-entrance conductors don't have short-circuit or ground-fault protection, they must be limited in length when installed inside a building. Some local jurisdictions have a specific requirement as to the maximum length permitted within a building.

Q. What are the rules for placing overhead service conductors above a swimming pool?

A. Permanently installed pools, storable pools, outdoor spas, outdoor hot tubs, fountains, diving structures, observation stands, towers, or platforms must not be placed within the clearances contained in Table 680.8. This rule doesn't prohibit utility-owned overhead service-drop conductors from being installed over a permanently installed pool, storable pool, outdoor spa, outdoor hot tub, or fountain [90.2(B)(5)]. It does prohibit a permanently installed pool, storable pool, outdoor spa, outdoor hot tub, or fountain from being installed under an existing service drop that isn't at least 22.5 feet above the water.

Q. We have motors that are interlocked, preventing them from being on at the same time. Do we still have to add them up for our service and feeder calculations?

A. No. Where the circuitry is interlocked to prevent operation of motors at the same time, only those motors that operate simultaneously (and result in the largest current) need to be counted [430.24 Ex No. 3].

Q. Where must I install the disconnecting means for a remote building?

A. The disconnecting means for a remote building must be installed at a readily accessible location at the building (outside or inside) nearest the point of entrance of the conductors [225.32].

Q. Am I required to identify the raceways and enclosures in an emergency system?

A. Only the boxes and enclosures (including transfer switches, generators, and power panels) for emergency circuits must be permanently marked as components of an emergency system [700.9(A)]. The Code doesn't require raceways to be identified as a component of an emergency system.

Q. Does the Code allow equipment rooms containing overcurrent devices to be locked? What about locking panel covers and disconnecting means?

A. Yes, electrical equipment rooms and enclosures housing electrical equipment or apparatus can be locked [110.26(G)].

Q. Does the NEC require GFCI protection for a 15A/125V receptacle in a basement for a sump pump?

A. Yes. It is required for all 15A and 20A, 125V receptacles located in the unfinished portion of a basement not intended as a habitable room and limited to storage and work areas [210.8(A)(5)].

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