A contracting firm I work for is bent out of shape over the new revised Section 210.4(B) and (D) in the National Electrical Code (NEC). The firm, plainly speaking, said this was going to require time to police the trimming out of a panelboard. Members of the firm noted that they use multiwire circuits, which include a neutral that is shared with ungrounded (hot) conductors. Firm members wanted to know exactly what is entailed and if there is a technique that might ease these new requirements.
How does an electrician apply the grouping requirement when trimming out a panelboard? Does an electrician install double or three-pole circuit breakers or maybe use single-pole circuit breakers with handle-ties? Exactly what are the requirements that electrical personnel can use to satisfy these new code rules and ease the impact?
Section 210.4(b) and 210.4(d)
For a better understanding, reviewing the wording of Section 210.4(B) and (D) is in order. First, (B) to Section 210.4 plainly states that each conductor of a multiwire must be disconnected simultaneously at the point where the branch circuit receives its supply. Second, (D) to Section 210.4 states the ungrounded and neutral conductors run with each multiwire circuit must be grouped and identified by tying them together in at least one location or other point of origination. Tie wires or other suitable means may be used to accomplish this purpose. The exception to Section 210.4(D) helps by not requiring such grouping to be applied if the circuit conductors enter from a cable or raceway that is unique to the circuit installation and makes identification obvious by a visual inspection.
Installing multiwire circuits
Electricians must apply good work practices when installing multiwire circuits. For example, if a multiwire circuit contains three ungrounded conductors, electricians can pull these conductors with one neutral through the same raceway, and it is evident and easy to identify this grouping. However, it is not the same installation where six ungrounded conductors, with three and three sharing their own neutral, enter into a panelboard through a raceway, terminating to circuit breakers. Note that two, three-pole circuit breakers or six, single-pole circuit breakers with an individual three-pole handle tie installed on each to provide a simultaneous tripping of the circuits can be used. For safety concerns, each three-wire circuit (multiwire) must be grouped with the appropriate neutral conductor and be identified so as to be recognizable by qualified electrical personnel having authorized access in the panelboard to maintain these circuit breakers and conductors.
Note: Section 210.4(B) and (D) can be bypassed if a neutral is routed with each ungrounded conductor.
Until the NEC implemented this requirement, qualified electricians were trained to know it was a violation of Section 300.13(B), when installing multiwire circuits that shared a common neutral to install the neutral so that its continuity depended on the connections of a device. For the safety of people and equipment, it was and still is a violation for a grounded-neutral conductor to depend on connections of receptacles, lampholders, etc., if removal of such devices and their termination points would interrupt the continuity of the neutral in a multiwire circuit. Be aware and on guard. If the shared neutral is accidentally interrupted by corrosion of connections or removal of devices, voltage and current differences developed in the two or three ungrounded conductors can damage or destroy devices or equipment connected to such lost neutrals.
Another concern for the electrician is a neutral that is not pigtailed with a bonding jumper, if replacement of a device interrupts its continuity and the victim gets between the neutral, a shock can occur. After examination of this section, it is easy to understand that, when these requirements are applied to installations using multiwire circuits, it is safer and the threat of serious damage to devices and equipment that is hardwired or cord-and-plug connected is greatly reduced.
For information purposes, it also is a violation for the equipment-grounding conductor to be interrupted by a receptacle or any other device that breaks its continuation. Section 250.148(B), in effect, requires the arrangement of the grounding connections to be made in a manner that disconnection or the removal of equipment or devices supplied from the box will not interrupt or interfere with the continuity of the grounding scheme. If interruption occurs and a ground fault happens to be present on a permanently or cord-and-plug-connected piece of equipment, electrification is present, and it is dangerous to operate.
Implement these new requirements when installing multiwire circuits and neutrals, and avoid expensive turndowns by the authority having jurisdiction.
STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the NEC and OSHA, as well as other standards. Contact him at 817.581.2206.