Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to email@example.com. Answers are based on the 2014 NEC.
GFCI protection of dishwashers in dwelling units
The 2014 NEC has a new requirement for ground-fault circuit interrupter (GFCI) protection of dishwashers in dwelling units. What is the reason for GFCI here? No one is plugging anything in. The equipment grounding conductor should be all that is necessary. If they were going to do this, it should be with the other GFCI requirements for dwelling units. At least I do not have to make the GFCI supplying the dishwasher readily available like all the other requirements.
This is an interesting issue. A new second level subdivision 210.8(D) was added in the 2014 NEC revision cycle. This new requirement did not fit into the current text of 210.8(A), which addresses 125-volt (V), 15- and 20-ampere (A) receptacles because a dishwasher may be hardwired. The new requirement is for GFCI protection of “outlets” that supply dishwashers installed in dwelling-unit locations. As Article 100 states, an outlet is “a point on the wiring system at which current is taken to supply utilization equipment.” Where a dishwasher is hardwired, the point at which the wiring method (e.g., type NM cable) is terminated on the unit is an “outlet.” Therefore, this new rule could not be placed in 210.8(A) with requirements for receptacle outlets. This new GFCI requirement was added because newer electronically controlled dishwashers may have different failure modes than older electromechanical style units. An end-of-life failure of these newer style dishwashers could possibly create a shock hazard, and requiring GFCI protection is prudent to mitigate the potential hazard. While this requirement is in a separate subdivision, the general requirement in the parent text of 210.8 for making the GFCI device protecting the dishwasher “readily accessible” applies. The first printing of the 2014 NEC had an error in 210.8, but errata 70-14-2 corrected the parent text by clarifying that all GFCI devices in “210.8(A) through (D)” be “readily accessible.”
Length of a CEE
On a recent job, we had multiple discussions about how the length of a concrete-encased electrode (CEE) is determined. Is the required 20-foot length to be straight linear feet, or can the conductive ½-inch rebar be bent on angles? For example, we had a 6-foot-by-6-foot square column footing that had a length of rebar around the perimeter (5 + 5 + 5 + 5 = 20 feet). The ½-inch rebar was composed of four 8-foot lengths with a 90-degree bend in the middle. The rebar was tied together with metal tie-wire and tied to the vertical rebar. In a recent Code class we had, all of the drawings for the CEEs were in a straight run. Would the 20 feet of ½-inch rebar run around the base of the footing comply as a CEE?
Yes. Section 250.52(A)(3) permits a CEE made of conductive rebar, not smaller than ½-inch, to be installed in one continuous 20-foot length or in multiple pieces, provided the rebar is connected by the usual steel tie-wires, exothermic welding, welding or other effective means to create a minimum 20-foot length. The example that you provided results in 32 feet of ½-inch rebar installed in a manner that results in a 20-feet length connected by metal tie-wire. This is in compliance with the NEC requirements. There is no requirement stating that the CEE length must be straight or that bends are prohibited.
Transformer secondary conductors and 240.4(B)
The contractor that I work for recently submitted a proposal to install four 150-kilovolt-ampere (kVA) transformers to supply 208/120V in a commercial occupancy expansion. The design submitted had 500 kcmil THHW copper conductors from the transformer secondary to a 400A main circuit breaker in a panelboard. We got the job, but the engineer insisted that the conductors from the transformer secondary be increased to 600 kcmil. The original design was in compliance with 240.21(C)(6). I wanted to question the engineer, but the owner decided to just increase the conductor size and move on. Did we have to increase the size of the conductors?
The engineer was correct in changing the conductor size to 600 kcmil. The requirement that was missed here is in the parent text of 240.21(C). The last sentence states that the provisions of 240.4(B) are not permitted for transformer secondary conductors. The same prohibition exists in 240.21(B) for feeder taps. In this case, the 75°C column ampacity for 500 kcmil copper THHW is 380A. In a general application, 240.4(B) allows you to round up to a 400A overcurrent protective device. The rules for tap conductors in 240.21(B) and (C) do not permit you to do so.
Transfer switches in the critical branch
In the 2014 NEC, specifically Section 517.26, the requirements in Article 700 are applicable only to the life-safety branch, unless modified in Article 517. What happened to applying the requirements in 700 to the critical branch? As an example, Section 517.30(B)(2) requires a transfer switch in each branch of the essential electrical system (life-safety branch, critical branch and equipment branch). Transfer switches used in an emergency system are required to be listed for emergency use as required in 700.5. If the critical branch is no longer required to meet applicable and necessary requirements contained in Article 700, such as the one example provided, can a standard transfer switch be installed? It seems there is a serious reduction in safety requirements here that could compromise the system operation. I believe the product standard for transfer switches used in emergency systems has different and more restrictive requirements than those applicable to standard-use transfer switches. I would appreciate your views on this issue. It seems like it’s an unintended consequence that is not good.
There has been a significant amount of attention in the NEC-revision process with respect to the relationship with NFPA 99, the Health Care Facilities Code, over the last two cycles. Within the NFPA family of codes and standards, many documents interact with each other and clear lines of purview are established. For example, NEC Article 695 provides installation requirements for electric fire pumps. However, the performance of the fire pumps is under the purview of the NFPA 20 committee, and the NEC must follow its lead. The same thing is occurring with healthcare facilities and the NEC. The NFPA Standards Council has clarified that NFPA 99 has purview over performance. This is unlike the relationship between the NEC and NFPA 20. A “healthcare facility” is an occupancy and not a piece of electrical equipment. As you have noted, multiple conflicts are created. There is no longer a requirement for transfer switches in the critical branch to be identified for emergency use. You are correct. The product standard for transfer switches used in emergency systems has different and more restrictive requirements than those applicable to standard use transfer switches. There are more conflicts and unintended consequences including, but not limited to, the fire protection requirements in 700.10(D), which no longer apply to the critical branch.
FMC and luminaires
On a recent job, I observed another electrical contractor installing flexible metal conduit (FMC) from deck-mounted junction boxes for lighting without any means of support. We have always provided at least one piece of nine wire to support the conduit. Does the NEC allow unsupported installation of FMC?
Section 348.30 provides requirements for securing and supporting FMC. The general rule is that FMC must be securely fastened within 12 inches of each termination at a box, cabinet, etc., and it must be supported at intervals not greater than 4½ feet. There are four exceptions to this general rule. Exception No. 4 permits FMC in lengths not exceeding 6 feet from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment. The last sentence in the exception permits (only for the purposes of this exception) listed FMC fittings as a means of support. Where installed in accordance with this exception, the listed FMC fittings are recognized as a means of support.