Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at email@example.com. Answers are based on the 2020 NEC.
GFCIs in elevator pits
During an inspection of the elevators in a commercial building, the state inspector failed us for using a GFCI-type circuit breaker to protect a receptacle in the elevator pit. He also required GFCI protection for the hard-wired sump pump that did not require it. The resolution was to remove the GFCI circuit breaker and install a GFCI-type receptacle in the pit and add a GFCI circuit breaker for the sump pump. Naturally, we complied immediately so our customer could get a certificate of occupancy. This does not make any sense to us, though. Why would any of that be required?
Section 90.3, Code Arrangement, clarifies that chapters 1 through 4 apply generally and chapters 5, 6 and 7 may supplement or modify requirements in chapters 1 through 7. The requirements of 210.8 for GFCI protection apply to elevators, but are modified in Chapter 6, specifically in Section 620.6. Note that this requirement existed in Section 620.85 in the 2017 NEC . This section requires each 125V, single-phase, 15/20A receptacle installed in pits, hoistways, on the cars of elevators and dumbwaiters associated with wind turbine tower elevators, on the platforms or in the runways and machinery spaces of platform lifts and stairway chairlifts, and in escalator and moving walk wellways to be of the GFCI type.
The reason this requirement mandates GFCI-type receptacles instead of simply “GFCI-protected receptacles” is to provide maintenance personnel with the ability to test and reset the GFCI protection at the point of work. As stated in your question, the inspector required you to remove the GFCI-type circuit breaker.
Section 620.6 does not prohibit upstream GFCI protection, which was not required by the NEC .
However, as written, it is clear that this requirement intends for the ability to test and reset the GFCI protection to exist at each receptacle. It is interesting to note that this section also requires each 125V, single-phase, 15/20A receptacle in machine rooms, control spaces, machinery spaces and control rooms to be GFCI-protected. That could be through a GFCI-type circuit breaker or an upstream GFCI-type receptacle. In the 2017 NEC , 620.85 did not require a single receptacle supplying a permanently installed sump pump to be GFCI protected. However, the 2020 NEC now requires a permanently installed sump pump to be GFCI-protected by an upstream device or by a single receptacle that is GFCI protected.
How many receptacles?
How many receptacles are contained in a duplex receptacle in a single-gang box installed in a dwelling unit? We get conflicting responses.
See the definition of “receptacle” in the 2020 NEC . A new informational note is added following the definition to provide the clarity you seek. The note points out that a duplex receptacle is an example of a multiple receptacle that has two receptacles on the same yoke or strap. However, when we see this question, there are always more layers of the onion we need to peel back to fully understand proper application of the NEC .
It is extremely important to understand the difference between “receptacle” and “receptacle outlet” as used in an NEC requirement. Your question was related to dwelling units. Take a look at two separate requirements: one for receptacles and the other for receptacle outlets. For example, 210.8(A) requires GFCI protection for 125V through 250V receptacles. However, 210.52(A) provides requirements for receptacle outlets. An outlet is defined as a point on the wiring system at which current is taken to supply utilization equipment. Two duplex receptacles in the same box equals four receptacles and one receptacle outlet.
240.4(B) 1,200 amps, why not round up?
On the drawings for a 1,200A feeder in a commercial installation, we designed three 750 kcmil aluminum conductors in parallel, which falls just shy of 1,200A. The plan review identified that as an issue, and the note stated we had to get to 1,200A or higher. We know the rule in 240.4(B) limits rounding up to 800A. A change to three 600-kcmil copper in parallel puts us at 1,260A. In the big picture, what is the difference? We just want to know why.
The reason is heat. This issue has been discussed many times in NEC revision cycles by the committee with purview over Article 240. The reason for limiting the capability to round up to the next larger overcurrent protective device (OCPD) to a ceiling of 800A is heat. Larger OCPDs (over 800A) are tested with full-size conductors under many different environmental conditions at permitted full loads. When current flows, it creates heat, and the larger conductors act as a heat sink to help the OCPD dissipate that heat. The use of smaller conductors could affect the functionality of the OCPD by limiting its ability to dissipate heat.
This issue is obvious in the text of Section 240.91(B) in Part VIII of Article 240, which applies only to supervised industrial installations as defined in 240.2. This permissive requirement provides industrial installations with the ability to round up when over 1,200A, provided the conductor ampacity is equal to or greater than 95% of the OCPD rating and the installation complies with 240.91(B)(1) and (B)(2). Section 240.91(B)(2) requires the OCPD to be listed for this application. That means testing was performed with (smaller) conductors rated at 95% of the OCPD rating, and there were no issues with heat dissipation.
Number of services permitted
In a commercial retail space, there are currently six tenant spaces, each with its own service. This is an older installation with floor-to-ceiling fire walls between each tenant space. We are looking at a project to remove walls to combine three of these tenant spaces into a single space. The designer is using all three existing services to supply power to the new space. Is this permitted? Can we apply one of the exceptions?
No, see Section 230.2. The general requirement in the parent text permits only one service to supply a building or structure. There are provisions permitting additional services in 230.2(A) through (D). A quick look at each one reveals that they do not apply in this installation. Section 230.2(A) permits additional services for special conditions including, but not limited to, supplying a fire pump or emergency system. Section 230.2(B) applies in special occupancies with no space for service equipment or a very large building. Section 230.2(C) applies where the capacity needed is in excess of 2,000A at 1,000V or less or single-phase installations larger than the serving utility can supply. Section 230.2(D) applies only where there is a need for different voltages, frequencies or phases, or for different uses, such as for different rate schedules.
We are supplying a limited amount of overseas equipment at 415/240V in a data center. When complying with 210.5(C), what is the color code for the ungrounded branch circuit conductors?
The NEC does not provide a color code for ungrounded branch circuit (BC) conductors. Grounded conductors, in general, are white or gray, in compliance with 200.6(A). Equipment grounding conductors, in general, are green, as required by 250.119. Any other color can be used for identifying ungrounded BC conductors. In this scenario, it is likely that the premises wiring also has BCs supplied at 480/277V and 208/120V. Section 210.5(C) permits identification by “voltage class.” We can separate these systems into two voltage classes: 150V or less to ground and above 150V to ground. This would allow you to identify the branch circuits supplied at 415/240V in the same manner as BCs supplied at 480/277V.