Article 210                Branch Circuits
Article 240                Overcurrent Protection
Article 250                Grounding and Bonding
Article 314                Outlet, Device, Pull and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures
Article 410                Luminaires (Lighting Fixtures), Lampholders, and Lamps
Article 430                Motors, Motor Circuits, and Controllers
Article 440                Air-Conditioning and Refrigerating Equipment
Article 514                Motor Fuel Dispensing Facilities
Article 517                Health Care Facilities
Article 702                Optional Standby Systems

 

GFCIs for laundry room receptacles

Q:  Does a 15A, 125V receptacle located within 6 feet of a laundry tub, but behind a washing machine in the laundry room of a dwelling unit, have to be GFCI protected? Do the exceptions that do not require GFCI protection for receptacles that supply appliances in dedicated space apply to the receptacle behind the washing machine?

A: The exceptions mentioned in the question only apply to receptacles in garages, accessory buildings and unfinished basements. There is no exception for Item (7) of 210.8(A), which applies to all 15A and 20A, 125V receptacles located within 6 feet of the outside edge of a laundry tub.

Standby generator branch circuits

Q: Is there a requirement in the National Electrical Code (NEC) for optional standby wiring from a generator to be separate from all other wiring?

A: No, there is not. Optional standby systems are covered in Article 702—Optional Standby Systems. It is a short article that occupies a little more than a single page. These systems are generally required to have a transfer switch to prevent back-feed into the utility distribution system. Wiring for optional standby systems may occupy the same raceways, cables, boxes and cabinets with the general wiring in the building. This information is in 702.9.

Wiring gasoline dispensing pumps

Q: Does the NEC permit rigid nonmetallic conduit as the wiring method for gasoline-dispensing pumps? If the answer is yes, are there any special requirements?

A: The answer to the first question is yes. Rigid nonmetallic conduit (RNC) is permitted as a wiring method for gasoline-dispensing pumps under controlled conditions given in Exception No. 2 to 514.8. The conduit must be buried under not less than 2 feet of cover. Where rigid nonmetallic conduit is used, threaded rigid metal conduit or threaded steel intermediate metal conduit must be used for the last 2 feet of underground run up to emergence or to the point of connection to the above-ground raceway. The NEC requires conduit seals as the first fitting above grade except for listed explosion-proof reducers. It does not permit explosion-proof unions, boxes and couplings between the seal fitting and the conduit where it emerges from the earth.

An equipment-grounding conductor is required in the raceway to provide grounding continuity for all non-current-carrying metal parts.

Breakers for switching light circuits

Q: Are all circuit breakers (15A and 20A) suitable for switching lighting branch circuits, or do circuit breakers used for this purpose still require special marking?

A: The requirement for special markings on circuit breakers does not apply to all circuit breakers that switch luminaires (lighting fixtures) on and off. The rule in 240.83(D) only applies to 120V and 277V fluorescent lighting. Where the branch circuit switches this load, the circuit breaker must be marked “SWD” or “HID.” Where a circuit breaker is used to switch high intensity discharge lighting, it must be marked “HID.” There are no special marking requirements for circuit breakers that are used to switch incandescent lighting.

Installing grounding electrodes

Q: Am I permitted to run the grounding-electrode conductor from the building steel to the metal water pipe and then from the building steel to the service grounded conductor at the service? What kinds of connectors are permitted if this method meets the NEC?

A: Yes, 250.50, 250.52, 250.58 and 250.64 grant permission to run the grounding-electrode conductor from one grounding electrode to the other. To provide a grounding-electrode system, 250.50 requires that all grounding electrodes be bonded together. Article 250.52 recognizes 10 feet or more of buried metal water pipe and the metal frame of a building or structure as grounding electrodes. These two grounding electrodes are considered to be a single grounding electrode where they are effectively bonded together by complying with 250.58. And 250.64(F) permits a grounding-electrode conductor to be run to any convenient grounding electrode available in the grounding-electrode system. Part (F) also requires that the grounding-electrode conductor be sized for the largest grounding-electrode conductor required for any of the grounding electrodes connected to it.

Connections of grounding-electrode conductors to grounding electrodes must conform to the requirements in 250.64(C). This part generally requires that grounding-electrode conductors be installed in one continuous unbroken length, but there are four alternate methods that are recognized. The first alternate method may be used for this installation. It allows irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process.

Operating room GFCI protection

Q: Are GFCI-protected receptacles required in operating rooms in hospitals? We remodeled some operating rooms in an existing hospital and installed GFCI receptacles because these rooms were declared wet locations. Now hospital personnel are complaining that circuit breakers are tripping and would like us to remove the GFCI protection. Do you have any suggestions?

A: I suggest that you tell the operating room staff that they have some defective electrical equipment in the operating room that must be repaired or replaced. I would not remove any GFCI circuit breakers or GFCI receptacles unless they prove to be defective. If any are found to be defective, replace them, but I suspect the problem is with the equipment.

According to Underwriters Laboratories standards, listed appliances must not have leakage current greater than 0.5 milliamps when tested for compliance.

Where electric power interruption cannot be tolerated (as in an operating room), an isolated power system may be provided instead of GFCIs. Requirements for an isolated power system and equipment are located in 517.160.

I mentioned GFCI receptacles to cover all possibilities, even though “hospital grade” receptacles with self-contained GFCIs may not be available.

Disconnect for evaporator fan

Q: Does the NEC require a disconnect switch within sight of an evaporator fan motor? The refrigeration installation personnel do not want a switch for this motor because someone can turn it off and cause a freeze up.

A: Yes. The NEC requires a disconnect for the evaporator fan. However, the disconnect is permitted to control other motor loads. A single disconnecting means is allowed to disconnect the hermetic refrigerant motor-compressor and evaporator fan. This arrangement will prevent disconnecting the evaporator motor by itself. Article 440.12 (B) permits a single disconnect for more than one motor.

A sign at or on the disconnect that reads, “Evaporator Fan—Do Not Turn Off” or similar language should help to prevent anyone from turning this switch off by mistake if it is decided to leave the switch in place.

Motor vehicle hoist motors

Q: Motor vehicle hoist motors, which are part of a UL-listed vehicle, do not have overload protection. Do these assemblies satisfy the requirements in the NEC?

A: If the only concern is the absence of motor-overload protection, the answer is yes. The Note under the Duty-Cycle Service Table 430.22(E) reads that any motor application shall be considered as continuous duty unless the nature of the apparatus it drives is such that the motor will not operate continuously with load under any condition of use. Since these lifts are generally operated by handheld, momentary-contract pendant switches, the motor never operates continuously. Therefore, 430.33 Intermittent and Similar Duty applies. Part of 430.33 reads “A motor used for a condition of service that is inherently short-time, intermittent, periodic, or varying duty as illustrated by Table 430.22(E) shall be permitted to be protected against overload by the branch-circuit, short-circuit and ground-fault protective device, provided the protective device rating or setting does not exceed that specified in Table 430.52.”

It is also necessary to follow the manufacturer’s installation and user instructions to comply with 110.3(B) in the NEC.

Size of service conductors

Q: Can I run three sets of 500Kcmil copper conductors with Type THWN insulation for a 1,200A service?

A: No. A 1,200A overcurrent device cannot protect these service-entrance conductors because their total ampacity is 1,140A (380 × 3), and 240.4(B) does not permit rounding up to the next larger size fuses or circuit breaker because 240.4(B)(3) limits this permission to overcurrent protection rated 800A or less. These service conductors must be protected by a standard size 1,000A overcurrent device or an 1,100A nonstandard size overcurrent device. Conductor size must be increased to 600 Kcmil copper for a 1,200A service.

Conductors needed in outlet boxes

Q: Can round pancake boxes measuring 3.5 inches and 0.5 inch deep be used with 14–2/ground type NM cable to supply luminaires (lighting fixtures)? Can the fixture canopy be considered as providing additional wiring space in the box?

A: Yes. The volume of the canopy may be added to the volume of the box. Article 314.16(A), which allows the volume of a domed cover to be added to the volume of the box, permits this. Also, 410.10 allows canopies and outlet boxes taken together to provide adequate space for connection of luminaire (fixture) conductors and branch-circuit conductors.         EC

FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.