NEC Questions and Answers – based on the 2008 NEC
August 2010
By Mike Holt for EC&M Magazine
Here’s the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent, so you can see how you did.
Q1 Can conductors be spliced inside a raceway?
A1 No. Conductors in raceways must be continuous between all points of the system, which means splices must not be made in raceways, except as permitted for non-circular raceways such as wireways by 376.56, 378.56, 384.56, 386.56, or 388.56. [300.13(A)].
Q2 Is overcurrent protection required for a panelboard?
A2 Each panelboard must be provided with overcurrent protection located within or at any point on the supply side of the panelboard. The overcurrent device must have a rating not greater than that of the panelboard, and it can be located within, or on the supply side, of the panelboard [408.36].
Exception No. 1: Individual overcurrent protection is not required for panelboards used as service equipment in accordance with 230.71.
When a panelboard is supplied from a transformer, as permitted in 240.21(C), the overcurrent protection for the panelboard must be on the secondary side of the transformer. The required overcurrent protection can be in a separate enclosure ahead of the panelboard, or it can be in the panelboard [408.36(B)].
Q3 Am I required to ground metal cover plates on receptacles and switches?
A3 Yes, metal faceplates for receptacles and switches must be grounded.
Section 406.5(B) requires that metal faceplates for receptacles must be connected to the circuit equipment grounding conductor.
The NEC doesn’t specify how this is accomplished, but 517.13(B) Ex 1 for health care facilities permits the metal mounting screw(s) securing the faceplate to a metal outlet box or wiring device to be suitable for this purpose.
For switches, dimmers, and similar control switches, the metal mounting yokes must be connected to an equipment grounding conductor of a type recognized in 250.118, whether or not a metal faceplate is installed. The metal mounting yoke is considered part of the effective ground-fault current path by one of the following means:
(1) Mounting Screw. The switch is mounted with metal screws to a metal box or a metal cover connected to an equipment grounding conductor of a type recognized in 250.118. [404.9(B)]
Author’s Comment: Direct metal-to-metal contact between the device yoke of a switch and the box isn’t required.
(2) Equipment Bonding Conductor. An equipment grounding conductor, or equipment bonding jumper is connected to the grounding terminal of the metal mounting yoke.
Exception: The metal mounting yoke of a replacement switch isn’t required to be connected to an equipment grounding conductor of a type recognized in 250.118 if the wiring to the existing switch doesn’t contain an equipment grounding conductor and the switch faceplate is nonmetallic or the replacement switch is GFCI protected.
Q4 Please explain the grounding requirements for receptacles and equipment in patient care area of health care facilities.
A4 Wiring in patient care areas must comply with (A) and (B) of 517.13:
(A) Wiring Methods. All branch circuits serving patient care areas must be provided with an effective ground-fault current path by installing circuits that serve patient care areas in a metal raceway or cable having a metallic armor or sheath that qualifies as an equipment grounding conductor in accordance with 250.118 [517.13].
Author’s Comments:
- The metal outer sheath of AC cable is listed as an equipment grounding conductor because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)].
- The metal outer sheath of interlocked Type MC cable is not listed as an equipment grounding conductor unless it contains a bare aluminum conductor that makes direct contact with the metal sheath of the cable [250.118(10)(a)].
(B) Insulated Equipment Grounding Conductor. In patient care areas, the grounding terminals of receptacles and conductive surfaces of fixed electrical equipment must be connected to an insulated copper equipment grounding conductor. The circuit equipment grounding conductor must be sized in accordance with 250.122 and the wiring method must meet the requirements of 517.13(A).
Exception No. 1: Metal faceplates for switches and receptacles can be connected to the equipment grounding conductor by the metal mounting screws that secure the faceplate to a metal outlet box or metal mounting yoke of switches [404.9(B)] and receptacles [406.3(C)].
Exception No. 2: Luminaires located more than 7½ ft above the floor can be connected to the equipment grounding return path complying with 517.13(A), without being connected to an insulated equipment grounding conductor.
Q5 How many neutral wires can I install on a singe terminal in a panelboard?
A5 Each neutral conductor within a panelboard must terminate to an individual terminal according to 408.41.
Author’s Comment: If two neutral conductors are connected to the same terminal, and someone removes one of them, the other neutral conductor might unintentionally be removed as well. If that happens to the neutral conductor of a multiwire circuit, it can result in excessive line-to-neutral voltage for one of the circuits, as well as undervoltage for the other circuit.. See 300.13(B) for details.
This requirement doesn’t apply to equipment grounding conductors because the voltage of a circuit is not affected if an equipment grounding conductor is accidentally removed.
Q6 What are the GFCI requirements for a non-dwelling units?
A6 GFCI protection is required for all 15A and 20A, 125V receptacles installed in the following commercial/industrial locations [210.8(B)]:
(1) Bathrooms. All 15A and 20A, 125V receptacles installed in commercial or industrial bathrooms must be GFCI protected.
Author’s Comments:
- See the definition of a “Bathroom” in Article 100.
- A 15A or 20A, 125V receptacle isn’t required in a commercial or industrial bathroom, but if one is installed, it must be GFCI-protected.
(2) Kitchens. All 15A and 20A, 125V receptacles installed in an area with a sink and permanent facilities for food preparation and cooking [Article 100], even those that don't supply the countertop surface, must be GFCI-protected.
Author’s Comments:
- GFCI protection is not required for receptacles rated other than 15A and 20A, 125V in these locations.
- GFCI protection is not required for hard-wired equipment in these locations.
(3) Rooftops. All 15A and 20A, 125V receptacles installed on rooftops must be GFCI-protected.
Author’s Comment: A 15A or 20A, 125V receptacle outlet must be installed within 25 ft of heating, air-conditioning, and refrigeration equipment [210.63].
(4) Outdoors. All 15A and 20A, 125V receptacles installed outdoors must be GFCI-protected.
Exception No. 1 to (3) and (4): GFCI protection isn’t required for a fixed electric snow-melting or deicing equipment receptacle supplied by a dedicated branch circuit, if the receptacle isn’t readily accessible and the equipment or receptacle has ground-fault protection of equipment (GFPE) [426.28].
(5) Sinks. All 15A and 20A, 125V receptacles installed within 6 ft of the outside edge of a sink must be GFCI-protected.
Q7 What are the supporting and securing requirements for Type MC cable?
A7 Section 330.30 lists these rules for securing and supporting Type MC cable:
(A) Type MC cable must be supported and secured by staples, cable ties, straps, hangers, or similar fittings, designed and installed so as not to damage the cable.
(B) Type MC cable with four or less conductors sized no larger than 10 AWG, must be secured within 12 in. of every outlet box, junction box, cabinet, or fitting and at intervals not exceeding 6 ft.
(C) Type MC cable must be supported at intervals not exceeding 6 ft. Cables installed horizontally through wooden or metal framing members are considered secured and supported where such support doesn’t exceed 6 ft intervals.
(D) Unsupported Cables. Type MC cable can be unsupported where the cable is:
(1) Fished through concealed spaces in finished buildings or structures, where support is impracticable, or
(2) Not more than 6 ft long from the last point of cable support to the point of connection to luminaires or other electrical equipment within an accessible ceiling. Type MC cable fittings are permitted as a means of cable support.
Q8 Can I install a panelboard in a bathroom or closet?
A8 Overcurrent devices must not be located near easily ignitible material, such as in clothes closets [240.24 (D)].
Author’s Comment: The purpose of keeping overcurrent devices away from easily ignitible material is to prevent fires, not to keep them out of clothes closets.
Overcurrent devices must not be located in the bathrooms of dwelling units, or guest rooms or guest suites of hotels or motels [240.24 (E)].
Author’s Comment: The service disconnecting means must not be located in a bathroom, even in commercial or industrial facilities [230.70(A)(2)].
Q9 What is the maximum number of bends in a circular raceway?
A9. This answer is found in each individual raceway article, where the maximum number of degrees between pull points is limited to 360 degrees for non-flexible circular raceways. For example, 344.26 deals with rigid metal conduit, and says:
To reduce the stress and friction on conductor insulation, the maximum number of bends (including offsets) between pull points cannot exceed 360°.
The same rule for other circular raceways are: IMC 342.22, FMC 348.26, PVC 352.26, HDPE 353.26, NUCC 354.26, RTRC 355.26, EMT 358.26, ENT 362.26
Author’s Comment: There is no maximum distance between pull boxes because this is a design issue, not a safety issue.
Q10 What are the GFCI protection requirements for vending machines?
A10 Cord-and-plug-connected vending machines must include a GFCI as an integral part of the attachment plug, or within 12 in. of the attachment plug. Older machines that are not so equipped must be connected to a GFCI-protected outlet [422.51].
The term “vending machine” means a self-service device that dispenses products or merchandise and requires coin, paper currency, token, card, key, or receipt of payment by other means.
Author’s Comment: Because electric vending machines are often located in damp or wet locations in public places, and are used by people standing on the ground, reliance on an equipment grounding conductor for protection against electrocution is insufficient.
Q11 What is the sizing rule for an equipment grounding conductor in a raceway that contains multiple circuits?
A11 When multiple circuits are installed in the same raceway, cable, or cable tray, only one equipment grounding conductor is required for the multiple circuits, sized in accordance with 250.122, based on the rating of the largest circuit overcurrent device [250.122(C)].
Author’s Comment: Single conductors used as equipment grounding conductors in cable trays must be sized 4 AWG or larger [392.3(B)(1)(c)].
