Article 110 Requirements for Electrical Installations; Article 210 Branch Circuits; Article 250 Grounding and Bonding; Article 314 Outlet, Device, and Pull and Junction Boxes, Fittings, and Handholes; Article 350 Liquidtight Flexible Metal Conduit: Type LFMC; Article 517 Health Care Facilities; Article 590 Temporary Wiring
GFCIs for air conditioners
Is ground-fault circuit interrupter (GFCI) protection required for an outdoor receptacle that is installed within 25 feet of air conditioners in a multitenant office building?
If the receptacle is installed outdoors, Section 210.8(B)(4) of the National Electrical Code (NEC) requires it to be GFCI--protected. This part (B) applies to all 15- and 20-ampere, 120-volt receptacles.
A receptacle for servicing the air conditioning equipment is required within 25 feet and at the same level as the air conditioning units, and cannot be supplied from the load side of the disconnecting means supplying the equipment.
Multiwire branch circuit for GFCIs
Is it permissible to use two GFCI receptacles supplied by a multiwire (120/240V) branch circuit for the kitchen receptacles? What if two single-pole GFCI circuit breakers are used?
I answered a similar question in a previous issue of ELECTRICAL CONTRACTOR magazine, but some readers told me the answer was incomplete because I did not mention GFCI receptacles in my response. I limited my answer to the use of single-pole GFCI circuit breakers, but my reference to circuit-breakers was not clear.
A multiwire branch circuit will not work with GFCI circuit breakers because an unbalanced current in the neutral (grounded-circuit conductor) will cause the circuit breaker to trip whenever the unbalanced current in the neutral exceeds 6 milliamperes.
GFCI receptacles may be supplied from a multiwire branch circuit, and they will operate as required provided that a two-wire branch circuit is connected to the downstream side of the receptacle. A two-wire branch circuit is required to be connected to the load side of the receptacle, and the grounded branch circuit conductor is not part of the multiwire branch circuit that supplies the receptacles. The multiwire branch circuit must stop at the line terminals of the receptacles, and two-wire branch circuits must be used from the GFCI receptacles to the other receptacles on the branch circuit.
Isolated ground receptacles
Is the isolated equipment-grounding conductor for an isolated ground receptacle required to be connected to boxes, wireways, enclosures, etc., where the isolated equipment--grounding conductor passes through these boxes and enclosures without making a connection to these enclosures? Section 250.146(D) only requires that the isolated--ground conductor not be connected to other panelboards.
A change was made in the 2008 edition to Section 250.146(D) of the NEC that now requires isolation of the isolated equipment-grounding conductor from all-metal enclosures. The revised portion reads, “Where installed in accordance with the provisions of this section, this equipment grounding conductor shall also be permitted to pass through boxes, wireways, or other enclosures without being connected to such enclosures.”
Temporary wiring using Type NM cable
Is it permissible to run nonmetallic sheathed cable (Type NM) exposed in a Type IV building that is under construction?
Although Item 3 of 334.10 prohibits NM cables from being exposed in Types III, IV and V construction, there is permission to conceal cables within walls, floors or ceilings. These cables must be concealed within walls, floors or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating. But this requirement applies to the permanent wiring of the building.
Temporary wiring is covered by Article 590—Temporary Wiring, and part of 590.4(C) states: “Conductors shall be protected from overcurrent as provided in 240.4, 240.5, and 240.11. For the purpose of this section, Type NM and Type NMC cables shall be permitted to be used in any dwelling, building, or structure without any height limitation or limitation by building construction type and without concealment within walls, floors, or ceilings.” Section 590.3(D) requires immediate removal of temporary wiring upon completion of construction.
Grounding-electrode conductor required
I am installing three 8 AWG copper feeder conductors in a metal raceway from a residence to a garage. Is it necessary to provide a grounding electrode and grounding-electrode conductor at the garage?
Yes, it is. See Section 250.32. Where the 8 AWG conductors are feeders to the garage, it is necessary to provide a grounding-electrode system. Although the metal raceway provides an equipment--grounding conductor, a grounding-electrode system is required. Part (B) contains additional information that reads, “The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrodes.” There are some exceptions to this part (B), but I do not think they apply to this question.
Location of panelboard
Does the Code permit the installation of a panelboard in the manager’s locked office in a commercial building?
Yes, a panelboard may be installed in an office that has a locked door. According to article 110.26(B), “Locked Electrical Equipment Rooms or Enclosures. Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to qualified persons.” Space around the panelboard must comply with 110.26, which requires sufficient access and working space to the panelboard so that ready and safe operation of the equipment can be serviced and maintained.
Wiring for patient care areas
Does the wall switch for a luminaire in a patient care room of a hospital require a redundant ground? The switch is less than 7.5 feet above the floor.
Yes, the metal raceway system or metal-sheathed cable must provide an equipment-grounding conductor that qualifies for grounding in accordance with 250.110. Listed Type AC (armored cable) qualifies as an equipment ground because a bond wire under and in contact with the armor for its entire length is recognized as a grounding conductor. An insulated equipment-ground wire in the cable assembly meets the requirement for redundant grounding as required by 517.13. Some corrugated metal strip armor Type MC cable also qualifies where the equipment-grounding conductor/bond wire is not included in the wrapping of the branch-circuit conductors. With the bare bonding conductor in contact with the underside of the armor, the armor is an effective ground path, and this product, with an insulated equipment-grounding conductor, qualifies the armor as a grounding conductor.
Although there is no requirement in the NEC in Articles 320 and 330 for these cables to be listed, I would use only listed cables for this application.
Supporting junction boxes
Is a 4-inch square junction box secured with two 0.5-inch rigid metal conduits, one on each side, and a 0.75-inch metal conduit that enters in the back? All conduits are secured to the box with locknuts and bushings, and the box only contains splices.
Methods of securing enclosures are covered by 314.23(A) through (H). Part (E) of this section reads: “(E) Raceway Supported Enclosures, Without Devices Luminaires or Lampholders. An enclosure that does not contain a device(s) other than splicing devices or support a luminaire(s), lampholder(s), or other equipment and is supported by entering raceways shall not exceed 1,650 cm3 (100 in3) in size. It shall have threaded entries or have hubs identified for the purpose. It shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. Each conduit shall be secured within 900 mm (3 ft.) of the enclosure or within 450 mm (18 in.) of the enclosure if all conduit entries are on the same side.”
Locknuts and bushings are not recognized as a means for supporting a junction box.
Supporting liquidtight FMC
Am I required to secure 6 feet of liquidtight flexible metal conduit (LFMC) that is -installed outdoors from a disconnect to an air conditioning unit?
LFMC must be fastened securely within 12 inches of the disconnect and 12 inches of the air conditioner terminal box. No intermediate supports are required if the supports are placed so that the unsupported length does not exceed 4.5 feet.
Part 350.30(H) requires that LFMC be fastened securely in place by an approved means within one foot of each box, cabinet, conduit body or other conduit termination and be supported and secured at intervals of 4.5 feet or less. Where the conduit is secured one foot from the end of the conduit, no intermediate support is required.
The only exception that might apply is Exception No. 2 where flexibility is required after installation. This exception is divided into three parts, and the distance between securing the LFMC is based on the size of the conduit.
LFMC exposed to the weather is considered to be in a wet location. Section 300.9 is new in the 2008 edition of the NEC and makes it clear that conduits installed outdoors exposed to the weather are in a wet location, and enclosed conductors must be suitable for wet locations.
A list of conductor insulation types is included in 310.8(C). This list includes 12 different insulation types.
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. Questions can be sent to firstname.lastname@example.org.