Stumped by the Code?

Sep 1, 2005 12:00 PM, By Mike Holt, NEC Consultant

All questions and answers are based on the 2005 NEC.

Q. Where are hospital-grade receptacles required?

A. Receptacles for inpatient sleeping beds or procedure table beds used in a critical patient care area (patient bed location) must be listed as “hospital grade” [517.18(B)].

They aren't required in treatment rooms of clinics, medical and dental offices, or outpatient facilities because these facilities don't have a “patient bed location” as defined in 517.2 (Figure at right).

The deciding factor in whether you need hospital grade receptacles is the presence of a patient bed.

Q. Does the Code allow armored cable to terminate in a plastic box?

A. No. Nonmetallic boxes may not be used with a metallic wiring method because there's no way to maintain the electrical continuity of the effective ground-fault current path (250.2 and 314.3). However, Ex. 1 of 314.3 does allow you to use nonmetallic boxes with metal raceways and metal cables if you provide an internal bonding means in the box between all metal entries. Ex. 2 also recognizes the use of nonmetallic boxes with metallic wiring methods if you provide an integral bonding means with a provision for attaching an equipment bonding jumper inside the box between all threaded entries.

Q. I'm running a 4-wire lighting circuit with a shared neutral. Can I use three single-pole breakers without handle ties?

A. Yes. Individual single-pole breakers can be installed on each ungrounded conductor of a multiwire branch circuit that supplies line-to-neutral loads for lighting or receptacle circuits [240.20(B)(1)]. However, multiwire branch circuits that supply switches, receptacles, or equipment on the same yoke must be provided with a means to disconnect simultaneously all ungrounded conductors that supply those devices or equipment at the point where the branch circuit originates [210.4(B) and 210.7(B)]. This can be accomplished by single-pole circuit breakers with handle ties identified for the purpose of a 2- or 3-pole breaker with common internal trip.

Q. Now that the 2005 NEC requires a concrete-encased electrode of the rebar type for the service, is a ground rod still required?

A. No. The only time a concrete-encased electrode of the rebar type isn't required is for existing buildings or structures where the conductive steel reinforcing bars aren't accessible without disturbing the concrete (250.50 Ex.). Therefore, in a new building or structure, you must use a concrete-encased electrode of the rebar type installed in accordance with 250.52(A)(3).

However, in existing buildings or structures, you can use a ground rod (or two) as the required grounding electrode. Just be sure to install it in accordance with 250.52(A)(5). If a single ground rod has a resistance of more than 25 ohms, drive an additional one and bond it to the first ground rod.

Q. Under what condition can a two-wire receptacle be replaced with a three-wire receptacle, when no ground is available in the box?

A. Where no equipment bonding means exists in the outlet box, nongrounding-type receptacles can be replaced with [406.3(D)(3)]:

Another nongrounding-type receptacle.
A GFCI grounding-type receptacle marked “No Equipment Ground.”
A grounding-type receptacle, if GFCI protected and marked “GFCI Protected” and “No Equipment Ground.”

Note: GFCI protection will function properly on a 2-wire circuit without an equipment grounding (bonding) conductor because the equipment grounding (bonding) conductor serves no role in the operation of the GFCI-protection device.

Caution: The permission to replace nongrounding-type receptacles with GFCI-protected grounding-type receptacles doesn't apply to new receptacle outlets that extend from an existing ungrounded outlet box. Once you add a receptacle outlet (branch-circuit extension), the receptacle must be of the grounding (bonding) type and it must have its grounding terminal grounded (bonded) to an effective ground-fault current path in accordance with 250.130(C).

Q. I'm installing a 12A, 240V “wet saw,” and the manufacturer requires the motor to have GFCI protection. I don't believe this motor can be GFCI protected because it doesn't have a neutral. Do we need GFCI protection on this piece of equipment?

A. Yes. GFCI protection is required because equipment must be installed and used in accordance with any instructions included in the listing or labeling requirements. As an aside, remember that a neutral isn't necessary for the proper operation of a two-pole GFCI circuit breaker.

Q. Can Type MC armored cable of the interlocked type be used for the wiring of luminaires in the examining rooms of a doctors office?

A. Nope. All branch circuits that serve patient care areas must be installed in a metal raceway or listed cable with a metallic armor or sheath that qualifies as an effective ground-fault current path in accordance with 250.118 [517.13(A)]. Typically, the outer metal sheath of interlocked Type MC cable isn't listed as a suitable ground-fault current path [250.118(10)]. Therefore, it's not permitted to supply branch circuits in patient care areas of health-care facilities.

Note: The requirement of an additional equipment grounding (bonding) conductor within the wiring method for patient care areas isn't applicable for luminaires located more than 7 feet, 6 inches above the floor [517.13(B) Ex. 2].

Clashing with your local inspector? Need Mike to settle a debate? E-mail him at mike@mikeholt.com for help.