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NEC Questions 10/17/2003
By Mike Holt, for EC&M Magazine

Q1. Is it permissible to wrap a stranded wire around the screw terminal of a receptacle?

A1. According to the UL White Book under the RTRT category, stranded wire is permitted to terminate to a screw terminal of a receptacle [110.3(B)].

Q2. Is it permissible to use a galvanized ground rod for a grounding electrode? If yes, is required to be listing?

A2. A galvanized ground of 8 ft in length and not less than 5/8 in. in diameter is permitted to be used as an electrode and no, the rod is not required to be listed [250.52(A)(5)(a)].

Q3. If I installed a listed GE breaker in a listed Square D panel, does this void the panel listing?

A3. Depends on whom you ask. I'm sure equipment manufactures only warrantee their panelboard when used with their circuit breakers. However, UL certifies circuit breakers by independent manufactures to be suitable to be installed in different manufacture panelboards. This is an issue that equipment manufactures constantly battle and it will get resolved by the AHJ [90.4 and 110.3(B)] or by a judge in the courtroom.

Q4. Our township requires a sprinkler system in the electrical equipment room. The sprinkler system is located two feet in front of and just above our main switchboard for the building. There are several sprinklers located along this run and no protection is provided to the switchboard in case of a leak or a sprinkler goes off. Is this a violation of the NEC?

A4. No. Section 110.26(F)(1)(c) (c) permits sprinkler protection of electrical equipment as long as the piping is not located above the switchboard.

Q5. I have a situation were our electrical engineer has designed something I believe may not be code compliant. He wants to supply three separate single-phase 480V transformers (2 phases) from a three-phase breaker. The first transformer is connected to Line 1 and Line 2, the second to Line 2 and Line 3, and the third Line 1 and Line 3. The overcurrent protection device for each of the transformers is sized in accordance with Table 450.3(B). But, is it Code compliant to supply single-phase loads from a three-phase breaker?

A5. Sure. You could use a three-phase breaker to supply three single-phase line-to-neutral loads.

Q6. Can a 277V circuit be used to supplying a wall mounted compact fluorescent night light in a homeless shelter?

A7. Maybe, maybe not. According to 210.6(A) the maximum nominal voltage shall not exceed 120V between conductor for luminaires in dwelling units and guest rooms of hotels, motels, and similar occupancies. Because a room of a homeless shelter would be considered a "similar occupancy", the maximum nominal circuit voltage for luminaires would be 120V. However, this only applies to the guest rooms of the homeless shelter, not the common area.

Q7. Can I plug a power-strip into another power-strip (daisy-chain)?

A7. No, according to the UL White Book (category XBYS), "Relocatable power taps are not intended to be series connected (daisy chained) to other relocatable power taps or to extension cords.

Q8. Could you please tell me if Type NM cable within 7ft from the ground is required to be protected? Example: A wall switch on an open stud wall in the garage. Does the cable coming down the stud from the light have to be sleeved because it is within 7 ft. from the floor?

A8. This is a judgment call by the AHJ. Section 334.15(B) states that NM cable shall be protected from physical damage by conduit, EMT, guard strips, listed surface metal or nonmetallic raceway, or other means.

Q9. Are the receptacles located in a typical treatment room at a doctor's office required to be hospital grade? From my research, if a patient is on a bed, table, or whatever and is being touched, connected to an electrical instrument, a hospital grade receptacle must be used.

A9. No. Hospital grade receptacles are only required for an inpatient "sleeping" bed location; or the bed or procedure table used in a critical patient care area [517.18(B)].

Q10. Can I install a reducing fitting at an explosionproof seal that is located just outside the boundary of a Class 1 Division I area?

A10. Yes, if it's a listed explosionproof reducer fitting. However, if the reducer is located after the seal, then the reducing fitting is not required to be explosionproof listed [501.5(A)(4)].

Q11. Can a 30-kVA transformer be suspended above a suspended ceiling? The ceiling is totally accessible by removing any 2'X 4' ceiling tile and the clearances around and above the transformer comply with code and manufacturer specifications.

A11. Yep, this is fine, just as long as it's a dry-type transformers 600 volts, nominal, or less and not exceeding 50 kVA [540.13(B)].

Copyright 2002 Mike Holt Enterprises,Inc.