|By Mike Holt, for EC&M Magazine
Q1. Is it permissible to wrap a stranded wire around the screw terminal of a
A1. According to the UL White Book under the RTRT category,
stranded wire is permitted to terminate to a screw terminal of a receptacle
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
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
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?
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.
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?
Sure. You could use a three-phase breaker to supply three single-phase
Q6. Can a 277V circuit be used to supplying a
wall mounted compact fluorescent night light in a homeless shelter?
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
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
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
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.