All questions and answers are based on the 2005 NEC.
Q. I have six 18-foot metal poles to install in a parking area. Is a ground rod required at each pole? If not, then why do some people insist that they are required?
A. No. The grounding of a metal pole is not required by the NEC. However, to protect against electric shock from a ground fault, dangerous voltages on metal parts must be removed by opening the circuit's overcurrent protection device. To quickly remove dangerous touch voltage on metal parts from a ground fault, the fault current path must have sufficiently low impedance to allow the fault current to quickly rise to a level that will open the branch-circuit overcurrent protection device [250.2 and 250.4(A)(4) and (5)]. As shown in the Figure, this is accomplished by the bonding of metal parts to an effective ground-fault current path with an equipment grounding (bonding) conductor of a type specified in 250.118.
Q. Is there a Code rule that prohibits nonelectrical equipment in an electrical room?
A. No, there is no such Code rule. However, 110.26(F) prohibits nonelectrical equipment above and below switchboards, panelboards, distribution boards, and motor control centers. In addition, the minimum working space of 30 by 36 inches must also be kept clear at all times, and cannot be used for storage [110.26(B)].
Q. Is plenum-rated cable required in an equipment room, if the room is used as a return air space, via a grille on the equipment room door?
A. The requirements for wiring in air handling spaces do not apply to rooms whose prime purpose isn't air handling [300.22(C)], so plenum-rated cabling would not be required.
Q. How far away from the electric service must I locate a hot tub?
A. Circuit breakers, time clocks, pool light switches, and other switching devices must be located not less than 5 feet horizontally from the inside walls of a permanently installed outdoor hot tub unless separated by a solid fence, wall, or other permanent barrier [680.22(C)].
Q. I ran 14/3 NM cable to the bedroom outlets, and my boss says you can't put an AFCI breaker on a multi-wire branch circuit. Is this true?
A. Your boss is almost right. Two single-pole AFCI breakers cannot be used on a 3-wire circuit; however a 2-pole AFCI breaker can be used for this purpose.
Q. Can energized power conductors be abandoned in place? If not, must I remove the conductors from the circuit protection device, or must I remove the conductors completely?
A. Abandoned power and lighting conductors are not required to be removed, but the free ends of all conductors must be covered with insulation that is equal to that of the conductor [110.14(B)]. However, keep in mind that the accessible portions of all audio, limited energy, signaling, fire alarm optical fiber, and communications cables are required to be removed [640.3(A), 725.3(B), 760.760.3(A), 770.3(A), 800.3(C), 820.3(A) and 830.3(A)].
Q. Can pneumatic control tubing be installed in the same raceway with electrical control or power conductors or cables?
A. Raceways and cable trays are designed for the exclusive use of electrical conductors and cables, and cannot contain nonelectrical components, such as pipes or tubes for steam, water, air, gas, drainage, etc. [300.8].
The limitations of 300.8 do not apply to Class 2 and Class 3 circuits using Class 2 and Class 3 wiring methods [725.3 and 725.52(B)], but they do apply to Class 1 circuits [725.25] and Class 2 and Class 3 circuits utilizing Class 1 wiring methods [725.52(A)].
Q. What are the grounding requirements for a trailer that receives power via a portable generator that happens to be mounted on the frame of the trailer?
A. The frame of a portable generator isn't required to be grounded to the earth if the generator only supplies equipment or receptacles mounted on the generator, and the metal parts of the generator and the receptacle grounding terminal are bonded to the generator frame [250.34(A)].
Note: In this case, the trailer is not required to be grounded to the earth either.
Q. I have to move an outdoor post light and was wondering if I could splice the UF cable underground without a junction box?
A. Direct-buried conductors or cables can be spliced underground without a splice box [300.15(G)], if the splice or tap is listed for the purpose [300.5(E), 110.14(B)].
Q. I thought that the Code had a limit of one wire per terminal, but some say that it's okay to terminate two wires on some circuit breakers? Is this true?
A. Maybe. Terminals for more than one wire must be identified for this purpose — either within the equipment instructions or on the terminal itself [110.14(A)]. Some equipment contains terminals that are listed for more than one conductor per terminal. For example, at least two manufacturers' circuit breakers rated 30A or less are permitted to have two conductors under each lug.