Code Alert

Answers to Sep / Oct Live Wire Code Questions:
Courtesy of Mike Holt for EC&M Magazine

Q1. What are the rules for installing boxes in a plenum ceiling?
A1. Only electrical equipment constructed with a metal enclosure is permitted in a space used for environmental air [300.22(C)].

Q2. What are the rules for derating multiconductor cables in a cable tray?
A2. The conductor ampacity adjustment factors of 310.15(B)(2)(a) only apply to the number of current-carrying conductors in the cable and not to the number of conductors in the cable tray [392.11(A)(1)].

Q3. Can I use shared neutrals on an AFCI breaker?
A3. Only if a 2-pole AFCI is used. Single pole AFCI breakers will not operate on a multiwire branch circuit.

Q4. Does a water cooler require GFCI protection?
A4. Electric drinking fountains must be GFCI protected [422.52], but bottled water coolers do not.

Q5. I am told that all receptacles in a dwelling need to be child proof in 2008. Is this true?
A5. Pretty much. The rule is all 15A and 20A, 125V receptacles required in most areas of a dwelling unit [210.52] must be listed as tamper resistant.