October NEC Questions and Answers

[jslatter]

Is there an error in the answer to Q13? It seems to me that the conductor should be #8 AWG according to Table 310.16.

Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75?C.

A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment?s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75?C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

 

[bphgravity]

Re: October NEC Questions and Answers

Mike has already been notified of the error.

 

[pierre]

Re: October NEC Questions and Answers

Remember that Parts III & IV of Art 440 modify the standard requirements of Chapter 3 and permit different ratings for the overcurrent protection and the conductor sizing as per 240.4(G). See 440.22 and 440.32.

Generally the difference is sizing from Art 430 and 440 is that A/C manufacturers have already performed the testing and calcs to size the A/C unit, and we follow the nameplate ratings as provided on the equipment.

[ October 31, 2005, 12:09 PM: Message edited by: pierre ]