rjhavens1
Member
- Location
- Denver Colorado
Thanks for all your help.. Just trying to do it the right way, as you all have showed me, 
wire size for 25a curcuit
- Thread starter rjhavens1
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I am not sure if anyone has made this clear yet so let me add my two cents. The FLA of your compressor is 16.4 amps. 440.32 states that the circuit conductor for a single compressor must have an ampacity of 125% of FLA. 16.4 * 125% = 20.5 amps. The 60 degree ampacity of #12 according to table 310.16 is 25 amps, so the wire is OK. 440.22 allows you to increase the size of the Branch Circuit short circuit and ground fault protection (fuse) to 175% of the FLA of the compressor. 16.4 * 175% = 28.7 amps. So your 25-amp fuse is fine. If the fuse blows before the compressor starts you are allowed to increase the fuse size to 225% of the FLA, which would be 36.9 amps, so a thirty amp fuse would be OK.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Not correct. The manufacturer's Minimum Circuit Ampacity is 16.4 amps, and the Maximum Overcurrent Protective Device rating is 30 amps.haskindm said:
When these numbers are specified, all the math you show is not necessary, and has been figured into these specs.
Larry,
I agree that, with the nameplate information, all of the math is not needed, however the OP said his boss wanted to be shown in the NEC that this installation was acceptable. The steps would demonstrate that the nameplate was in agreement with the NEC.
I agree that, with the nameplate information, all of the math is not needed, however the OP said his boss wanted to be shown in the NEC that this installation was acceptable. The steps would demonstrate that the nameplate was in agreement with the NEC.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
In that case, we have to presume that the 16.4-amp figure includes the 125% mark-up. So, 80% of 16.4 is 13.12, which must be the FLA of the unit. As for the breaker size, 225% of 13.12 is 29.52, which must be where the 30-amp max OC rating comes from.
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