Air Compressor Circuit breaker to disconnect wire size

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session88

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Installing a new 15HP 208 VAC 3-Phase Air Compressor.
Nameplate Amps: 42.7
Comp. has factory starter with O.L.'s.

Wire Size from local fused disconnect to compressor:
Per T. 430.250 wire size:
46.2 A x 125% = 57.75 Amps
So I would need #6 AWG XHHW. I will be installing XHHW wire.

Fuse Sizing:
Per T. 430.52 for Squirrel Cage Design B. I can size my local disconnect fuses at 175% of FLC for Dual Element Time Delay Fuses
46.2 x 175% = 80.8 Amp Time Delay Fuses. So 80A or 90A max. Fuses.

Breaker Sizing:
46.2 x 250% for Inverse Time Breaker feeding local fused disconnect = 115.5 Amp Breaker.
So if I install a 115 to 125 Amp (whatever I can purchase nearest to 115 Amps) circuit breaker How do I size the wire between the Breaker and the Local Fused Disconnect ?

Does the wire between the breaker and fused disco. need to be sized according to breaker size ?
Or does my interpretation of T 430.250 above also apply requiring me to run #6 AWG between the Breaker and Local Fused Disconnect ?
 
You would size the conductors at 125% of the amp value in table 430.250 not the nameplate. The OCPD can be larger than the size of the motor conductor.
 
Been debated here previously.. major feel the #6 is ok between the breaker and disconnect.
 
augie47 said:
Been debated here previously.. major feel the #6 is ok between the breaker and disconnect.
Click to expand...
If you have a feeder serving a single motor load, and then a branch circuit serving it, doesn't Article 430 specify the same minimum wire size in both cases? In which case I don't see what there is to debate.

Cheers, Wayne
 
Nor do I, but there are folks who don't look at things thru our eyes and think the feeder to the disconnect has to be sized by the breaker,
I simply wanted the OP to understand there are two schools of thought in case.
 
Thanks for everyone's the help on this. From the get go I was 99% sure Table 430.250 also applies to this wire sizing but wanted to verify.
I will install #6 AWG from breaker to disco. and from disco. to comp.
Thanks.
 
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