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Compressor Wiring Solutions

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chedore

chedore

GANEX
Location
Quebec, Canada
Occupation
Electromecanical technician, Automation Technician
Hello everyone. I need to change one of our compressors here in our shop and we were looking to buy a used 100HP compressor.
amprating100hp.png
On this image, we see that the Nameplate Amps of a 100HP compressor on 575V is 90.4A, and the Starter Amp rating would be 115A.

If I follow my intuition, we should load the wires/breaker to 80% of their capacity. Do I want to have higher capacity wires than breaker? Like if I use a 125A breaker, do I need to use 1/0 AWG wire?

Normally I'd go over to our electrician but this old fella is only here very early in the morning a few times a week and we need to make a decision.

Thanks for your time!
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
This probably should be moved to the canadian forum since the answer might be different than for US.

NEC answer:

Conductor ampacity is sized not less than 125% of the full load current found in the charts in the NEC, not the FLC found on the motor nameplate.

The circuit breaker can be sized up to 250% of the FLC found in the chart.
 
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