Single phase motor wiring


Old 02-07-08, 08:04 PM
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Join Date: Feb 2008
Posts: 2
Single phase motor wiring

I have a new compressor to wire. 7.5hp single phase. For 230V NEC chart (??? I looked it up before but I dont have it in front of me now ) says 40A for FLC. Conductors sized to 125% of FLC = 50A so 8 gauge THHN. Short circuit/ground fault protection 150-300% of FLC so 60A breaker. Does this mean it is ok to run a 60A or bigger breaker on #8 THHN (55A) !?!?
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Old 02-07-08, 09:15 PM
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,808
Yes it is allowed to do this due the code have specal section related to the motor useage you can use 60A breaker for 7.5 HP(1) 230v motor with #8 THHN/THWN wire[s].

and make sure you put a disconnection switch right next to the compressor unless the breaker box is in line of sight of it [ 50 feet or less without any obstacales in the way ]

but i rather have a disconnection switch mounted for safety reason anyway.

Merci, Marc
Old 02-08-08, 06:06 AM
Thread Starter
Join Date: Feb 2008
Posts: 2
thanks for the reply. i have the disconnect ready.

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