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Old 02-20-2010, 05:38 PM   #1
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Compressor Question


I have an Ingersoll Rand 80 gal 5 HP compressor that is 220 or 230. When an electrician hooked it up for me in my shop he used 10 gauge. Is it necessary to use 10 gauge or would I be fine with 12 gauge? I have searched all over the net for the manual to my compressor and can't find it.

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Old 02-20-2010, 06:14 PM   #2
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There should be a placard on the compressor that states power requirements - what does it say? Did the electrician see the unit? He likely sized the circuit off the unit.

It probably draws around 20a or more running - more at start-up, so would go on a 30a breaker with #10 wire - #12 would be a 20a breaker and not enough circuit.


Last edited by vsheetz; 02-20-2010 at 06:16 PM.
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Old 02-20-2010, 07:19 PM   #3
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Compressor is motor circuit. It works on different rules than standard circuits. Even if it is 30 amp it might be able to be installed on #12. I'm not that up on motor circuits but I do know you are allowed smaller wires for them than normal circuits if you wish.
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Old 02-20-2010, 09:50 PM   #4
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Suggest to contact Ingersoll Rand for their recommendations if you can't find a manual and definitive answer.
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Old 02-20-2010, 09:54 PM   #5
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Why can motor circuits have smaller wire?
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Old 02-20-2010, 09:55 PM   #6
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Compressor Question


Not likely that a 5 hp motor will be able to use #12 awg. If you have no motor manual then the compressor would be wired to the motor rules of the NEC. A 5 hp motor has an FLC of 28 amps at 230 volts. The minimum ampacity for the wires in the branch circuit would be 1.25 x 28 = 35 amps. The minimum wire you could get by with is #10 awg.
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Old 02-21-2010, 12:00 AM   #7
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Compressor Question


Quote:
Originally Posted by joed View Post
Compressor is motor circuit. It works on different rules than standard circuits. Even if it is 30 amp it might be able to be installed on #12. I'm not that up on motor circuits but I do know you are allowed smaller wires for them than normal circuits if you wish.
No. Not smaller than the FLA (Full load amperage) of the motor! You're allowed to oversize the protection by 25% (125% of FLA) due to starting draw, which falls back to normal rating after initial starting surge!!
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Old 02-21-2010, 12:12 AM   #8
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Compressor Question


I have a dedicated 20 amp to my 2hp compressor.

I had a 15 amp at my old place that trip the breaker in cold

weather starts.
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Old 02-21-2010, 06:14 AM   #9
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Originally Posted by spark plug View Post
You're allowed to oversize the protection by 25% (125% of FLA) due to starting draw
Actually, if you use a breaker to protect the circuit you can go up to 250% of the motor FLA. 300% for non-time delay fuses and 175% time delay fuses.

If that comes out to a value of a non standard fuse/breaker rating, you can go to the next higher standard value.

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