Compressor wiring

[tiggi]

Hi all,

Need an advice on running a dedicated line for the compressor. The motor on the compressor is 5hp 230v 20.8A full load. The run is going to be about 40 feet through conduit. Am I safe using #12 copper wire with 30A breaker on the sub-panel?

Please and thank you!

 

[Dagny]

No. 10 awg. Not really a five HP but lots of air compressors are like it.

 

[tiggi]

No. 10 awg. Not really a five HP but lots of air compressors are like it.

What do you mean "Not really a five HP"?

 

[alfredeneuman]

There's at least 2 threads on this very subject

Here's one that has the same specs as your compressor

http://www.garagejournal.com/forum/showthread.php?t=268621

 

[Falcon67]

But he was right about the #10. 5 HP @ 240 is more like 16a calculated but the name plate is the ruler.

 

[tiggi]

Yea i was going by the nameplate. Thanks for the info guys.

 

[tiggi]

Also is there a difference if I use NM-b or THHN wire?

 

[pattenp]

Also is there a difference if I use NM-b or THHN wire?

Yes. The temperature rating is different. NM-b has to be sized @ 60C whereas THHN can be sized @ 75C. So for the compressor circuit #10 NM-b is 30 amps and #10 THHN is 35 amps.

This does not apply for general branch circuits because small conductor rules kick in and #10 Cu is limited to 30 amps.

 

[tiggi]

So would it be ok if I use #12 THHN?

 

[Norcal]

No, you should not.

 

[Aceman]

So would it be ok if I use #12 THHN?

Do us a favor, if you're going to start a thread asking how to wire a 5HP compressor despite the fact there are many threads that have been already answered with the same question, at least read the responses you get.

Where did anyone say recommend anything less than #10?

Just so we're clear, #12 is NOT ok!

Jeez, some people are so helpless.

 

[pattenp]

So would it be ok if I use #12 THHN?

By the NEC, no. If using the FLA of 20.8 X 1.25 = 26A. #12 Cu THHN is 25A. Just to be clear, does your compressor motor label list the HP is 5 or SPL?

Are you trying to squeeze by with the bare minimum?

Read this thread...
http://www.garagejournal.com/forum/showthread.php?t=268987



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