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  #11  
Old 09-28-2012, 07:40 AM
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rbibb rbibb is offline
 
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Of course both sides in debate are right to some extent. Simple solution is to put a slo blo fuse or breaker sized to handle motor locally mounted at the compressor that will blow should the motor short or otherwise draw more current than needed in normal operation and let the existing breaker protect the feed circuit.

No need to wire a separate circuit that way.
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  #12  
Old 09-28-2012, 07:49 AM
Wayne Gillispie Wayne Gillispie is offline
 
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Quote:
Originally Posted by ColoRv View Post
I've never seen an air compressor without its own thermal protection. Regardless, the NEC allows for oversize on breakers to allow for startup draw unless something drastic has changed since last I had this discussion with one of our engineers, which I doubt.

I'll not lose any sleep over my compressor running on my welding circuit anymore than I would about my iPhone charging on a 15a circuit, but as in all things we each must live with our own decisions.
I install heat pumps all the time. Your typical split system hp draws 10-12 Amps @ 240 V running, but about 60-80 A starting. The mfr data plate calls for a 30 A breaker. A standard breaker is made to withstand the .5 second starting torque.
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Last edited by Wayne Gillispie : 09-28-2012 at 07:58 AM. Reason: Your electrician knows what he is talking about.
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  #13  
Old 09-28-2012, 11:16 AM
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LAMPSguy LAMPSguy is offline
 
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Obviously there are many ways to skin a cat...I thought this would be easy.

I have not purchased the compressor yet, with being Navy and probably needing to move the shop at least once/twice before it is complete, would I be better off with a 20-30 gal 110V "portable" compressor?

From the sounds of it all these big 240V jobs are supposed to be hard wired in, am I asking for trouble wiring a plug on the end?

Going back to my original question, I figured wiring a circuit for 12 KW of pottery kiln would use thick enough wire so my only worry would be from the plug to the motor no?
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  #14  
Old 09-28-2012, 11:22 AM
David Paule David Paule is offline
 
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No problem with a plug connection, if it's rated for the load.

However, I'd bet that there will be one or two times a month when you'd really like to run both the AC and the kiln at the same time.

Dave
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  #15  
Old 09-28-2012, 12:51 PM
Wayne Gillispie Wayne Gillispie is offline
 
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I built my RV-10 using a 26 Gallon 115/230V campbell hausfeld from Lowes. No worries with wiring and plenty big enough until you want to do fiberglass then you have to take your time. I plumbed in an old lp grille tank to give my system more capacity. It is horizontal on wheels. Built a fiberglass ductboard box around it for noise suppression. Easy to move wherever you want.
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  #16  
Old 09-28-2012, 01:29 PM
Erik.37m Erik.37m is offline
 
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I understand it the Breaker protects the wires and at the end of the run you have a "Thermal overload" contactor. Using the correct "heaters" to trip at the value required to save the motor It's more expensive but if you have a 10 hp motor there well worth it. Pretty standard in manufacturing and highly recommended. Erik
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  #17  
Old 09-28-2012, 01:29 PM
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Captain_John Captain_John is offline
 
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Nick, it sounds like you know you are on the ragged edge if you are asking questions about how to "make something work".

If you want to "make it work" and be legal you will need to install a 4 space can, fuse the smaller #12's at 20 amps and basically do a tap on the 60a line.

That would probably be similar in cost to running another parallel 250v 20a line to the compressor. In other words... not worth the while.

If I were you I would just get a 125v compressor and call it a day.

My two...

CJ
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