Air Compressor

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  #1  
Old 06-05-18, 08:06 AM
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Air Compressor

Hello everyone, Iíve looked on the DIY articles and on the internet and canít come up with a solid at least to my understanding, I bought a new compressor for my shop, itís a 10HP 208v 3phase compressor , it says it pulls 34amps, I have all the wire and conduit ran, just canít figure out what breaker size to use for the main electrical panel and what fuse size for the in line ďsafety disconnectĒ. Iíve read to use breakers 125-200% overload . Any help would be great. Thanks in advanced.
 
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Old 06-05-18, 08:31 AM
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What amp size wire and disconnect do you have? The safety disconnect does not need to be fused. The compressor should have its own built-in overload protection. In most cases the breaker only provides short circuit protection and can be sized up to 250% to handle startup current.
 
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Old 06-05-18, 11:18 AM
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Iím running 8 gauge wire, and I do believe the compressor has its own overload protection, the safety disconnect is a GE fuseable and can be fused to 35 amp or 60amp. I contacted the company that services them and he told me a 70 amp breaker (200% or 175%) but he wasnít 100%. It just seemed really high for me but if the disconnect and breaker only serve as a short circuit protection then I can understand why he said that. So if I get a 70amp safety disconnect , I would do the same with a 3 pole 70amp breaker at the panel right? Or could I simply just fuse the one I have to 60amps and a 60amp breaker?
 

Last edited by LR1992; 06-05-18 at 11:33 AM.
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Old 06-05-18, 11:32 AM
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Based on NEC 10HP 208V 3Ph is 30.8A, so 30.8A X 1.25 = 38.5A, so call it 40A. So #8 Cu THHN in pipe is good. I would just go with a 60A breaker in the main panel and see if you have any tripping on startup. Even if you use a 70A breaker in the main an unfused disconnect can be just 60A rated. If you use a fused disconnect then the fuses should be sized the same as the breaker. If the panel box is within 50ft and in sight of the compressor you don't need a separate disconnect.

Edit: I doubt very much you would have any problems with using 60A breaker and 60A fuse. If it was me I'd dump the fuse and use an unfused 60A rated disconnect.
 
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Old 06-05-18, 01:53 PM
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The main panel is not really in sight of the compressor and the wire run is about 65í or so. I will see what I can find at the local contractor store on the disconnect boxes. I wish I didnít have to use one with how much they cost trust me. But thank you very much for the help, I will try to finish the install tomorrow.
 
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Old 06-05-18, 02:04 PM
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A non-fused 60A 3PH disconnect can be found for about $60.
 
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