wiring a compressor

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Old 03-21-10, 08:32 AM
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wiring a compressor

Hi, looking for some advice here. At my workplace, our compressor went out, so we replaced it with a new one from Home Depot. Old one was 220V. New one is 120V, 15 amp. I used the old wires, 12 ga I believe, and just used a spare 20 amp breaker in the box. Load into breaker, and neutral into neutral bar, and didn't mess with the ground, which is on the ground bar. The metal box also has the ground attached. I used a 15 amp outlet, and after a week, the compressor started tripping the breaker when it started up. The manual states that a 20 amp breaker is sufficient. Any thoughts?
Thanks,
Chris
 
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Old 03-21-10, 08:40 AM
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Motors can draw up to 300% on start up. Compressors can be quite hard to start. If everything seams fine with the compressor (it is not trying to start with full head pressure) it is allowed by code to increase the size of the breaker using the same size wire. A 25 amp breaker will likely solve your problem. However a 25 amp breaker is not common at the big box store. You might have to go to a supplier.
 
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Old 03-21-10, 09:40 AM
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Thanks. I'll look for a 25 amp breaker.
Chris
 
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Old 03-21-10, 09:44 AM
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You may just have a bad 20 amp breaker, but I'd also be inclined to go with a new 25 amp breaker.
 
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Old 03-21-10, 10:46 AM
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If the FLA run of the motor is 15 you can change the breaker to a common 30A. Also, is this wired to a main entrance panel or sub fed type? You need to go to the ground bar in a sub, with the ground wire, no neutral in this setup.
 
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Old 03-21-10, 12:37 PM
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Originally Posted by sberry27 View Post
... Also, is this wired to a main entrance panel or sub fed type? You need to go to the ground bar in a sub, with the ground wire, no neutral in this setup.
Sberry27, in the first post he said it was a 120v compressor so he would need a neutral.
 
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Old 03-21-10, 01:41 PM
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Whoops, missed that, good catch. He can over breaker this if it is a dedicated line for it and no means to plug anything else in to this circuit. Ideally is to get a single outlet vs taping it off like I have been known to do. (on my own equipment)
 
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Old 03-21-10, 01:46 PM
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How can we post picture attatchment?
 
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Old 03-21-10, 01:52 PM
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Originally Posted by sberry27 View Post
How can we post picture attatchment?
http://forum.doityourself.com/electr...your-post.html
 
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Old 03-21-10, 10:16 PM
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there is a device on most compressors built into the pressure switch which eases the pressure off to enable it to start back up against the load of the air...older ones used a very tight spring i have no clue what the science in the new ones is i just know it exists if your pressure switch has a second small flared copper tube running to it then it has this device.. it should be checked IMO
 
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Old 03-21-10, 11:17 PM
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braether3.,

It called unloader valve it will be in the pressure switch for small compressor size for larger one it will be found in the cylinder head { it will pull the reed valves up during freewheeling mode }

and with all compressors if you have unloader valves pay attetion to it when you replace the pressure switch they are pretty picky with it and if unloader valve is clogged you will have hard time to start up the compressor.

Merci,Marc
 
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Old 04-07-10, 08:25 AM
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I am going to wire it in to a 25 amp breaker today. It is on its own circuit. I will look into the unloader valve on the compressor, which is brand new. Thanks.
 
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Old 04-07-10, 09:59 AM
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I had a few happen to me like this. Brand new compressor and all you had to do is plug it in. The best luck I had was to hardwire in to the outlet and do away with the plug & receptacle. This will elimate loose connections on the receptacle & plug. If the distance is great from the compressor to the panel you might have to upsize you wire to a #10. Another thing you might what to do is check all your connections from the panel to the compressor. You did say it work for about a week and started to trip after that. A loose connection could have gotten bad the first week causing this.

Jim
 
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