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Old 04-25-2012, 07:33 AM   #1 (permalink)
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Shop air compressor wiring

I'm about to wire up a new air compressor at the new shop. It has a breaker housed in the panel on the compressor. Do I need a separate fused disconnect on the wall or can I wire straight to the compressor panel?

Breaker on bottom.
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Old 04-25-2012, 08:04 AM   #2 (permalink)
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once you figure it out, you can come run a panel for me to put in a new compressor too!
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Old 04-25-2012, 10:13 AM   #3 (permalink)
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once you figure it out, you can come run a panel for me to put in a new compressor too!
lol.. I forgot you were in OKC! We're on the Northwest side of OKC, just off NW Expressway, barely in Yukon.
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Old 04-25-2012, 12:38 PM   #4 (permalink)
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lol.. I forgot you were in OKC! We're on the Northwest side of OKC, just off NW Expressway, barely in Yukon.


I have a co-worker that lives in Surrey Hills.

I'm at 10th and Sara.
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Old 04-25-2012, 07:16 PM   #5 (permalink)
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That's not a breaker, that's a motor starter.

You need to set a disconnect on the wall, and flex/MC over to the compressor. It appears to be 240v, but you would need to check the nameplate on the motor itself. It looks like you have half a liquid tight flex fitting on there right now. It'd be fine to run that over if you still have the rest of it.

I'd do a 30A fused disconnect with fuses sized for the motor, given it's not a monster. Where are you getting your power from? And did you have a controller other than the pressure switch for it at one point?
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Old 04-26-2012, 08:11 AM   #6 (permalink)
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I have a co-worker that lives in Surrey Hills.

I'm at 10th and Sara.
Cool.. It's looks like were just a few miles away from each other. Sent ya a PM
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Old 04-26-2012, 08:22 AM   #7 (permalink)
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That's not a breaker, that's a motor starter.

You need to set a disconnect on the wall, and flex/MC over to the compressor. It appears to be 240v, but you would need to check the nameplate on the motor itself. It looks like you have half a liquid tight flex fitting on there right now. It'd be fine to run that over if you still have the rest of it.

I'd do a 30A fused disconnect with fuses sized for the motor, given it's not a monster. Where are you getting your power from? And did you have a controller other than the pressure switch for it at one point?
Thanks for the reply. I bought the compressor just as you see it here.

It is 240v, 1 phase, 7.5 HP. I have a disconnect I can use. There are two fittings that go into the side of the box.. not sure why there would need to be more than one set of wires going to it?
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Old 05-04-2012, 08:45 PM   #8 (permalink)
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Sorry it took so long to get back to you. Feel free to PM me and remind me with questions.

So, first with 7.5hp you'll want some 30A fuses. Preferably time delay so you don't have to worry about in-rush current and nuisance "tripping". Also, you'll need some #10 AWG wire for 30 amps. I prefer stranded for a high vibration application like this, but solid works fine also.

Is the pressure switch still wired in? It doesn't appear to be. You'll need to wire it into the coil to pull in the contacts and start the motor. OR, they may have used a manual start/stop station to over-ride the pressure switch if they wired the pressure switch in series. This would be the second conduit.

The lugs on the top are your line-in. You'll land your 240v here. Also remember to hook all your grounds up and ground the enclosure for safety. You'll need to see if your coil is 120 or 240v. If it's 120v you'll also need a neutral from your panel.

Sorry if this sounds confusing as hell, I almost never use square D starters and I'm one of those people that could have you going in 5 minutes if I was there. Just bad at explaining without visual aids.

Could you snap a few more pictures of the whole compressor and the starter?
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Old 05-10-2012, 11:19 PM   #9 (permalink)
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I can definitely get a few more pics when I get back in town. I have a pretty good idea what you are explaining though.

Thanks for the help!


Quote:
Originally Posted by chevy_man View Post
Sorry it took so long to get back to you. Feel free to PM me and remind me with questions.

So, first with 7.5hp you'll want some 30A fuses. Preferably time delay so you don't have to worry about in-rush current and nuisance "tripping". Also, you'll need some #10 AWG wire for 30 amps. I prefer stranded for a high vibration application like this, but solid works fine also.

Is the pressure switch still wired in? It doesn't appear to be. You'll need to wire it into the coil to pull in the contacts and start the motor. OR, they may have used a manual start/stop station to over-ride the pressure switch if they wired the pressure switch in series. This would be the second conduit.

The lugs on the top are your line-in. You'll land your 240v here. Also remember to hook all your grounds up and ground the enclosure for safety. You'll need to see if your coil is 120 or 240v. If it's 120v you'll also need a neutral from your panel.

Sorry if this sounds confusing as hell, I almost never use square D starters and I'm one of those people that could have you going in 5 minutes if I was there. Just bad at explaining without visual aids.

Could you snap a few more pictures of the whole compressor and the starter?
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Old 05-11-2012, 07:13 PM   #10 (permalink)
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Quote:
Originally Posted by Azzy2000 View Post
I'm about to wire up a new air compressor at the new shop. It has a breaker housed in the panel on the compressor. Do I need a separate fused disconnect on the wall or can I wire straight to the compressor panel?

Breaker on bottom.
looks like everything is wired, meaning presure switch to coil, is the motor wired to the box housing the starter/contactor? if so just bring supply power "line power" to the terminals labled L1, L2. yes a disconnect is required, unless you make a plug connection. ie receptacle/ plug.
the contactor is the black thing in the box you took a pix of. the pressure switch tells the contactor to turn on and turn off. imagine the black thing in the box as a switch, follow the conduit or flex/mc from the motor and the wire in it to the box. is it there?
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