Questions on wiring a 220v compressor

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Old 02-25-19, 07:55 AM
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Questions on wiring a 220v compressor

Good morning, first post here and needing some help. I'm hooking up a 220 volt compressor that doesn't include a cord and need to make my own. I ran 10/2 romex wiring from a double pole 30 amp breaker to my garage (about 30' run) where I added a 240v receptacle, which I am using for a heater.

My question is this: I want to know if it is safe to use 10/2 UF romex wire directly from the compressor to my 240v receptacle, which will be about a 30' run. The reason I am concerned, is the literature that came with my compressor says max allowed cord length is 6'. Which doesn't really make sense to me since there would be a run of wiring from whatever the 6' cord is plugged into to the breaker panel.

I want to be able to swap plugs from my heater and air compressor in the winter months.

Thanks!
 
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Old 02-25-19, 08:07 AM
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What is the actual HP rating on the motor from the nameplate? This will determine the cord size you need. You generally should only use flexible cords for a short distance. Romex NM-B cable cannot be used for a flexible use because it contains solid copper wire and is not suitable for vibration or regular movement.

There are two options here.

1) Use 10-2 to run from your existing 30A receptacle box to a second receptacle box next to the compressor. Make up a 6' cord for the compressor and leave it plugged in to the new receptacle box. It's then up to you to make sure to use only one at a time to avoid tripping the breaker.

2) Make a long cord for the compressor. The cord will likely need to be a larger size to account for the extra feet of cord. For example if the compressor requires a #10 flexible cord, you'd want to increase to #8 flexible cord to make the 30' run.
 
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Old 02-25-19, 08:22 AM
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You can not use Romex in any form as an extension cord.
 
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Old 02-25-19, 10:12 AM
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Thank you for the suggestions. The motor is 3.7, here is the exact model:
https://www.homedepot.com/p/Husky-60...602H/205389936

What about if I used the 10/2 to it's own new breaker in the box to a new receptacle next to the compressor then used a 6' cord to the compressor. That seems like the best case solution I'm guessing. Just was trying to avoid running all that wire again. If done this way, should I just use a double pole 30 amp breaker?
 

Last edited by pcboss; 02-25-19 at 04:06 PM.
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Old 02-25-19, 10:25 AM
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The new option will work. But you still can't use romex on the compressor if you use a plug. Romex will be fine if hard wired and properly protected and fastened.
 
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Old 02-25-19, 10:31 AM
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I understand now about Romex as a power cord. I was thinking of 6' length SOOW 10/2?
 
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Old 02-25-19, 10:40 AM
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I was thinking of 6' length SOOW 10/2?
You need 10-3, black white green. (Unlike with cable you do include the ground in the spec quote.)
 
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Old 02-25-19, 10:48 AM
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I thought of another easier option, is this safe to do: purchase 30' of SWOO 10/3 and basically make it a long extension cord. One end would be wired to the compressor and the other to the plug which I would switch out with the heater?
 
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Old 02-25-19, 10:50 AM
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If the motor data plate shows 3.7HP the compressor needs to be hardwired, no plug and outlet. Max HP for plug-in is 3HP. This is why the compressor doesn't come with a cord and plug. You can wire the compressor to a junction box using an A/C whip. If the breaker panel is not in sight of the compressor there needs to be a disconnect within sight of the compressor. If you don't care about following NEC requirements then forget what I said.
 
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Old 02-25-19, 01:09 PM
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Thank you Pattenp for the info. My breaker panel is in the basement and compressor is upstairs in the garage. So say I use an A/C whip to connect the compressor to a junction box, then run my 10/2 romex wire from that junction box to my 240v receptacle box where my heater outlet is. Would that be good? I would just have to be sure not to have them both plugged in together.

Page 5 of the owners manual below talks about the recommendations:

https://images.homedepot-static.com/...c8b46f21bc.pdf
 
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Old 02-25-19, 01:25 PM
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Yes that plan is pretty close, but you need a disconnect. Instead of the plain junction box next to the compressor use an air conditioner pull-out disconnect box ($7). This meets the code requirement for a lockable disconnect. The purpose is so you can ensure a physical disconnect of power while you are changing the belt or some other service where you stick your hands in the machine. If you don't have a cord-and-plug (which this machine is too big for), then a disconnect box is required.
 
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Old 02-25-19, 01:47 PM
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Great, thank you ibpooks! I truly appreciate all the help from everyone!!
 
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Old 02-25-19, 03:19 PM
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The question is if the motor is a true 3.7HP. By the specs in the PDF I doubt it because the install instructions say 20A minimum circuit. You are fine using a plug connection. Also is the outlet you added within sight of the compressor? If so the plug can be the disconnect. You should use cord with a plug on it from compressor to outlet instead of using UF if that works for you..
 
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Old 02-25-19, 07:42 PM
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Patten, that would definitely be the easiest for me! I'll return the UF 10/2 and get a power cord in 10/3. Probably use conduit like this:
https://www.homedepot.com/p/AFC-Cable-Systems-1-2-x-25-ft-Non-Metallic-Liquidtight-Conduit-6002-22-00/202286718?MERCH=REC-_-mobileweb_navplp_rr-_-NA-_-202286718-_-N
 
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Old 02-26-19, 07:09 AM
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What you linked is not a cord and you will find it very difficult to add a plug. Are you trying to run the wire as if leaving it in place and just plugging it in when needed.

Edit: I now get what you are thinking of doing is putting the cord in conduit. You are mixing apples and oranges. Maybe you should just tap off the existing outlet and add another outlet close to the compressor and use a short cord with a plug to connect the compressor.

Even installing two 30A outlets on a single circuit violates the International Residential Building Code, but it may be the lessor of two evils. Unless you're worried about code.

You could run a jumper circuit from the compressor back to the existing outlet and install a power inlet next to the existing outlet and use a short 2' or so jumper SO cord to connect the inlet to the outlet. That way you have the way to prevent both the heater and comp being connected at the same time.

With all that said, sounds like you should run a new circuit for the compressor.
 

Last edited by pattenp; 02-26-19 at 07:26 AM.
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Old 02-26-19, 07:12 AM
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Yes, I was going to run the cord through that conduit along the wall to where the outlet is, and have the plug end hang near the receptacle so I can switch with my heater during the cold moths.
here is the cord I will use:

https://www.homedepot.com/p/Southwire-By-the-Foot-10-3-300-Volt-CU-Black-Flexible-Portable-Power-SJOOW-Cord-55812599/204633009
 
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Old 02-26-19, 07:36 AM
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I don't think that cord will fit in that 1/2' flex. If you are just using the conduit to have a chase to keep it in place and protect the cord then why not use 3/4" rigid PVC conduit. You want conduit large enough the wire doesn't fill it up, leave at least a third or so open space in the conduit. You need airspace to release heat.
 
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Old 02-26-19, 07:46 AM
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Ah, didn't even think about that. I was thinking about keeping costs down but I like the idea of the PVC, which isn't too expensive either. Schedule 40 should be sufficient, correct?
 
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Old 02-26-19, 08:09 AM
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Sch 40 is okay. Unless you want the added protection of Sch80.
 
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Old 02-27-19, 10:37 AM
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All done, thank you again for all the help!
 
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