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Old 08-05-2009, 12:06 PM   #1
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240 Volt Air Compressor


I am attempting to install a 60 gallon, 3.2 hp, 240 volt Craftsman air compressor into my attached garage. I am trying to run a 240 volt circuit from the house breaker box located on the back wall of the house about 50 feet away from the garage. My plan is to run the circuit through the attic and into the garage to a 240 volt outlet (compressor will be plug in). What gauge wire do I need to use? I have a 100 foot 10 AWG heavy duty extension cord. It is flame, water and oil resistant. Can i cut to length and use this to wire the compressor? Do I need to use any conduit? Do I need any kind of a disconnect switch? I am in California if this matters.
Thank you in advance.


Last edited by aj_racing7; 08-05-2009 at 12:08 PM.
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Old 08-05-2009, 01:15 PM   #2
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240 Volt Air Compressor


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Originally Posted by aj_racing7 View Post
I have a 100 foot 10 AWG heavy duty extension cord. It is flame, water and oil resistant. Can i cut to length and use this to wire the compressor? Do I need to use any conduit? Do I need any kind of a disconnect switch?
Thank you in advance.
Don't run extension cords in attic.Why not do it right and run a 60 Amp Circuit or 100 amp To a Sub Panel into the attached garage.. Then you Will be able to add what you want( Lights, Receps). You don't need a disco for air compressor if it plugs in .

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Old 08-05-2009, 01:46 PM   #3
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240 Volt Air Compressor


Thank you for the reply. I already have lights and such in the garage. I just wanted to wire one 240 outlet for the compressor and I don't really see adding anything else in the near future. I was asking about the extension cord because I have it. I thought I could use it instead of buying bulk wire from a spool or Romex if 10 gauge was acceptable for this setup. My thinking is that the difference between the extension cord and bulk wire is the connectors on the ends of the extension cord. If they are removed then they are basically the same thing, right? If this is not ok I will buy the correct wiring. I just need to know what size, and should I use conduit? Thanks again.
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Old 08-05-2009, 02:01 PM   #4
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240 Volt Air Compressor


Thats right, no ext. cords in permanent applications. Sorry you just cannot do it.
You need a minimum of a 30 amp circuit for this motor. The FLA (amps) are around 17. (17 X 1.75) = 29.75. So a 30 amp double pole breaker and #10 wire is what you will need. Does the compressor have a plug on it? If it does it should be rated at 30 amp/250 volt. Is this what you have?
Run the cable (NM) 10/3 or 10/2 from the panel to a junction box. (You can use 10/2 or 10/3). I would run 10/3 regardless. Install a receptacle that matches the plug you have on the compressor. If the compressor does not have a factory installed cord and plug, let us know.

Note. 10/3 will leave you with one extra wire. Just put a wirenut on it and tuck it into the box.

Last edited by J. V.; 08-05-2009 at 02:08 PM.
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Old 08-05-2009, 02:20 PM   #5
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240 Volt Air Compressor


Thank you for clearing some things up. It does not have a factory installed plug.
What is the benefit of using 10/3 if the extra wire is not used? Is this for later upgrading? Thanks.
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Old 08-05-2009, 03:56 PM   #6
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240 Volt Air Compressor


10-3 For future so you will have a neutral wire (Price not much different) If it does not have a plug I would put a 220 switch close to the compressor.
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Old 08-05-2009, 05:13 PM   #7
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240 Volt Air Compressor


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Originally Posted by J. V. View Post
Thats right, no ext. cords in permanent applications. Sorry you just cannot do it....
No argument here. Extension cords are not to be used as permanent wiring.

Quote:
...You need a minimum of a 30 amp circuit for this motor. The FLA (amps) are around 17. (17 X 1.75) = 29.75. So a 30 amp double pole breaker and #10 wire is what you will need....
Where are you getting this information from? I agree with the FLA being around 17, but this means that the circuit for this unit could be wired with a 12-2 cable. It also means that a singe NEMA 6-20R receptacle could be used as the required disconnect.

It also means he could use a 30 or even a 40 Amp breaker on that #12 wire.

12-2 wire is a LOT cheaper than 10-2 or 10-3. No need to spend the extra $$$ for unneeded capacity here.

I would ask the OP to clarify the rating of this compressor: Can you give us the specific information as shown on the nameplate of the unit?

Please post the following and let us know if the item is listed but left blank:

HP rating
Amps
Volts
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Old 08-05-2009, 05:18 PM   #8
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240 Volt Air Compressor


Is this your compressor?
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Old 08-05-2009, 06:16 PM   #9
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240 Volt Air Compressor


Ok. I capiche on the extension cord deal. Yes, that is my compressor.

3.2 hp
15 amp minimum
240 volt single phase

So, should I use 10 or 12 gauge?

That is the first time I have seen the bit about hard wiring it. I looked all through the owner's manual for something about wiring a cord but never found anything.

Once again thank you for all of your input.
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Old 08-05-2009, 06:46 PM   #10
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240 Volt Air Compressor


While 12-2 would be acceptable, I guess I don't like the idea of protecting it at 30 A. I would run 10-2 from a 30 A breaker to a 60 amp A/C disconnect, and whip out to the compressor with seal tite.
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Old 08-05-2009, 07:27 PM   #11
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240 Volt Air Compressor


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While 12-2 would be acceptable, I guess I don't like the idea of protecting it at 30 A. I would run 10-2 from a 30 A breaker to a 60 amp A/C disconnect, and whip out to the compressor with seal tite.
Note that the manufacturer's specs say "15A minimum" - which doesn't jive with the HP rating. Most consumer-market air compressors are given HP "ratings" that are grossly inflated and have almost nothing to do with the actual HP output of the motor during operation. You have to go by the nameplate current to get an idea of the actual requirements. It says 15A, and that can be believed - a 20A breaker on #12 wire should be more than sufficient.

Campbell-Hausfeld got sued in a class action for this a few years back, since they were apparently just picking random impressive numbers for their HP ratings. They agreed to stop, and now rate their compressors using an unrealistic HP number that is still not in compliance with industry standard measurement practices, but has some basis in testing. It's like the peak power produced by the motor immediately before stalling, or something.
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Old 08-05-2009, 08:03 PM   #12
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240 Volt Air Compressor


Quote:
Originally Posted by aj_racing7 View Post
Ok. I capiche on the extension cord deal. Yes, that is my compressor.

3.2 hp
15 amp minimum
240 volt single phase

So, should I use 10 or 12 gauge?

That is the first time I have seen the bit about hard wiring it. I looked all through the owner's manual for something about wiring a cord but never found anything.

Once again thank you for all of your input.
12-2 is more than adequate in this case. As someone else pointed out, those HP ratings may be inflated a bit, since some manufacturers want to make it look like their compressors are more than they are. Is that HP rating on the motor itself, or posted elsewhere on the unit? Look at the nameplate on the actual motor. Betcha a dollar to a donut the HP rating is blank ....
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Old 08-05-2009, 09:08 PM   #13
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240 Volt Air Compressor


The nameplate actually says '3.2 hp Tested per ISO 1217', whatever that means. The nameplate also reads 13 amps.
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Old 08-05-2009, 10:07 PM   #14
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240 Volt Air Compressor


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The nameplate actually says '3.2 hp Tested per ISO 1217', whatever that means. The nameplate also reads 13 amps.
With a 13 amp load, you woould need 12/2 and a 20 amp circuit. I don't see how they can list a 15 amp circuit min.
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Old 08-05-2009, 10:55 PM   #15
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240 Volt Air Compressor


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With a 13 amp load, you woould need 12/2 and a 20 amp circuit. I don't see how they can list a 15 amp circuit min.
If it draws 13 A, then I would use a 20 A circuit. But then again, I have seen some compressors struggle to start and pop a 20 A breaker. I might still run a 25 or 30 A circuit. I'd just have to be there, I guess.

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