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Thread: Wiring For Compressor Help...

  1. #1

    Wiring For Compressor Help...

    So, the compressor I'm getting specs at 16.2A. Will I be OK using a 20A circuit, with 12ga. wire? I'm hoping that's the case, as I currently have a 20A 220v receptacle I can run off of.

  2. #2
    12 gauge is rated for 20 amps. I'm not an electrician but I believe it is best practice to size circuits for power tools as if they are "continuous loads". That is, the circuit should be rated for 125% of the actual load. 16.2 amps x 1.25 = 20.25 so technically, you over 20 amps. I don't know if that's a problem in the real world.

  3. #3
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    Quote Originally Posted by Derek Arita View Post
    So, the compressor I'm getting specs at 16.2A. Will I be OK using a 20A circuit, with 12ga. wire? I'm hoping that's the case, as I currently have a 20A 220v receptacle I can run off of.
    Hi Derek,
    Your 20 Amp circuit with the 12 gauge wire will be fine for this application.
    David

  4. #4
    I got more curious about this and found this. As usual on forums, there is some disagreement...

  5. #5
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    In this case, the compressor would not be considered a "continuous" load. The highest current draw is at start-up and the duty cycle will most certainly be less than 50%, probably more like 10% or less. As an Electrical Engineer with many years of experience in this area - the 20 amp circuit will be fine for this application.
    David

  6. #6
    Here's more info on the compressor...it's rated at 3.7 running HP...https://www.lowes.com/pd/Kobalt-60-G...sor/1000542193

  7. #7
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    I saw your question earlier but did not reply.

    My my first thought was about my tractor tires. They are rated for 16.2 psi. My compressor maxes out at 20 psi. Will my compressor supply what my tires need? Of course it will.

    Your 20 amp circuit will too. Previous responses are valid. Remember, a compressor is not a continuous load.

    You will be fine.

    Edit: of course I made up those numbers to make a point. I think I run about 12 psi in my tractor tires...
    Last edited by Bill Space; 06-19-2019 at 4:03 PM.
    Too much to do...Not enough time...life is too short!

  8. #8
    I was concerned, because I've read that a machine may be rated at X amps, but peak would be higher than that, like at start up. Also, Kobalt recommends a 30 minute brake in.
    OK...just read up on my 3hp table saw. At the time I got it, everyone said I needed a 30A circuit. The PM site recommends a 20A circuit for the 14.5A it needs. Did over provide?
    Last edited by Derek Arita; 06-19-2019 at 4:27 PM.

  9. #9
    Put it on the circuit and see what happens. If it runs fine and doesn't trip the breaker you're all good. If it trips the breaker on start up because of the extra draw needed, you'll need to get a 30 amp circuit to run it. 12 gauge wire will supply the current the compressor needs to draw while running. It will absorb the start up current without a problem.

    I have a Campbell Hausfeld compressor and I believe it's about a 4HP motor. Says 2.98KW output divide that by 746w/HP and you get about 4HP. I've been running it on a 20 amp circuit for 14 years now.

  10. #10
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    It depends on how long the wire is from the panel. If it is under 50 feet, one way, you should be fine.
    BILL D

  11. #11
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    Guys, please don't be saying stuff like '#12 will be just fine' unless you know for a fact that the NEC says that it's fine. This is an area of the electrical code that is far more complex than most realize. The ampacity of #12 wire depends on the temperature rating the insulation, number of wires in the conduit and the termination temperature rating of the breaker or device at the load end of the circuit. And a motor load is more complex than a standard receptacle or lighting circuit

    I'm not going to say yes or no on this, because I'm a Canadian electrician. The NEC & CEC are largely harmonized, but not completely & I don't have access to the NEC. I'm just posting this because inexperienced people tend to get fast & loose with code requirements that do need to be adhered to.

    Please don't take offence with my comments, because that is not my intent.

  12. #12
    Frank, thanks for the reply. I don't think it's a cut and dry call. That's why I'm here asking. I may end up erring on the side of caution, even though it means running another 30A line. I do take your caution seriously.

  13. #13
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    I don't know about Canada, but in the US, much of the NEC is written for industrial applications rather than domestic plug in installations. The NEC does not always apply to home shop environments. In this application, I would go by whatever the owner's manual specifies.

    Quote Originally Posted by Frank Pratt View Post
    Guys, please don't be saying stuff like '#12 will be just fine' unless you know for a fact that the NEC says that it's fine. This is an area of the electrical code that is far more complex than most realize. The ampacity of #12 wire depends on the temperature rating the insulation, number of wires in the conduit and the termination temperature rating of the breaker or device at the load end of the circuit. And a motor load is more complex than a standard receptacle or lighting circuit

    I'm not going to say yes or no on this, because I'm a Canadian electrician. The NEC & CEC are largely harmonized, but not completely & I don't have access to the NEC. I'm just posting this because inexperienced people tend to get fast & loose with code requirements that do need to be adhered to.

    Please don't take offence with my comments, because that is not my intent.

  14. #14
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    Quote Originally Posted by Art Mann View Post
    I don't know about Canada, but in the US, much of the NEC is written for industrial applications rather than domestic plug in installations. The NEC does not always apply to home shop environments. In this application, I would go by whatever the owner's manual specifies.
    Local codes will always trump the owner's manual, at least as far as minimum requirements go.

  15. #15
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    In the installation instructions for the compressor it states that 12 gauge is the minimum wire size up to 75 feet. It also states check your local codes. As far as local codes trumping owners manual I can't count the number of times the inspector looked thru the install instructions of a piece of equipment to get the answer about electrical requirements or clearances.

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