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  1. #1
    Join Date
    Sep 2007
    Posts
    177

    Default A/C compressor

    I need to move my outdoor AC compressor unit. When I started looking into how it is wired I found some things that puzzled me. I was hoping someone with more experience could set me straight.

    The line from the main breaker panel is aluminum 230V single phase, 2 pole on a 50 amp dual pole breaker. The line runs ~ 40 feet into a load box where it switches over to copper. That box has a 40 amp two pole breaker. The copper line runs outside to Square D box that has something that looks like a single pole breaker...but there is no amp rating on the switch. This leads out to a fairly new (4 years old) compressor which I believe uses something that looks like 14 gauge wire (or maybe even lighter) for a screw compressor. It seems to me the amount of power supplied to this unit is way over board for what is needed.

    So here are my questions.

    1. Do the second and third breakers/switches need to be there? What is the rationale (if any) for them being there?
    2. As I am moving the compressor, can I install a junction box inside, switch over to copper at the correct gauge for the compressor and put in a lower rated breaker at the main panel?
    3. I am moving the compressor away from the house so there will be no nearby surface to mount anything. Is this OK (to not have a switch box near the compressor) or do I need to put in a post near the compressor for mounting that external switch box?

    Thank you for any help anyone can give.

    -Walt

  2. #2
    Join Date
    Mar 2009
    Location
    wisconsin
    Posts
    159

    Default Re: A/C compressor

    well im not sure why the circuit is going to the second breaker box. The third one that you described is a local disconnect. Im guessing its an unfused one. You do need that disconnect within site of or within 25 feet of the compresor.

    with out all the compressor info its hard to tell what you need for wire size. 14 guage does seem small. unless it was sent with the unit itself, as if it were a factory set up

  3. #3
    Join Date
    Sep 2007
    Posts
    177

    Default Re: A/C compressor

    Regarding the switch box near the AC unit....does that box have to be visible from the AC unit? I could mount the switch box inside the house that would be within 25 feet.

    If the box does need to be visible from the AC unit, how is the box typically mounted when the unit is away from a wall? I was thinking of running conduit to the unit to get the freon lines out from the house. I was hoping to run the electrical lines in the same conduit. The idea was that the conduit would pop out of the ground near the unit and the line would run into the unit. Would a PT post positioned nearby provide an adequate means to mount the switch box (assuming it is all watertight)?

  4. #4
    Join Date
    Aug 2007
    Posts
    7,195

    Default Re: A/C compressor

    My local codes require that there be a disconnect at the unit itself. Heck, our AC is right next to the main panel and there is STILL a disconnect on the wall behind the AC unit. Odds are your local code requires the same disconnect be within 3' or 4' of the unit.

    As for having to run through sub-panels, how you power up the unit from your main is up to you. All the installations I've ever seen have been fed directly from the main panel. If you've got sub-panels, it's possible that your main is not rated for the load OR it was an afterthought and added later with other electrical needs.

    I know you like to do stuff yourself, but if it were me, I'd consult with a local electrician. At the very least, check with your building department to see what is required in your area.

    BTW, good to see you again Walt. We miss not having you around.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  5. #5
    Join Date
    Mar 2009
    Location
    wisconsin
    Posts
    159

    Default Re: A/C compressor

    Yes the disconnect needs to be within site of the unit. the whole idea is safety for who ever would happen to be working on it. Someone could go flip the breaker on while your working on it, and you would never know.

    Id mount the disconnect right to the unit itself if it was me. then just chase through it.

  6. #6
    Join Date
    Aug 2011
    Location
    Northern Indiana
    Posts
    78

    Default Re: A/C compressor

    The A/C unit will have a label stating the minimum ampacity of the wire required and the maximum ampacity for the circuit breaker.

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