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waltdeckhouse
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

sparky1
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

waltdeckhouse
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)?

A. Spruce
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.

sparky1
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.

Brad
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.

Re: A/C compressor

Walt,think of the large first breaker in the main panel as the most unlikely place a breaker on that circuit will trip. It has to protect the wire on that circuit which feeds the next smaller breaker.

The second breaker (smaller than the first) will most likely trip if the compressor draws too much current. Since it is smaller than the 1st breaker the wire it protects can also be smaller.

The way you described the last "breaker" if you look at it closely it may say something like "does not provide overcurrent protection" so it is simply a disconnect, which is required within 25 ft of the compressor (and in-sight of it).

All disconnects have to be within 25 ft of and in-sight of the their associated equipment.

The only reason to have the 2nd breaker is to make it more convenient to reset.

Most A/C units require Copper wire (CU) and the nameplate will state: the minmum breaker size and the maximum size, I usually use large enough wire to use the largest size breaker allowed.

I too believe the #14 wire may be too small, if the compressor draws more than a constant 12A, and may actually cause the compressor to fail. But, the small, newer units actually state a 15A breaker is the max. allowed. Read the nameplate.

Good Luck from Columbiana, Alabama
Maurice Turgeon,http://thesemi-retiredelectrician.com

JLMCDANIEL
Re: A/C compressor

Is it possible that an older higher amperage unit was replaced and the second breaker was installed per the new requirements while leaving old wiring in place? You could mount a cut off switch on the unit itself if you can find a place that won't puncture the lines.

Jack

Mastercarpentry
Re: A/C compressor

Service disconnects should never be mounted to the units they serve. This logic is simple- you'll have to deal with exposed hot wiring if you replace the unit- the very thing the disconnect box is supposed to prevent! Probably a low-level pole mounted disconnect box w/conduit next to the unit will meet code and look OK but always check. Codes change with time and vary by locale.

Phil

Brad
Re: A/C compressor
The Semi-Retired Electric wrote:

Walt,think of the large first breaker in the main panel as the most unlikely place a breaker on that circuit will trip. It has to protect the wire on that circuit which feeds the next smaller breaker.

The second breaker (smaller than the first) will most likely trip if the compressor draws too much current. Since it is smaller than the 1st breaker the wire it protects can also be smaller.

The way you described the last "breaker" if you look at it closely it may say something like "does not provide overcurrent protection" so it is simply a disconnect, which is required within 25 ft of the compressor (and in-sight of it).

All disconnects have to be within 25 ft of and in-sight of the their associated equipment.

The only reason to have the 2nd breaker is to make it more convenient to reset.

Most A/C units require Copper wire (CU) and the nameplate will state: the minmum breaker size and the maximum size, I usually use large enough wire to use the largest size breaker allowed.

I too believe the #14 wire may be too small, if the compressor draws more than a constant 12A, and may actually cause the compressor to fail. But, the small, newer units actually state a 15A breaker is the max. allowed. Read the nameplate.

Good Luck from Columbiana, Alabama
Maurice Turgeon,http://thesemi-retiredelectrician.com

Where can I find your documentation on your "25' " rule? Code article please.

waltdeckhouse
Re: A/C compressor

Thank you to everyone for the useful information.

I talked to a local HVAC guy and he says that there must be a local disconnect either near the unit or within line of sight. My plan is to put a post near the unit and mount the disconnect and the box the local power company uses to control usage. BTW...the box near the unit (as it currently sits) is a disconnect...not a circuit breaker.

The second breaker box is where the wire switches over from aluminum to copper. I believe this box was installed at some later date after the original install (there are hints that things changed over the years). I had a new unit installed ~ 5 years ago....and this unit has the much smaller gauge wire internal. I need to chase the gauge down so I am not adding confusion to the discussion.

My plan is to move the unit away from the house by about 16 feet. I plan on installing a conduit to run the compressor lines and electrical wires out to the unit. I plan to use the second breaker box as a place to start the wiring to the new location. I plan to move this breaker box into a nearby utility closet. this box has room for only one breaker and is used only for this AC unit. Does anyone know if there are any regulations that would govern me NOT putting the breaker box in a utility closet?

-Walt

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