I have a dedicated circuit for an in-wall AC unit. It has a double pole 15A breaker and at the outlet is a 15A 250V receptacle.

The AC unit I have is a building provided unit (I rent). I just bought a new one since the one I have doesn't cool and costs a lot to run. Anyway, the only units I could find that fit the opening and provide reasonable cooling are < 125V. I bought the one that would fit the opening and is 12,500BTU.

Anyway, I have a good idea how to change out the double pole breaker, but wanted some suggestions. I bought a 15A single pole breaker to replace the double and I have a 125V receptacle already. At the breaker box I need only attach one of the hots to the new breaker, but what do I do with the extra? Do I just cap it off with a wirenut or do I need to tie it into the box's ground block?

At the receptacle there are two wires leading in now, but no ground. At the metal casing in the wall there is a screw that's used for grounding and there's a wire runing from it to a screw on the AC unit's chasis. I'll do the same with the new unit. It seems straight forward (swap out double pole with the single, do something with the extra wire from the double pole, wire in the new outlet, ground the AC unit), am I missing anything?

 

You say 3 wire at the panel and just 2 at the receptacle.
Id take and just make one the ground for 110 on the new receptacle and the other hot and the same in the panel.make The same one the ground there as on the receptacle


Ed

 

First we should point out that legally you're not allowed to do this work, even if your landlord gives you permission. If this place burns down and your electrical work is even possibly connected to the fire, your life as you know it is over.

As Ed points out, there is absolutely no need to replace the breaker. All you have to do is use half of it by moving the white wire off the breaker and onto the neutral bar. Then of course you have to replace the receptacle.

I would suggest, however, that you look harder for a 240-volt unit. A new 240-volt A/C should provide twice as much cooling as a new 120-volt A/C.

 

I had been looking around for a unit to fit the opening in the wall. It's the only option for a place to put it. The opening is about 24" across by 15 7/8" high. All the 240V units I found were too big. I have been to Walmart, Home Depot and some local places and they really don't have much. I decided on Sears, since sears.com has a good selection and had a couple that fit the size of the opening I have. In addition, I can check store inventory from their site. Unfortunately a few days ago they only had one model that was 240V that would fit and they didn't have it at any local stores anyway. Now looking at their site there are hardly any 240V and all of the ones they do have are too large. Asking around a few days ago everyone convinced me it was easy to change to 120V and assured me my landlord should handle it. Nope, they told me to do it myself or call an electrician.

So, anyway, I'm sort of stuck. I'd rather just convert to 120V and not have to find a replacement unit which could take forever and lug the 100lb thing back to my apartment.

For clarification there is one black and one white going into the current breaker and there is one black and one white going into the outlet. Not three at the breaker box.

I understand the liability. That's why I'm asking so I do it right. I would call an electrician if I knew of one around here and if I didn't have to deal with getting building approval and likely having to come here during the day off of work and who knows when they'd be able to come anyway for such a little job.

 

No ethical electrician would do this work for you, as it is illegal to do this work for you, it needs to be done for the owner of the building.