Wiring 12/3 wire with only one open slot in breaker box?


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Old 12-31-14, 01:08 PM
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Wiring 12/3 wire with only one open slot in breaker box?

Hi Guys...trying to figure out some stuff on how to wire my mini split a/c system.

So I opened up the breaker box, and only have 1 open slot, and I need to wire a 230v connection to my minisplit a/c system. I think I've got a few options, but wasn't sure which was best.

1) I already have a 15amp line that runs back there that went to an old above ground pool that used to be back there. It's not currently in use, but I think uses the standard 'marco' or 14/2 line? I'd like to keep that line and connect it to my shed on that side of the house, a 300 watt outdoor landscape transformer, and maybe like 3 outlets that would never be under any serious load. BUT...I don't think I could wire the 230 - 20amp circuit for the a/c since my breaker box only has one open slot for the 12/3 wire?

2) I currently have a 50amp gfci circuit run in my garage (it's for my home brewery that never pulls more than 24 amps). I 'think' I could extend that circuit with the 12/3 wire to the back A/C unit. There I could simply exchange the on/off box for a 20amp 'sub-breaker' box, and wire up the A/C unit? That way I could use the 15amp line that's already been run back there for other stuff. I think I prefer this option. Will something like that work? The thing is I got the GFCi to protect me from shocking the crap out of myself. Does the 12/3 wire have a neutral wire included to extend it to the other box? Would that mess up the neutral signal to the GFCI if I extended it to a sub panel if the A/C unit has no need for a neutral line?

3) My third option which I really don't like is to just pull the old 15amp circuit, and use that with the open slot and wire the 12/3 wire directly into the box. I don't really want to do that unless that's my only option because I really could use that other 15amp circuit that's already been run back there.

Thanks for any tips guys.
 
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Old 12-31-14, 02:28 PM
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I currently have a 50amp gfci circuit run in my garage (it's for my home brewery that never pulls more than 24 amps).
Sound like a code violation if this is a detached garage and you have a separate circuit for lights. Lets clear this up first and go from there. If this is a detached garage you could install a subpanel and use that to power shed and yard lights and get rid of the unused 15 amp circuit to free up space for the new 240 (not 230) breaker.
 
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Old 01-01-15, 09:43 AM
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The garage is attached and has 2 circuits - the one is a 15amp service which constantly pops that powers the sockets and the opener. The other is the 50amp gfci circuit that runs under the stairs in my garage to a single outlet I use to power my homebrew setup.
 
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Old 01-01-15, 10:28 AM
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Tell us about the main panel, is it 100 amp, 125 amp, 200 amp? Will the main panel accept tandem breakers? Do you have a catalog number of the panel?

Another possibility, are there any lightly loaded single pole circuits that could be combined to free up a space?
 
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Old 01-01-15, 10:32 AM
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It's a 200amp panel, and yes, it will accept tandem breakers - the 50a gfci is a tandem breaker. On the lower left is where the 20amp circuit runs that fed the pool that isn't in use - but as I mentioned before it's a 14-2 cable (I believe...I know it only has 3 wires total). Directly below that is the saddle that's not in use. The white breaker is the 50amp gfci that feeds an 8 or 6 gauge 3 core + 1 ground wire. Here's a picture:

 
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Old 01-01-15, 10:58 AM
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It's a 200amp panel, and yes, it will accept tandem breakers - the 50a gfci is a tandem breaker.
No, the 50A GFCI breaker is a 2-pole breaker, not a tandem breaker. I do, however, see you have some tandem breakers with the blue handles. A tandem breaker provides two single pole circuits in one space. With some rearrangement of the breakers and adding a couple single pole tandem breakers, you could free up enough space for what you want to do. It's a Bryant panel and appears to be a 20-40 panel. Use Cutler-Hammer BR series tandem breakers. I believe the correct catalog number would be BD2020 or BD1515, but I am not 100% certain. Regardless, use CTL tandem breakers.
 
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Old 01-01-15, 11:47 AM
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Ah! I see exactly what you're talking about! Quick question:

The 20amp lower left line is the old pool circuit. The tandem breaker on the lower right doesn't have a line run to it. Should I just switch that 20amp pool line (the pool is gone, so it's not in use, I was planning on using it for 3 outlets that won't see a heavy load and an outdoor landscaping 300w transformer) to the 4th blue tandem breaker on the right side, and then just get a single 20amp breaker for the last slot on the left, and then run the one red wire and one black wire from the 12/3 to each of the 20amp single pole breakers on the left (So I'd need to purchase one red single pole breaker)? The air conditioner needs a 20 amp breaker total...so I'm not sure how that might affect it?
 
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Old 01-01-15, 12:09 PM
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No. Your A/C requires a 2 pole 20 amp breaker, not two single poles. You will need two spaces adjacent to each other.
 
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Old 01-01-15, 12:29 PM
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Ah I got you. Sounds good.
 
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Old 01-01-15, 07:39 PM
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The 20amp lower left line is the old pool circuit. The tandem breaker on the lower right doesn't have a line run to it. Should I just switch that 20amp pool line (the pool is gone, so it's not in use, I was planning on using it for 3 outlets that won't see a heavy load and an outdoor landscaping 300w transformer) to the 4th blue tandem breaker on the right side
That will work. I believe the blue handled breakers are 15A.

Then, like Tolyn said, put a 2-pole 20 amp breaker at the lower left 2 spaces. I believe the breaker you'll need is a Cutler-Hammer BR220.
 
 

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