AC mini split wire size question

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Old 07-15-16, 06:28 PM
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AC mini split wire size question

I'm doing the wiring on a mini split AC unit. I thought it was going to be 15 amp breaker 120v with 14 awg so I went out and bought everything and ran it before the unit showed up but now I'm not so sure.

Below is whats on the plate of the outside unit:
fan motor load (Indoor/Outdoor) .3A / .7 A
Compressor load: 15 amp
minimum circuit ampacity 20 amp
Max fuse 30 amp.

I'm sure I need to swap out the 15 amp breaker with a 20 but do I need to run 12 awg instead of 14?

Thanks!
 
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Old 07-15-16, 06:32 PM
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Unfortunately yes. You'll need to replace the #14 with #12 and use a 20A breaker.

Just so you are aware..... most split units require a three wire cable plus ground between the condensor and the evaporator inside. The two wire feed goes to the outside unit.
 
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Old 07-15-16, 06:36 PM
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Crap...... Ah well.

Yes I've already got the control wire for the inside unit. It only required 16awg and I bought 14 because that was easier to find so I'm better than good there


Thanks for the fast reply PJ.
 
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Old 07-16-16, 07:01 AM
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Since it is an A/C unit with a stated MCA you may be legal to use 14 gauge wires with a 30 amp breaker. Don't know what the Canadian rules are. Give your inspector a call.

Mod Note: the minimum circuit ampacity calls for a 20 amp circuit. The #14 is too small.
 

Last edited by pcboss; 07-16-16 at 08:24 AM.
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Old 07-16-16, 06:05 PM
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You'll need to replace the #14 with #12 and use a 20A breaker.
Yes, the wiring needs to be replaced with #12, but I think I'd use a 30 amp breaker.

most split units require a three wire cable plus ground between the condensor and the evaporator inside.
Why would a 3 wire cable plus ground be needed for a 120 volt unit? I've never wired one of these and want to learn. Have been thinking of replacing a through-the-wall heat/A-C unit with one.
 
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Old 07-16-16, 08:06 PM
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The power goes to the condensor outside. The inside unit actually does the controlling.
The power goes inside on white and black and out on the red for the compressor.
 
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Old 07-16-16, 08:28 PM
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Mod Note: the minimum circuit ampacity calls for a 20 amp circuit. The #14 is too small.

Last edited by pcboss; Today at 11:24 AM.
OP is in Canada so I questioned whether different rules applied. Used to be OK here before 2009. CEC Table 2 shows 20 amp.
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