Replace 20 amp breaker with 25 amp breaker
#1
07-17-15, 06:11 PM
Replace 20 amp breaker with 25 amp breaker
Hi all-
Long story short, I have a 20 amp dual pole breaker with 12 gauge wire for central air currently. The a/c unit needs 25 amp. Had a guy out to service the a/c and he was the one who told be that it needed to be 25. He was going to swap out the 20 with a 30 amp until he noticed it was 12 gauge wire. He said he didn't want to run the risk of starting a fire, but that I could go buy a 25 amp and replace it myself no problem. Is this true?
Long story short, I have a 20 amp dual pole breaker with 12 gauge wire for central air currently. The a/c unit needs 25 amp. Had a guy out to service the a/c and he was the one who told be that it needed to be 25. He was going to swap out the 20 with a 30 amp until he noticed it was 12 gauge wire. He said he didn't want to run the risk of starting a fire, but that I could go buy a 25 amp and replace it myself no problem. Is this true?
#2
07-17-15, 06:32 PM
Wire Capacity Chart
According to a chart on that site, the answer is 23 amps, so I suppose it's close enough. Wait for other answers.
According to a chart on that site, the answer is 23 amps, so I suppose it's close enough. Wait for other answers.
#3
07-17-15, 07:10 PM
Member
Yes, you can upsize the CB only on dedicated motor circuits, like your a/c. 25A is fine on 12AWG. You may see the mark HACR on the breaker; this means it has a time delay characteristic to accommodate high inrush motor currents, esp. compressors.
#4
07-17-15, 07:39 PM
Group Moderator
Hopefully it is a short run between your panel and the condenser. A long piece of #12 will have a lot of voltage sag/drop on compressor startup.
#6
07-18-15, 06:46 AM
Member
If the unit is existing and the 20 amp breaker isn't tripping I'd just leave it alone. If this is a new unit, check the data plate for the Minimum Circuit Ampacity (MCA). If it is 20 amps or less, the #12 wire is fine. Then check the Maximum Overcurrent Protection (MOCP) or Max Fuse Size. If it says 25 amps or higher you can change the breaker to 25 amps.
#7
07-18-15, 07:03 AM
The unit is not new, it's from 2004. A/C tech said the unit needs a 25 amp. I think they just never changed, or upgraded breaker, when they replaced unit. It is tripping. Did it a couple times earlier this year, now more frequent. I guess the compressor is starting to go and when it is starting up it sometimes throws the breaker. He put a hard start kit on the a/c and it hasn't tripped yet, but with a 25 amp it would trip less often because of the spikes when turning on.
#9
07-18-15, 05:52 PM
Member
The unit is not new, it's from 2004. A/C tech said the unit needs a 25 amp.
#12
07-18-15, 06:29 PM
Member
25 amps was never considered a standard circuit breaker size and was always available on special order only till the last several years. Since A-C units have gotten so much more efficient and the required amperage has dropped, so has the circuit protection. Now, most supply houses stock the 25 amp breakers. I believe the box stores have also started stocking some of them as well. In your case, I believe I'd use the 30 amp breaker.
#14
07-18-15, 06:42 PM
Member
So a 30 would be ok with 12 gauge wire?
#15
07-18-15, 07:04 PM
Ok cool. I thought the 25 amps was the MCA number. I looked at it again and it says "Minimum Supply Circuit Ampacity" 19 / 19 amp. That must be the number you are looking for.
