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Running 220 for a new A/C unit - what guage wiring should I use?

72K views 34 replies 15 participants last post by  Mike Finley 
#1 · (Edited)
I'm working on an addition to my house.
At the same time, I plan on installing central heat and air.

I've already run 12 & 14 guage wiring for my lights and outlets.
What guage wiring should I run for the HVAC if it needs 220?
Also, circuit breaker capacity?
 
#3 ·
Above what Mike said - if you're pulling wire more than 140 feet or so I would suggest upsizing that wire to #4. Or change to copper wire. It's not likely that you will need to pull further than that - just something to think about. The a/c unit will tell you what you need for amperage. Mine needed 60amps. Not only a disconnect box but a disconnect box with a fusible link. The type of fusible link will be determined by the a/c unit recommendations(continual use or single use).
 
#5 ·
On a side note, I gave up 14 gauge wire long ago for my own residences or projects. 20 amp circuits with 12/2 is the only thing I put in now. The difference in cost is minimal, the labors the same, but the benefits are huge. I predict 15 amp circuits will follow the path of the fuse.
 
G
#8 ·
Most residental units are single phase. Depending on the size of the equipment and what the length of the run is will determine the wire size. A disconnect is required per code. At least here in florida. The disconnect must be within reach of the condensor.If the condensor is single phase then you only need to run 6/2 stranded with ground. No need to spend the extra $$$$ on the 6/3 when you only need 2 legs and a ground.
 
G
#9 ·
Just a thought.

Forgive me if i'm wrong, but I always run the size wiring depending on how many amp sevice the "outdoor unit" will need. Of course you can run larger wiring, but not very cost conservative. If you're building an addition, the size of the addition will determine the size of the unit to use. If I was spending all that money on a project I'd want to save money where I could. Never seems like much in the beginning, but a dollar here and a dollar there does add up at the end. The odds of needing larger wiring for a unit like this in the future is not likely, cause the one you installed should be the one called for on your project. The odds of changing it in the future isn't very likely. Just do your research, decide if the ton usage is ideal for your space. Then decide if the unit you're installing is the right one for you.
 
#12 ·
As I read through this thread I was wondering when someone was going to ask the amperage. I also wondered where the first replier came up with 50 amps/6 wire with the only spec being given was 220 volts.

I am on the other side when it comes to 14 wire/15 amp circuits. Why do you guys hate them so? There is absolutely no way anyone can tell me that using #12 is safer, which I do get from time to time. Properly sized and logically loaded circuits are safe no matter what guage/breaker size.
You obviously don't do many multi gang boxes with dimmers or 4 ways very often. If I was told I had to do all my residential lighting wiring in #12 I would refuse the job. The thought of a 4 gang box with 3 dimmers and a 4-way in there (very common), in all #12 is frightening.
Is box fill an issue for you as well. I sometimes get close to full with 14 in switch boxes. With 12 it would be out of the question.
You all must love carrying around those 120 pound 1000' spools of 12/3.:cheesygri:eek:
 
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#13 ·
Speedy Petey said:
As I read through this thread I was wondering when someone was going to ask the amperage. I also wondered where the first replier came up with 50 amps/6 wire with the only spec being given was 220 volts.

I am on the other side when it comes to 14 wire/15 amp circuits. Why do you guys hate them so? There is absolutely no way anyone can tell me that using #12 is safer, which I do get from time to time. Properly sized and logically loaded circuits are safe no matter what guage/breaker size.
You obviously don't do many multi gang boxes with dimmers or 4 ways very often. If I was told I had to do all my residential lighting wiring in #12 I would refuse the job. The thought of a 4 gang box with 3 dimmers and a 4-way in there (very common), in all #12 is frightening.
Is box fill an issue for you as well. I sometimes get close to full with 14 in switch boxes. With 12 it would be out of the question.
You all must love carrying around those 120 pound 1000' spools of 12/3.:cheesygri:eek:
Hmmmmm I didnt realize there were still ppl still using #14. Never really thought of it helping out with boxfill though. Actually I have never used #14. It is just easier for me to put everything on #12. Just stick up one reel of wire and use it till it empties. The 4 and 5 gangs are a pain though but I just try to dead end as much as possible on those.
 
#14 ·
I've been told by my inspector that I need to terminate the wire in a j-box just before I poke out through the stucco (I haven't stucco'd yet, only lathed.)
Th inspector wants some sort of lathe ring for the water-proof conduit coming out.

What does this ring look like, where can I find one? Home Depot, Lowes, and Ganahl lumber have no clue what I'm talking about. It seems that only the inspector knows.
 
#16 ·
you should use a 60 amp dissconnect for your a/c unit.. NOT a 50 it has a bigger possibility of tripping more often when the heat is kicked on, and it will cause you hassel and you will end up wanting a 60 amp breaker you will have wasted the money on the 50 amp... do not use a 50 amp!
 
#19 ·
Everybody is an electrician but me

Why can't electricians answer electrical questions, plumbers plumbing questions and so on? If you do not know what you are talking then just read the posts and move on. You guys crack me up , I run across this all the time, guys in different trades always giving advice and telling you that they know all about your work, and believing they know what they are talking about!
 
#20 ·
raab420 said:
you should use a 60 amp dissconnect for your a/c unit.. NOT a 50 it has a bigger possibility of tripping more often when the heat is kicked on, and it will cause you hassel and you will end up wanting a 60 amp breaker you will have wasted the money on the 50 amp... do not use a 50 amp!
Why not a million amp...then it will never trip.;)
 
#21 · (Edited)
Hey BIGRED this is "contractor talk" where you can ask a painter, or better yet a residential builder how to wire your HVAC unit. So why don't some of you tell the original poster what the inspector wants for the stucco thingy. Hell anybody can tell him to use #6 wire when you don't have a clue as to what the unit requires. The simple correct answer would be to look at the specs on the unit and comply with them. If you dont understand them, contact an electrician. It would be much safer and may even be cheaper than if you pull #6 wire where #12 is required. Just my opinion, as I am an electrical contractor and don't know too much about it either. What we need is a sharp home inspector to tell us what we need to do here. There are some sharp home inspectors out there, there has got to be.
 
#23 ·
I can understand the point about running a #6 without knowing the specs. What would make it cheaper is when you didn't have to pull it out and re-run it since you ran what is considered about the biggest a residential unit would be.
But without knowing the specs to say "Use a 60a breaker since a 50a will trip" is ridiculous.

At the same time is whole heartedly agree with RED.
 
#26 ·
BIG
You would run #6 because someone here, one of the self proclaimed experts, told you to. If you followed that advice when the unit only required #12 it could cost more than if a qualified person did the installation for you. The title line says A/C unit. That must be a large A/C unit to require #6.
 
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