Air conditioning power requirements ... question-
I'm trying to get my terminology right when explaining power requirements of central air systems.
I know, say, a two ton condenser needs 208 V [with a 25 amp HACR breaker]. The breaker typically connects with both legs of a breaker panel.
1] This is 208 single phase?
2] How about a fan coil? Are some 120V and others 208?
3] Are both residential 120V and 208V single phase?
4] Do some codes require a neutral AND a ground for a 208/220 component?
5] Why do some people say 208, and others say 220? Are they just about the same?
6] If you are running a condenser with [12 gauge] two hots and a ground, is this 12-2, or 12-3? I always thought you didn't count the bare copper wire. I've bought plenty of 12-2 for rewiring my house, but an installer called the same wire 12-3, when he wanted to use it to supply two hots and a neutral [he was not using a separate ground]. *note: When hooking up coffee machines at a union-run convention center, the union required the 220V Bunn to have two hots, a neutral, and a ground.
Thanks! If you can answer all six, you get a pat on the back!
I know, say, a two ton condenser needs 208 V [with a 25 amp HACR breaker]. The breaker typically connects with both legs of a breaker panel.
1] This is 208 single phase?
2] How about a fan coil? Are some 120V and others 208?
3] Are both residential 120V and 208V single phase?
4] Do some codes require a neutral AND a ground for a 208/220 component?
5] Why do some people say 208, and others say 220? Are they just about the same?
6] If you are running a condenser with [12 gauge] two hots and a ground, is this 12-2, or 12-3? I always thought you didn't count the bare copper wire. I've bought plenty of 12-2 for rewiring my house, but an installer called the same wire 12-3, when he wanted to use it to supply two hots and a neutral [he was not using a separate ground]. *note: When hooking up coffee machines at a union-run convention center, the union required the 220V Bunn to have two hots, a neutral, and a ground.
Thanks! If you can answer all six, you get a pat on the back!
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if I can admit to not knowing what any of the six are about, do I get a pat on the rump? 0 -
208 is normaly a 3 phase voltage, residential "standard" voltages are normaly 110/220, 115/230 & 120/240 (your appliances will work on any of the 3).
In single phase power the 2 legs are 180deg apart, in 3 phase the legs are normaly 120deg apart (in a couple of different layouts, Delta and Star).
Making the assumption that you mean that the higher voltage is 2x the lower number
1= yes
2= 110 or 24vac to drive the relay coils (small transformer inside the unit)
3= yes
4= yes
5= see opening comments, IOW they don't know any better
6= 12-2 is black, white, and bare, 12-3 is black, white, red and bare. The proper name is 12-x with ground. The electrician was using the bare as the neutral/ground combined. It works, but it's not a good practice.
Not a liscensed sparky, just a machine builder & maintinance supervisor0 -
Thanks for clearing that up.
Got it .. the 180 vs 120 just came together.
I'm exposed to a lot of people who have had a vauge understanding of electricity their entire installation career, even over five decades. And I've never taking the time [until now] to ask the right person.0 -
The "electrician" that uses an uninsulated ground wire as the neutral is not doing you any favors. Will it work? Yeah. Can it kill you? Yeah. Burn your place down? Yeah. Hey, 3 for 3! 0 -
Just noted that you said 12ga wire with a 25amp 2 pole breaker, not a good plan.
12ga wire and no larger than a 20amp breaker, for a 25amp breaker you want at least 10ga wire installed.
Personaly I wouldn't be running romax type wire to a 220v AC unit, I'd lay conduit (most likely PVC) and pull in 4 pieces of 10ga stranded wire (MTW, Machine Tool Wire), 2 black, 1 white and 1 green.0
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