Off topic electrical question.

[karl]

I realize this question doesn't have anything to do with wood heat, but since I know there are alot of tradesmen on the forum, I though I might get a quick answer.

My sister is renovating some property she bought. She had a Electrician/HVAC guy who is an idiot. I won't go into all the problems I've called him on so far, but calling him an idiot might be giving him too much credit.

Today he was hooking up the first outside AC unit. It's a standard 220 ton and half unit. He was wiring it with 12-2 wire. I told him that wouldn't work. He said it would. So I clarified, It will work but it's not up to code.

He is run one 110 leg through the black/hot wire; the second 110 leg through the white/common wire; and the bare wire goes to ground back at the circuit box. we got into an argument over the ground wire being the common. He said it doesn't have a common wire on it only a ground. I said your ground wire is acting as a common and you don't have a ground.

Can you guys please clarify this? And if you have time maybe post a link where I can get the information to print out for him. Or tell me he's right and I'm wrong.

Thanks.

 

[burntime]

I think mine is run with 10-3 on a 45-55 ft run and a 30 amp breaker for a 2 1/2 ton compressor if that helps. I know that at least in Wisconsin you also need a disconect with in so many feet of the unit.

 

[Ncountry]

I can not help clarify too much, but if he disconnects the ground, the ac unit would still operate. Even though I can wire a complete house, electricity still has a bit of mystery to me. All you "need" to run a 220 appliance or tool is a 110 line from both sides of panel box. I always guessed that maybe due to the alternating current the other leg acted like a neutral. Maybe an electrician will post the right reason??

 

[nshif]

Many 240V Items have no neutral connection. its quite common to have no neutral. As far as the wire gauge if the unit draws 20 amps or less all it needs is 12 Awg If its mgreater then 20 Amps then it needs to be larger. Using the white wire as the second hot is fine as long as its taped red at both ends, same as using the white on a 3 way lite taped black.

 

[Highbeam]

There are two common ways to wire 220 volt appliances. Some use 4 wires and some use only 3. If the appliance is strictly 220 as in a good old arc welder or wall heater then it will only need 3 wires 2 hots and one GROUND. If you find that the appliance needs 4 wires as most modern dryers, ranges, or hot tubs then you need all 4. 2 hots, one neutral, and one ground. Many appliances such as a range will use the neutral to internally run some motors or controls on 110 by using one of the hots and the neutral.

The real question is what does your specific model of heat pump require. If 4 wires come out of the heat pump then I would insist on 4 wires all the way to the panel.

Also, when you buy 12-2 and use it for 220 service then you will use a black to one hot leg and a white to the second hot leg. You must mark the white hot leg in the panel so that some poor fool doesn't mistake it for a neutral and try and run your heat pump on 110. The last wire, bare, goes to the ground bar and not the common bar.

I have at least half dozen 220 volt circuits in my panel run on 12-2 and it passed inspection this spring. These are for wall heaters and are only good for 20 amps.

I ran a 50 amp welder circuit using 4 strands and capped the white wire at the plug since my welder only needs 3 and the white neutral is for future application. Maybe a subpanel.

 

[karl]

Hibeam you hit on exactly what I was thinking. Your heaters are fine because they 220v through out. The AC unit is not because it has some 110 circuits inside, like the fan.

Any more people care to way in?

 

[EatenByLimestone]

Did he clearly label the white?

Matt

 

[begreen]

If there are 120v components, it requires 4 wire unless there is an internal transformer that steps down to 120v (unlikely, but possible). What is the make and model number of the outdoor AC unit?

FWIW, our heatpump compressor unit is strictly 220v. I could have wired it with #12 NM, but chose #10 due to the closeness of load spec (18 amps peak) and length of the run.

 

[seige101]

99.99% of all ac units i have wired in my electrical career only require straight 220/240 volts.

The easiest way to find out in your particular installation is look at the name plate on the unit it self. If it says 120/240 it needs 4 wires (2 hots 1 neutral and 1 ground) If it only says 240 then it is installed correctly.

 

[burntime]

I could be wrong but I thought without a ground the breaker would not trip in the case of a short...just kinda weld itself until it stopped or burned. I think seige is right with the exception of the ground...

 

[Highbeam]

When Seige says "straight" 220 he means a three wire hookup with a ground and two hots. Without a chassis ground or ground wire connection, the heat pump chassis won't take much any current in the event of a short ciruit the chassis will be energized and could shock the bajeepers out of the dog when the dog takes a pee on the heat pump. The circuit breaker would trip if excess current flowed through the dog.

On BG's 18 amp load: you did the right thing to upsize that wire. The load is not supposed to be designed for 100% of the breaker. I am almost positive that it is either 75 or 80 % utilization of the breaker and then you need to go up. That 10 gauge is good for 30 amps and was wise.

 

[seige101]

Highbeam is right. I didn't mention a ground because that is required no matter the voltage of the unit.

Standard rule of thumb when sizing a branch circuit that would be in continues use or any large permanent appliance is to multiply the name plate amperage by 125% that is your circuit size rounded up to the next standard breaker/wire size.

Highbeam you are right again, not to utilize more than 80% of a circuit rating.

 

[Ravenvalor]

Hi Folks:
I am an electrical contractor who has been in the business for 22 years. I cannot remember the last time I needed a neutral for an A/C. All you usually need is 2 hots and 1 ground. As far as using #12, that sounds fine also. You see, the code allows you to reduce the size of your wire for A/C's. Where most 30amp circuits need to be #10, A/C's only have to be on #12. The reason is because of the great starting load of A/C compressors.

I hope this helps
Jim

 

[Redox]

Ditto on Highbeam and Ravenvalor's answers. I don't think I have ever seen an AC unit that needed a neutral, certainly not a modern unit. All components run on 240V and there shouldn't even be a neutral connection on the unit. The answer might be different if this were a 3 phase grounded delta system, but that hasn't been used in years. Make sure you stick with the mfrs max breaker size rating and make sure the breaker is marked HACR and you will be fine.

Chris