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Huck2013 05-13-2013 03:32 PM

10/2 air conditioner wiring - clarification
 
Hello All,

I have a licenced electrician coming in the house to install a new Central Air Unit. The material are currently in my garage and I see he's using 10/2 wire and a double pole breaker.

I "know" both wires in the 10/2 are hot/lead wires, but conceptually I can't wrap my head around it.....is there no neutral?

mpoulton 05-13-2013 03:45 PM

No neutral. The air conditioner is 240V-only. A neutral is only needed for a 120V or 120/240V load.

bobelectric 05-13-2013 03:47 PM

No neutral. 2 hots and a ground. Make sure there is a sevice gfi receptacle nearby.And nm cable isn't allowed to be used in wet locations .

fdmillion 05-13-2013 04:13 PM

10/2 is acceptable for a single-appliance circuit where the appliance needs ONLY 220v. Central air compressors would usually fall in this category.

You'd need 3 wire cable (with a neutral) for appliances where an appliance may require dual voltages. Examples might be a range, where 110 is used for the lights/timer/clock/etc and 220 is used for the heating element; another would be a clothes dryer where the tumbler motor runs on 110 but the heater runs on 220.

3 wire cable is also used for subpanel installation, e.g. to a garage, because your subpanel needs a neutral.

In short, a neutral is needed in any situation where the destination might need 110 for any reason. For your AC unit, there shouldn't be a reason for it to need 110v, so feeding the 220v circuit without a neutral works fine. Remember, voltage across the two hots is 220v, and voltage from either hot to neutral is 110v, this is how we can have dual voltages.

(Note that when I say 3 wire cable, I mean 3 wire + ground. Same for 2-wire cable - 10/2 cable should contain two 10 gauge hots plus a ground. You NEED a ground on any new installation, I don't believe there are are any common exceptions to that.)

As suggested before, just make sure all other codes are complied with. You need a GFCI outlet, but AFAIK it can run off a separate circuit (in my house the GFCI outdoor outlet by the AC unit runs off my furnace's circuit while the AC has a dedicated circuit.) Also make sure you follow any codes for cable that goes outdoors (if I recall right, it needs to be armored and/or in conduit)

F

Speedy Petey 05-13-2013 05:14 PM

Quote:

Originally Posted by fdmillion (Post 1178503)
10/2 is acceptable for a single-appliance circuit where the appliance needs ONLY 220v. Central air compressors would usually fall in this category.

I'm not sure what you mean by "a single-appliance circuit". 10/2 can be used for ANY straight 240V circuit 30A or less.




Quote:

Originally Posted by fdmillion (Post 1178503)
Also make sure you follow any codes for cable that goes outdoors (if I recall right, it needs to be armored and/or in conduit)

No such code like that that I know of.

Jim Port 05-13-2013 06:00 PM

You may not even need #10. Check the nameplate for the minimum circuit ampacity. You might only need #14.

usair 05-13-2013 08:17 PM

Quote:

Originally Posted by Speedy Petey (Post 1178562)
I'm not sure what you mean by "a single-appliance circuit". 10/2 can be used for ANY straight 240V circuit 30A or less.




No such code like that that I know of.

several "codes" I can think of.

NM cannot be used outdoors even in conduit thhn will neeed to be ran in conduit if used. UF can be used without conduit if allowed by local jurisdiction.

Jim Port 05-13-2013 09:57 PM

Neither armored cable or conduit is required outside by the NEC.

Bringing the NM into the back of the disconnect should be fine. NM cannot be used from the disconnect to the unit.

sirsparksalot 05-13-2013 10:36 PM

Perhaps the licensed electrician will know?

Jim Port 05-13-2013 11:10 PM

An overly simplified version is the current from one leg returns on the other leg.

frenchelectrican 05-14-2013 12:55 AM

I did noticed the OP is from Canada the rules should be simauir to the NEC is.

But for sure I know Joed is from Canada and he can reply this question related to the CEC codes.

Merci,
Marc

Philly Master 05-14-2013 06:35 AM

Quote:

Originally Posted by Jim Port (Post 1178598)
You may not even need #10. Check the nameplate for the minimum circuit ampacity. You might only need #14.

unless its a mini split ..... I personally have not seen any here less than 30 amps for the condenser

Speedy Petey 05-14-2013 07:17 AM

Quote:

Originally Posted by Philly Master (Post 1178973)
unless its a mini split ..... I personally have not seen any here less than 30 amps for the condenser

Mini-splits?? Really?

The last one I did was a single head that required only a 15A circuit. In fact the max OCPD was 15A.
Many/most I do are a 20A circuit. Even the multi-head ones.

usair 05-14-2013 08:02 AM

Quote:

Originally Posted by Speedy Petey (Post 1178996)
Mini-splits?? Really?

The last one I did was a single head that required only a 15A circuit. In fact the max OCPD was 15A.
Many/most I do are a 20A circuit. Even the multi-head ones.

I have never found one that needed less than a 30 could you give the model that takes a 15.

Huck2013 05-14-2013 08:37 AM

Thanks all for helping me wrap my head around the 10/2 wire and no neutral wire needed. As far as codes and other comments made; that is up to the electrician and beyond me.

cheers all.


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