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Old 05-13-2013, 02:32 PM   #1
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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?

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Old 05-13-2013, 02:45 PM   #2
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10/2 air conditioner wiring - clarification


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

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Old 05-13-2013, 02:47 PM   #3
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10/2 air conditioner wiring - clarification


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 .
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Old 05-13-2013, 03:13 PM   #4
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10/2 air conditioner wiring - clarification


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
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Old 05-13-2013, 04:14 PM   #5
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10/2 air conditioner wiring - clarification


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Originally Posted by fdmillion View Post
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.




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Originally Posted by fdmillion View Post
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.
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Old 05-13-2013, 05:00 PM   #6
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10/2 air conditioner wiring - clarification


You may not even need #10. Check the nameplate for the minimum circuit ampacity. You might only need #14.
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Old 05-13-2013, 07:17 PM   #7
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10/2 air conditioner wiring - clarification


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Originally Posted by Speedy Petey View Post
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.
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Old 05-13-2013, 08:57 PM   #8
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10/2 air conditioner wiring - clarification


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.
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Old 05-13-2013, 09:36 PM   #9
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10/2 air conditioner wiring - clarification


Perhaps the licensed electrician will know?
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Old 05-13-2013, 10:10 PM   #10
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10/2 air conditioner wiring - clarification


An overly simplified version is the current from one leg returns on the other leg.
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Old 05-13-2013, 11:55 PM   #11
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10/2 air conditioner wiring - clarification


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
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Old 05-14-2013, 05:35 AM   #12
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10/2 air conditioner wiring - clarification


Quote:
Originally Posted by Jim Port View Post
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
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Old 05-14-2013, 06:17 AM   #13
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10/2 air conditioner wiring - clarification


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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.
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Old 05-14-2013, 07:02 AM   #14
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10/2 air conditioner wiring - clarification


Quote:
Originally Posted by Speedy Petey View Post
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.
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Old 05-14-2013, 07:37 AM   #15
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10/2 air conditioner wiring - clarification


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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