# 10/2 air conditioner wiring - clarification



## Huck2013 (Apr 23, 2013)

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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## mpoulton (Jul 23, 2009)

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


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## bobelectric (Mar 3, 2007)

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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## fdmillion (Jan 27, 2010)

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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## Speedy Petey (Feb 1, 2004)

fdmillion said:


> 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. 






fdmillion said:


> 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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## Jim Port (Sep 21, 2007)

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


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## usair (May 6, 2013)

Speedy Petey said:


> 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.
> 
> 
> 
> ...


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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## Jim Port (Sep 21, 2007)

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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## sirsparksalot (Oct 16, 2010)

Perhaps the licensed electrician will know?


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## Jim Port (Sep 21, 2007)

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


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## frenchelectrican (Apr 12, 2006)

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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## Philly Master (Mar 30, 2013)

Jim Port said:


> 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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## Speedy Petey (Feb 1, 2004)

Philly Master said:


> 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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## usair (May 6, 2013)

Speedy Petey said:


> 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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## Huck2013 (Apr 23, 2013)

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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## beenthere (Oct 11, 2008)

usair said:


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



York TCGF18S41S3 Min over current device amps 15, max over current device amps 20.

The 2, 2.5 and 3 ton in that model line has a min amp device of 20. the 3.5 has a min amp of 25. The 4 ton is min 30, and the 5 ton is min 40.


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## mm11 (Apr 30, 2013)

usair said:


> 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.


Any location outside, even in raceway, requires the use of conductors rated for wet locations. Using THHN would be a violation if installed outside.


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## electures (Dec 22, 2009)

mm11 said:


> Any location outside, even in raceway, requires the use of conductors rated for wet locations. Using THHN would be a violation if installed outside.


THHN is dual rated THHN/TH*W*N.


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## mm11 (Apr 30, 2013)

electures said:


> THHN is dual rated THHN/TH*W*N.


Using THHN outside is a violation. It's rated for dry and damp locations only, as I'm sure you know. The comment I responded to had no reference to multi-rated wire, such as MTW/THWN-2/THHN, which *is* acceptable to use outdoors.


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## busman (Nov 7, 2008)

electures said:


> THHN is dual rated THHN/TH*W*N.


Not if it doesn't say THWN.

Mark


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## electures (Dec 22, 2009)

busman said:


> Not if it doesn't say THWN.
> 
> Mark


And how often do you see straight THHN? Almost never.


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## usair (May 6, 2013)

mm11 said:


> Using THHN outside is a violation. It's rated for dry and damp locations only, as I'm sure you know. The comment I responded to had no reference to multi-rated wire, such as MTW/THWN-2/THHN, which *is* acceptable to use outdoors.


 Oooops I forgot this is a forum and I should have been VERY clear :laughing: we dont buy THHN that is not dual rated as a matter of fact I am not sure if it is available without a special order. Next time I will be sure and post DUAL rated THHN must be in conduit. :whistling2:


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## Speedy Petey (Feb 1, 2004)

mm11 said:


> Any location outside, even in raceway, requires the use of conductors rated for wet locations.


Not true. Not all outdoor raceways are wet locations.

All _underground_ outdoor raceways are though.


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## Speedy Petey (Feb 1, 2004)

busman said:


> Not if it doesn't say THWN.
> 
> Mark


I'll ask the same thing. When was the alst time you bought new THHN that was not dual rated with THWN??

It is so petty when folks just HAVE to point this out when it is a complete non-issue.


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## Huck2013 (Apr 23, 2013)

I've only been on this forum for a few weeks. I came to get reasonable answers/ideas from reasonable people. However, this forum seems more of a school yard mentality (my dad's better than your dad). 

Anyone know a forum where I don't have to filter though all this bs?


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## Speedy Petey (Feb 1, 2004)

Huck2013 said:


> I've only been on this forum for a few weeks. I came to get reasonable answers/ideas from reasonable people. However, this forum seems more of a school yard mentality (my dad's better than your dad).
> 
> Anyone know a forum where I don't have to filter though all this bs?


Might I suggest you get a thicker skin or possibly be less picky?
I don't know what thread you are reading but in this one all I see is adult discussions about technical issues. 
Can you point out the _"my dad's better than your dad"_ stuff you are talking about?


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## electures (Dec 22, 2009)

That's it. I'm getting the popcorn.


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## Philly Master (Mar 30, 2013)

Huck2013 said:


> I've only been on this forum for a few weeks. I came to get reasonable answers/ideas from reasonable people. However, this forum seems more of a school yard mentality (my dad's better than your dad).
> 
> Anyone know a forum where I don't have to filter though all this bs?


 what question do you have that was not answered ?? 


but .. here ..


120 v is 1 hot to 1 neutral ....

240 is 2 hots .. no nuetral needed in its purest form ... ( so 10/2) would be fine ..

some things need the neutral wire to run the lower voltage (120v ) stuff so 10/3 is used ie your dryer and your stove, the cotrols, timers, clocks, etc are 120 v


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## busman (Nov 7, 2008)

Speedy Petey said:


> I'll ask the same thing. When was the alst time you bought new THHN that was not dual rated with THWN??
> 
> It is so petty when folks just HAVE to point this out when it is a complete non-issue.


Well, we'll just have to agree to disagree. I'm sure somewhere in the US, there are still spools of THHN that is not labeled as THWN. I agree that this is a non-issue for professionals for two reasons:

1) We mostly only use newly purchased materials and probably don't have a spool of wire that is more than a few years old.

2) We know better.

My post was directed at the DIY, who is more likely to try to re-use materials. How many times on this forum have we heard things like "Is there a way I can use this wire, it's what I already have?" I just wanted to be clear that people need to read the markings on their wires to know that can be used for.

Mark


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## mm11 (Apr 30, 2013)

Speedy Petey said:


> Not true. Not all outdoor raceways are wet locations.
> 
> All _underground_ outdoor raceways are though.


If the raceway is exposed to weather, it's a wet location. I can't think of a raceway I've ever run outside that wasn't exposed to weather for at least some portion of the run.


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## Philly Master (Mar 30, 2013)

mm11 said:


> If the raceway is exposed to weather, it's a wet location. I can't think of a raceway I've ever run outside that wasn't exposed to weather for at least some portion of the run.



*DAMP* or WET ??

artical 100


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## Philly Master (Mar 30, 2013)

Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.

Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.

Location, Wet. Installations under ground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.


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## mm11 (Apr 30, 2013)

What's your point Philly? 

Exposed to weather= wet location


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## Speedy Petey (Feb 1, 2004)

mm11 said:


> Exposed to weather= wet location


So if the outside of the conduit is "exposed to weather" that make the inside a wet location? 
Where can I find this in the code book? I am curious.


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## mm11 (Apr 30, 2013)

speedy petey said:


> so if the outside of the conduit is "exposed to weather" that make the inside a wet location?
> Where can i find this in the code book? I am curious.


300.9


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## Philly Master (Mar 30, 2013)

mm11 said:


> What's your point Philly?
> 
> Exposed to weather= wet location


Not wet ....unless its buried...


Take a 3R panel. Is it Waterproof ? NO......But u can use it outside all by its self, and only protects from rain etc ..but a 
4, 4X is different




http://en.wikipedia.org/wiki/NEMA_enclosure_types


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## sirsparksalot (Oct 16, 2010)

Speedy Petey said:


> So if the outside of the conduit is "exposed to weather" that make the inside a wet location?
> Where can I find this in the code book? I am curious.


I can't give the citation, but every time someone asks about NM ran in conduit underground, everyone says the conduit is considered a wet location

:no:


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## Philly Master (Mar 30, 2013)

sirsparksalot said:


> I can't give the citation, but every time someone asks about NM ran in conduit underground, everyone says the conduit is considered a wet location
> 
> :no:


I agree and mm11 has right code section...for buried stuff


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## sirsparksalot (Oct 16, 2010)

mm11 said:


> 300.9


Yep, and 300.5 (B) covers Underground locations as being wet.

Thanks, mm.


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## mm11 (Apr 30, 2013)

Philly Master said:


> Not wet ....unless its buried...
> 
> 
> Take a 3R panel. Is it Waterproof ? NO......But u can use it outside all by its self, and only protects from rain etc ..but a
> ...


Incorrect- refer to 300.9 and the definition of wet locations you posted earlier. 

You're posting about enclosures now, which is a tangent from the current discussion.










For example, the LFMC in this pic is installed in a wet location, and the interior of the raceway is also a wet location.


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## sirsparksalot (Oct 16, 2010)

Philly Master said:


> I agree and mm11 has right code section...for buried stuff


310.9, yes, above grade wet location


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## Philly Master (Mar 30, 2013)

310.8 ...... .'??? 2008


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## mm11 (Apr 30, 2013)

Philly Master said:


> 310.8 ...... .'??? 2008


Philly, I don't have my 2008 codebook with me. All my sections were from the 2011 edition. There is no 310.8 in 2011, so I'm not sure what you're referencing.


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## Philly Master (Mar 30, 2013)

We are 2008 up here in philly area.... Was added in 2008


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## Speedy Petey (Feb 1, 2004)

mm11 said:


> 300.9


Thank you. I had forgotten about that section. I was thinking of 300.5.


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## beenthere (Oct 11, 2008)

Question asked, question answered. Thread going no where, thread closed.


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