What size wire for a 230 volt 20 amp breaker?

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Erico

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This is a dedicated circuit for an 8,000 BTU wall a/c receptical.

I assumed it should be 12 gauge wire but was surprised to find 14 gauge wire when replacing the a/c receptical.

To add to my confusion, the receptical is wired with a black and white wire - white is the second hot (but not marked with tape). There is a dead red wire in the box. Why they didn't use the red instead (or tape the white ) is a mystery. Note: this is metallic cable not romex. The cable runs hardwood floor and joins two 14 gauge hots in a junction box. I haven't opened the panel to look at the wire sizing in the panel box yet.

Is this ok or is it something I need to address?
 

DonL

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Most 240V AC units will not run without a neutral. Because of controls normally run on 120V. Being a 8000 btu it may be running on 120V, And 12 gauge or bigger should be used.

If it is really 240V, It Sounds like they are using the Ground wire for the neutral. That will work, but is not safe.

At one time it may have been a 120V split feed, may still be feeding 120V lighting, or other outlets, Including that one.

It may not be as dedicated as you think. What voltage are you reading at the outlet ?

Why are you messing with it ? Is something broke ?


Wear your PPE while testing.


Good Luck.
 
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Erico

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I had to relocate a junction box that held some light switches as part of a remodel I'm doing in my kitchen.

The line for the ac traveled throug the junction box. There is no ground visible - the conduit and metallic cable is grounded in the basement. As such, there are no separate ground wires anywhere in the house.

I have the two hots from the 220 v 20 amp breaker isolated. I also have the line that runs under the floor to the ac isolated. I didn't test the receptical before I pulled it apart (it was cracked and not secured properly) so I intended the replace it anyway. I initially thought it might be only 120v (even though it was using a 240v receptical). I did check and test the ac unit outlet in the front of the house and it is wired the same way - black and white both hot on a 20amp breaker. No ground or nuetral.

This ac unit is ancient. The controls are manual and not digital.



Most 240V AC units will not run without a neutral. Because of controls normally run on 120V. Being a 8000 btu it may be running on 120V, And 12 gauge or bigger should be used.

If it is really 240V, It Sounds like they are using the Ground wire for the neutral. That will work, but is not safe.

At one time it may have been a 120V split feed, may still be feeding 120V lighting, or other outlets, Including that one.

It may not be as dedicated as you think. What voltage are you reading at the outlet ?

Why are you messing with it ? Is something broke ?


Wear your PPE while testing.


Good Luck.
 

DonL

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Let me try again.

What Voltage do you read with a volt meter at the outlet ?

What plug does it have ?

I can put a 240 volt plug on anything and run it on 120V. It will work, But it may not be correct.
 

Erico

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I'll check the amperage of the ac tomorrow.

Yes. That's what I thought - 20 amp requires 12 gauge. I thought maybe there was some rule that said it was ok based on the fact the line is dedicated - or some other rule I'm not aware of. I always prefer to keep it simple AND err on the side of caution.

I just don't understand why someone would attach 14 gauge wire to a 20 amp breaker.

what is the amperage of the unit, NOT the btu rating. 14 gauge wire should NOT be connected to anything greater than a 15 amp breaker.
 

Erico

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I haven't tested it but will tomorrow and get back to you tomorrow. I don't see how it can be less than 220 because it is wired to 2 hots from a 220 breaker.

I should have checked the voltage before I disconnected the receptical. I had the power off when I pulled the box apart and capped the wires. When I saw white and black I though, like you, it might just be 110. Then I saw how the other ac in the front of the house is wired and I realized someone used white as the hot and didn't mark it.

There are two 20 amp 220 breakers in the pan

Let me try again.

What Voltage do you read with a volt meter at the outlet ?

What plug does it have ?

I can put a 240 volt plug on anything and run it on 120V. It will work, But it may not be correct.
Let me try again.

What Voltage do you read with a volt meter at the outlet ?

What plug does it have ?

I can put a 240 volt plug on anything and run it on 120V. It will work, But it may not be correct.
 

Speedy Petey

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If it is really 240V, It Sounds like they are using the Ground wire for the neutral. That will work, but is not safe.
If it's really a straight 240V circuit for an A/C then there would be NO neutral at all. No need for one, nor any place to connect it.
 

Speedy Petey

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If they used a white for a hot and spared the red that is a violation. If the red is present then there is NO reason to use the white for a hot.

Also, the #14 on a 20A in this instance is definitely wrong. If it were a hard wired A/C condensor or unit then it would be quite possible, even likely, that #14 on a 20A would be fine. Feeding a wall receptacle not so much.
 

DonL

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If it's really a straight 240V circuit for an A/C then there would be NO neutral at all. No need for one, nor any place to connect it.

I agree.

But it should have a ground. In the U.S.A.
 
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Erico

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Trying to understand how this happened, I guess maybe I can assume someone figured since it was a dedicated outlet it would be ok to wire #14 to this 20 amp 220v breaker?



If they used a white for a hot and spared the red that is a violation. If the red is present then there is NO reason to use the white for a hot.

Also, the #14 on a 20A in this instance is definitely wrong. If it were a hard wired A/C condensor or unit then it would be quite possible, even likely, that #14 on a 20A would be fine. Feeding a wall receptacle not so much.
 

Speedy Petey

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Trying to understand how this happened, I guess maybe I can assume someone figured since it was a dedicated outlet it would be ok to wire #14 to this 20 amp 220v breaker?
Possibly, but an 8k BTU unit should be perfectly fine on a 15A circuit, even a 120V one. In fact, I am surprised you even have an 8k @ 240V.
 

JerryR

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Not sure I've ever seen an 8k BTU air conditioner that is 240v.

An 8k 120v would only draw about 8 Amps. At 240 volts it would be about 4 amps. Either way a 15 amp circuit shoul be sufficient.

Would like to know make and model of your unit.
 

Jadnashua

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If the unit really only needs 8A or so, switch the breaker to a 15A one and be done with it. It should have a ground, though.
 

Cacher_Chick

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There were no equipment grounding conductors before 1964, so if the house is older than that, it would be grandfathered.
 

DonL

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There were no equipment grounding conductors before 1964, so if the house is older than that, it would be grandfathered.


That may true, Until you start adding and modifying the original wiring.

New additions and mods need to be brought up to the new code.

The conduit should be good for ground if it is completely intact.
 

Erico

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Not sure I've ever seen an 8k BTU air conditioner that is 240v.

An 8k 120v would only draw about 8 Amps. At 240 volts it would be about 4 amps. Either way a 15 amp circuit shoul be sufficient.

Would like to know make and model of your unit.
image.jpg
K
 

Jadnashua

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Without a ground conductor and not rewiring that circuit, you could make it safer by replacing the CB with a GFCI breaker. If it is plugged in, you may be able to find a 230vac GFCI receptacle. Since the wiring is only 14g, it should not have anything bigger than a 15A CB on it. Be warned though, that if the thing is worn, they will sometimes trip a GFCI, but in reality, if it did, under the same conditions, it might save you from a nasty shock. A properly working unit should not trip one, and if it does, implies a fault, whether in the design, or as a result of wear.
 

Erico

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image.jpg
Without a ground conductor and not rewiring that circuit, you could make it safer by replacing the CB with a GFCI breaker. If it is plugged in, you may be able to find a 230vac GFCI receptacle. Since the wiring is only 14g, it should not have anything bigger than a 15A CB on it. Be warned though, that if the thing is worn, they will sometimes trip a GFCI, but in reality, if it did, under the same conditions, it might save you from a nasty shock. A properly working unit should not trip one, and if it does, implies a fault, whether in the design, or as a result of wear.
It should be grounded through the conduit and/or metallic cable.

How can I check for ground? I have a plug-in tester for standard recepticals but not the 240v ac receptical.

I've tested all the other outlets in the house and everything is grounded. These old places in chicago are usually a combination of conduit, really old black conduit and miles of metallic cable.

The metallic cable is not legal in Chicago yet there are tons of it in these old places.
 
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