# high leg for single phase 240



## Jlarson (Jun 28, 2009)

It's called a delta high leg service. One winding of the transformer is center tapped giving you 2 phases that are 120 volts to ground and 1 that is about 208 to ground. Between any 2 phases you should get 240 volts. 

If the oven doesn't have a neutral then you can use any 2 legs. I usually try to put straight 240 loads on either A and B or C and B, B being the normal position for the high leg usually to try to balance things better.


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## Jlarson (Jun 28, 2009)

Just cause I got one here's a graphic explaining it.


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## bobelectric (Feb 24, 2007)

For that connection in the panelboard,you must use a Delta rated circuit breaker.


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## Chris Kennedy (Nov 19, 2007)

bobelectric said:


> Delta rated circuit breaker.


You mean non-slash rated?


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## bobelectric (Feb 24, 2007)

I only did a few in my career,The panel door should list the acceptable breakers the panel can accept.


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## Southeast Power (Jan 18, 2009)

joe cool said:


> Can I safely use the high leg and one of the 120V legs to supply this oven? 120V slots in the panel are in very short supply.


That is exactly the way to do it.

Just for future reference,
You cannot use the high-leg to neutral for a "220 volt" connection. It is not intended for that.


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## Southeast Power (Jan 18, 2009)

bobelectric said:


> For that connection in the panelboard,you must use a Delta rated circuit breaker.


Is that like a wire stretcher?

I see that they are are all rated for 240. 

http://www.geindustrial.com/catalog/buylog/03_BL.pdf

I have seen a Delta breaker used in a single phase panel, but it doesn't relate to the OPs question.


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## Chris Kennedy (Nov 19, 2007)

jrannis said:


> I have seen a Delta breaker used in a single phase panel, but it doesn't relate to the OPs question.


Here is what the OP needs.




> 240.85 Applications.
> 
> A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1–3 to indicate such suitability.
> 
> A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker’s voltage rating.


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## Southeast Power (Jan 18, 2009)

Chris Kennedy said:


> Here is what the OP needs.


Thanks Chris,

GE TQB, THHQB, TQB, THHQL, TQL, THQL are OK in 3 phase but looking at the table on page 6, you would have to find a breaker with a "D" suffix if you are going with loadcenter type molded case breaker. 
Tough situation when the panel is short on spaces. Maybe it would be quick and easy to install a small loadcenter next to the existing one.


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## joe cool (Jun 4, 2009)

Thanks for the help.
It is an older QO type panel. It was late and I was making do with what was on the van so I used 2 single pole QO20's and handle tied them. If I replace those with a two pole 20/2 I should be good, right?
The correct oven hasn't arrived yet, the first one they got was 208V so I had them send it back. I wouldn't risk smoking their new oven to find out, but what do you think would happen if I connected the 208V oven to the high leg and neutral? (I'm not going to do this, just curious what you think would happen.)


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## micromind (Aug 11, 2007)

joe cool said:


> Thanks for the help.
> It is an older QO type panel. It was late and I was making do with what was on the van so I used 2 single pole QO20's and handle tied them. If I replace those with a two pole 20/2 I should be good, right?
> The correct oven hasn't arrived yet, the first one they got was 208V so I had them send it back. I wouldn't risk smoking their new oven to find out, but what do you think would happen if I connected the 208V oven to the high leg and neutral? (I'm not going to do this, just curious what you think would happen.)


It'd work just fine, you'd have close to 208. 

The problem is finding a single pole breaker rated at 208 (or higher). I've never seen one that'll fit a 120 panel. If a 277 volt breaker would fit the panel, you'd be fine. Except the 277 breaker likely wouldn't be listed for a 120 volt panel. 

Interesting to note, using the high leg to neutral is the only way a single phase load can be balanced across all 3 primary phases. 

Rob


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## danickstr (Mar 21, 2010)

regarding the 208 "custom" job: would it work fine because it is a resistive load? It seems like that wouldn't work with a motor, since you would only have "push" from one leg, right?


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## Shockdoc (Mar 4, 2010)

I have seen a few electricians run 220 window/wall A/C units off a sp breaker on the high leg. And some call me a hack......


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