# High leg



## Adam12 (May 28, 2008)

I have never personally worked on a high leg service and was wondering...
Is the stinger leg always 208v to ground or does it depend on how the XFMR is tapped?


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## Chris Kennedy (Nov 19, 2007)

Adam12 said:


> I have never personally worked on a high leg service and was wondering...
> Is the stinger leg always 208v to ground or does it depend on how the XFMR is tapped?


That is the industry standard and what POCO is aiming for, but 199 to 215 is not unusual here.


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## william1978 (Sep 21, 2008)

Adam12 said:


> I have never personally worked on a high leg service and was wondering...
> Is the stinger leg always 208v to ground or does it depend on how the XFMR is tapped?


 I have worked on one that the high leg was 191V to ground.


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## brian john (Mar 11, 2007)

Chris Kennedy said:


> , but 199 to 215 is not unusual here.


Pretty much what I have seen.


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## micromind (Aug 11, 2007)

208 is the theoretical voltage, but it'll vary a bit depending of the phase angles of the primary voltage supply. 

If all 3 phase angles are exactly 120 degrees, the voltage will be exactly 208. If one or more of them is off a bit (very common), then the voltage will be higher or lower. 

The high leg voltage will vary much more on an open delta than with a closed one. 

Rob


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## 220/221 (Sep 25, 2007)

Seems to be in the high 190's around here. I've never seen an actual 208 reading.

I always write "Caution. three phase DELTA syatem. "B" phase is 200V to ground" on the deadfront.

We have these systems in a lot of older (50's-6o's) residential neighborhoods. I guess that original AC units were *all *3 phase so they ran 3 phase delta *just* to power the AC's. 

Since the efficiency of single phase AC units have surpassed the 3 phase units, these services generally get changed out to single phase when their time comes.


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## micromind (Aug 11, 2007)

220; Do they use delta breakers for the A/C units? I've seen quite a few of those, but sometimes there are two panels, one 3 phase, and a larger one thats single phase. 

Rob


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## Adam12 (May 28, 2008)

Awesome guys, thank you. 

My foreman claims 240v. is the voltage of the high leg to ground/nuetral. I only know what Ive read and remember learning in school and have always thought it was 208v.


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## amptech (Sep 21, 2007)

The high leg on a delta will be equal to the voltage of either of the other legs x 1.73.


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## Adam12 (May 28, 2008)

So, phases A to B, A to C, B to C = 240 volts, phases A and C = 120 volts to ground, phase B = 208 volts to ground, is this correct?


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## micromind (Aug 11, 2007)

That's exactly correct.

Rob


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## Adam12 (May 28, 2008)

Thanks.


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## 220/221 (Sep 25, 2007)

> Do they use delta breakers for the A/C units?


Most of the time, yes.


A few years ago, an A/C apprentice for one of our clienyts was told to remove the wires from an A/C that was being replaced. No one knew or mentioned that it was a delta breaker :jester:

The high leg came in contact with someting and fire ensued. The fuse link on the pole finally kicked out but not before setting part of the house on fire. The service/panel was damaged beyond repair and I had to go out and throw up another one.


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