voltage on a 120/208 panel

[Ivan Young]

Gentlemen, I have what might appear be a dumb question, but anyway here goes.
If you have a 120/208 panel with a wild leg on phase B and you connect a two pole
breaker to phase A and B, what voltage would you get?
How about a three pole breaker to phase A B C?
Thanks for any help.

 

[hurk27]

A panel fed from a 4-wire high-leg delta will only have 208 from the B phase to the neutral, between any two phases you will have 240 volts and between A and C phase and the neutral you will have 120 volts.

But your question sounds like your meaning a panel fed from a 120/208 source which is a WYE and will not have a high leg, on these voltage between any two phases will be 208 volts, and any phase and neutral will be 120 volts.

 

[ActionDave]

Not a dumb question.

If you have a wild leg then you do not have a 208/120V panel you have a 240V delta panel. Voltage on any phase to any other phase is 240V. A to B 240V, A to C 240V, B to C 240V, BUT.... Voltage from B to ground is 208V. That is why it is a wild leg, or high leg, or stinger, or bastard son of %$!! leg.

 

[electricalist]

the b phase should be marked orange? but not to be confused with B O Y 277/480 orange b phase?

 

[roger]

Here's an illustration that shows the voltages.

Roger

 

[GoldDigger]

the b phase should be marked orange? but not to be confused with B O Y 277/480 orange b phase?

BOY is not a Code specified standard, and at a site with a high leg supply (service or SDS) you would have to use a different color or tag indicator for your 480Y/277.
Hypothetical question:
What if you had two high leg deltas at different voltages? Orange for both but add a tag or marker of some sort to one?

 

[electricalist]

I agree. Thanks for your clarification on what I was trying to say.. I put the question marks so that someone would correct me if I wasnt stating it factually correct.
On another note I thought a 240 delta panel may have 120/208 on it. I dont remember for sure.
Any equipment I work with I read the name plate or the panel info. We have a customer who has a delta 240 service and the panel said 120/208.
Is that realistic I checked voltage and high leg was on c phase from the riser..
I also never understood why highleg is orange by code yet also used as an agreed 277/480 b phase. Seems like a bad idea

 

[Ivan Young]

Thanks for all the replies gentlemen. If you have your wild leg on the B phase, then if I am not mistaken if you install a breaker in slot 3,9,15,4,10,16, etc., will be 208v. If a two pole breaker is installed between slot 1 and 3 then you are saying the voltage will be 240v. What happens if a three pole breaker is installed in slot 1,3, and 5 what will the voltage be?

 

[GoldDigger]

Thanks for all the replies gentlemen. If you have your wild leg on the B phase, then if I am not mistaken if you install a breaker in slot 3,9,15,4,10,16, etc., will be 208v. If a two pole breaker is installed between slot 1 and 3 then you are saying the voltage will be 240v. What happens if a three pole breaker is installed in slot 1,3, and 5 what will the voltage be?

You can only do this for a load which is wired delta, giving you 240V on all three line to line connections. This ability to support three phase loads is one of the advantages of high leg delta.
If you tried to connect a three phase wye load you would get 120, 120, 208 and you would likely burn out the load.

 

[ActionDave]

Thanks for all the replies gentlemen. If you have your wild leg on the B phase, then if I am not mistaken if you install a breaker in slot 3,9,15,4,10,16, etc., will be 208v.

Voltage to ground will be 208.

If a two pole breaker is installed between slot 1 and 3 then you are saying the voltage will be 240v.

Phase to phase, yes. Same again for slots 3 and 5.

If you put your meter across phase A and ground it reads 120V, phase to ground on B 208V. Same again for slots 3 and 5.... B to ground 208V, C to ground is 120V

What happens if a three pole breaker is installed in slot 1,3, and 5 what will the voltage be?

240V phase to phase. Phase to ground same as above.

 

[Ivan Young]

I must say thanks to you guys for clearing up a lot of misinformation. May the good Lord protect each and every one of you daily in the dangerous job that you do.

 

[hurk27]

You can only do this for a load which is wired delta, giving you 240V on all three line to line connections. This ability to support three phase loads is one of the advantages of high leg delta.
If you tried to connect a three phase wye load you would get 120, 120, 208 and you would likely burn out the load.

Many 3-phase heaters are connected in a WYE but don't have the WYE point bonded to the neutral so they would work just fine on a high-leg delta, the elements are rated at 135.5 volts though, we have some at work like this.