240 v range on 3 phase delta

[malty]

Hi, I do mainly residential wiring and need some help. A customer bought a commercial building that has 3 phase. I have to run a circuit for a 240 volt kitchen range. The panel is a three phase delta with a midpoint neutral tap. Between A phase and N is 120v and the same for phase C to N IS 120v. Phase B (wild leg) is 208v to N. Phase to phase on any two of the three is 240v. Using a two pole breaker one leg is 208v and the other leg is 120v but together their 240v. Is there a problem using this for the stove circuit? If there is a problem using the 208v & 120v to get 240v for the stove how could it be done from this panel.
Thanks

 

[augie47]

since most ranges use the neutral, you should supply the range by phase A, C and the neutral (+ eq ground). Avoid Phase B and it will be just like a 120/240 resid. service.

 

[hillbilly1]

Be sure to check "B"phase is the "high or wild leg", There are many delta services that the high leg is improperly on "C" phase in the panel.

 

[hillbilly1]

Just noticed that you have already verified this, but always be aware that it is not always on "B":smile:

 

[malty]

Thanks Gus, There was only room for the 2 pole breaker in the panel. Without having the panel in front of me I imagine to be able to use A & C phase and avoid B phase I would have to shift the 2 pole breaker over a space which I can't do because all spaces are being used.

 

[malty]

Thanks for the replys. To use A & C phases and avoid B with the 2 pole breaker I think with out haveing the panel in front of me I would have to move the breaker over one space to be on A & C, Correct?? The problem is all spaces are being used.

 

[hillbilly1]

I was friends with a competitor that was installing an exhaust fan in a plant that I had done work in before, I told him to watch out for the high leg, but he ignored my advice and put a breaker in the first open space in the closest panel. After smoke started to roll out of the fan when he turned it on, he found out what a high leg was. He had to run a wire to a panel on the far side of the plant to get 120.:roll:

 

[malty]

I went back and looked at the panel. From what I can figure out is that the 2pole breaker can't be used because anyplace it's plugged in will pick up 120v on one phase and 208 on the other. Could I use a 3 pole breaker and use phase A & C to get the required 120v on each leg and not use the B phase (wild 208v leg)on the breaker to achieve the correct voltage for the stove? Thanks for any help.

 

[mcclary's electrical]

Just do some rearranging

 

[malty]

Just do some rearranging

Yes I can do some rearranging of the breakers but anywhere the 2p breaker is plugged in will pick up 240v on one leg and 208 on the other. I can rearrange to fit the 3pole breaker in. I just need to know if doing this is the correct way to get 120v on each leg using the A & C and not use the B wild leg.Is there another way? Thanks

 

[malty]

Yes I can do some rearranging of the breakers but anywhere the 2p breaker is plugged in will pick up 240v on one leg and 208 on the other. I can rearrange to fit the 3pole breaker in. I just need to know if doing this is the correct way to get 120v on each leg using the A & C and not use the B wild leg.Is there another way? Thanks

OOPS I ment to say the 2p breaker will pick up "120v" on one leg and 208 on the other and will the 3pole breaker work to get the required 120v on A & C and is this the correct way to acheve this. THANKS

 

[jim dungar]

OOPS I ment to say the 2p breaker will pick up "120v" on one leg and 208 on the other and will the 3pole breaker work to get the required 120v on A & C and is this the correct way to acheve this. THANKS

A 3-pole breaker will give you the ability to get phase A & C and to ignore phase B ( which is the 208V-N one).

 

[malty]

Thanks Jim

 

[LarryFine]

Malty, keep in mind that any 240v load that does not use the neutral can be placed in any 2-space space. The range must be used in a space that does not contact the high leg.

While using a 3-pole breaker wouldn't be my first choice, it would work. I'd remove the center terminal's screw just to reduce the likelihood of a future error by someone else.

If you have a 3-space space in the panel, maybe you can relocate one or more 2-pole breakers, and/or one or more 1-pole breakers, to open a 2-space space for A and C phases.

 

[Doug S.]

To expound on what Larry just stated, and please correct if I'm wrong... ... ...

If the range does NOT use the neutral you can put the 2-pole breaker any where you want. If the load is phase-phase with no neutral, (240v) the wild leg is NOT a consideration.

HOWEVER do check that the range is NOT using a ground reference of some sort. The range in my last house used the EGC as a return path for the clock. I KNOW this is not proper, and I did quite a bit of verifying that there was NO spot to connect a neutral. I verified the problem by disconnecting the ground and watching the clock go out... Nice huh? :roll:

My 2?
Doug S.

 

[malty]

Malty, keep in mind that any 240v load that does not use the neutral can be placed in any 2-space space. The range must be used in a space that does not contact the high leg.

While using a 3-pole breaker wouldn't be my first choice, it would work. I'd remove the center terminal's screw just to reduce the likelihood of a future error by someone else.

If you have a 3-space space in the panel, maybe you can relocate one or more 2-pole breakers, and/or one or more 1-pole breakers, to open a 2-space space for A and C phases.

Larry, The phases in this panel alternate 120v to 208v for the breakers so even if the panel had no breakers in it, anywhere you put in a 2 pole breaker one leg would have 120v and the other would have 208. The only way out that I can think of is using the 3 pole breaker. There are other 2 pole breakers in the panel but there for the water heater etc that do not use the neutral and will work with the wild phase B.

 

[Article 90.1]

Malty, is this a single phase sub panel? I know that you said it was three phase, but it sounds similar to a single phase panel that is fed from a three phase panel with the two pole breaker with one pole being on the bastard leg. Ask me how I know this. When I was an apprentice, we fed a sub panel in a BMW showroom from the high leg. When we energized the new panel it sounded like popcorn popping. This is when T-8 electronic ballasts were coming on the scene. The popping was every other electronic ballast, and all of the GFI's in the addition.

Like stated above, you'll want your stove breaker on A & C phase, so spaces: 5 & 7, 11 & 13, 17 & 19, 23 & 25, 29 & 31, 35 & 37, 6 & 8, 12 & 14, 18 & 20, 24 & 26, 30 & 32, or 36 & 38. If need be you may have to move other single pole breakers to make this layout work, of course you will have to make sure to not put any single pole breaker on the bastard leg. If you move a two pole breaker so that one pole is fed from the bastard leg, just make sure that it is a straight 240 volt circuit, with no neutral. Sorry if this post is an overstatement of the obvious.

Your volt meter is your best friend on this project!

 

[malty]

I'm pretty sure what I have here is a three phase delta connected system . Phase A is 120v, phase B is marked orange is 208v and phase C is 120v. 240v can be derived by using any two of three phases. I think I'm learning as we go. And I am making use of my voltmeter to be sure.

 

[LarryFine]

Larry, The phases in this panel alternate 120v to 208v for the breakers so even if the panel had no breakers in it, anywhere you put in a 2 pole breaker one leg would have 120v and the other would have 208.

That should be very incorrect. That would require a 1-phase panel being supplied by the B phase and only one of the others.

Going down either side, you should see A, B, C, A, B, C, etc. A breaker at the C-A position should have both legs at 120v to the neutral.

Make sure this panel is a 3-phase panel, that it has three main terminals or a 3-pole main breaker. Also, are there any 3-pole breakers installed?

 

[hillbilly]

Check out this recent post.

http://forums.mikeholt.com/showthread.php?t=115058

steve