Delta High Leg
- Thread starter jimmie
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electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: Delta High Leg
Is this question for real?
Is this question for real?
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Delta High Leg
I think you could do it if you followed 240.85
I think you could do it if you followed 240.85
Re: Delta High Leg
The March 1995 issue of EC&M magazine had a Reader's Quiz edited by a Robert J Lowrie, one of the questions of which asked this very same question.
In theory it is possible but it cannot be accomplished with standard panelboards. If you think about it you would be taking power from the high leg to the neutral of the "lighting tap" which is, with almost all certainty grounded. How would you protect it with a listed panel?
One of the respondents, J.F.F.,goes on to say " Code wise, there is no direct prohibition of such a 208v connection; but it could not be done by any "proper" connection to the panelboard of such systems."
Also, another respondent, E.D., brought up another point. You get 208v from the high leg to the lighting tap neutral. Then you have the lighting tap which also uses the neutral, 240 L-L and 120v each line to that same neutral. He points out that the NEC prohibits the mix of neutrals of different systems.
The March 1995 issue of EC&M magazine had a Reader's Quiz edited by a Robert J Lowrie, one of the questions of which asked this very same question.
In theory it is possible but it cannot be accomplished with standard panelboards. If you think about it you would be taking power from the high leg to the neutral of the "lighting tap" which is, with almost all certainty grounded. How would you protect it with a listed panel?
One of the respondents, J.F.F.,goes on to say " Code wise, there is no direct prohibition of such a 208v connection; but it could not be done by any "proper" connection to the panelboard of such systems."
Also, another respondent, E.D., brought up another point. You get 208v from the high leg to the lighting tap neutral. Then you have the lighting tap which also uses the neutral, 240 L-L and 120v each line to that same neutral. He points out that the NEC prohibits the mix of neutrals of different systems.
charlie
Senior Member
- Location
- Indianapolis
Re: Delta High Leg
This is probably supplied by an electric utility and may be done with an open delta bank. If this is the case, you will be attempting to collapse the delta a little. The serving electric utility will not guarantee the voltage to the high phase so you will be hanging the customer out on his own. Don't forget that you have to use a full voltage device.
The general rule is don't do it but the Code does not prohibit this installation. Ask any electric utility and the answer will be no, you can't do it but they will not be able to produce anything in writing to prohibit the installation.
In general, it is poor practice and a mark of a jackleg.
This is probably supplied by an electric utility and may be done with an open delta bank. If this is the case, you will be attempting to collapse the delta a little. The serving electric utility will not guarantee the voltage to the high phase so you will be hanging the customer out on his own. Don't forget that you have to use a full voltage device.
The general rule is don't do it but the Code does not prohibit this installation. Ask any electric utility and the answer will be no, you can't do it but they will not be able to produce anything in writing to prohibit the installation.
In general, it is poor practice and a mark of a jackleg.
electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: Delta High Leg
Sorry. I was a little quick with my reply. It just seemed stange why someone would ask if there was any equipment rated for 208V. I see what you are asking now.
Sorry. I was a little quick with my reply. It just seemed stange why someone would ask if there was any equipment rated for 208V. I see what you are asking now.
Re: Delta High Leg
I had an SDG&E lineman tell one of my guys it was OK. I had a helluva time convincing him and the construction superintendant otherwise.
The situation was the plumber had installed 208 volt insta-hots instead of 240 volt units like he should have. The plumber wanted an extra to swap out the heaters. My guy saw a quick solution, grab the stinger with a 1-pole CB. I said "no", my guy asked the lineman working on the service, he said "yes". From there it was me against the word of the all-knowing lineman.
Besides being wholly unconventional, nothing more than the fact I had never seen it done before and my gut feeling kept me from capitulating. I could not, however, find anything in the code restricting this. Perhaps this should be added.
It's interesting to read the technical reasons why this is a bad idea. Once again, thanks go to you guys.
I had an SDG&E lineman tell one of my guys it was OK. I had a helluva time convincing him and the construction superintendant otherwise.
The situation was the plumber had installed 208 volt insta-hots instead of 240 volt units like he should have. The plumber wanted an extra to swap out the heaters. My guy saw a quick solution, grab the stinger with a 1-pole CB. I said "no", my guy asked the lineman working on the service, he said "yes". From there it was me against the word of the all-knowing lineman.
Besides being wholly unconventional, nothing more than the fact I had never seen it done before and my gut feeling kept me from capitulating. I could not, however, find anything in the code restricting this. Perhaps this should be added.
It's interesting to read the technical reasons why this is a bad idea. Once again, thanks go to you guys.
charlie
Senior Member
- Location
- Indianapolis
Re: Delta High Leg
Linemen are not electricians and power company employees generally do not understand wiring past the service. I spent about 1 1/2 hours yesterday and another 45 minutes this morning trying to get one of our guys to understand how the meter fitting is grounded where we are metering a feeder instead of service. He was calling the grounded conductor the neutral, the grounding conductor the bonding conductor, and . . . so on. If I can just get him using the proper names for things, I feel like I would be making progress.
Oh . . . by the way . . . UH . . . electricians are not linemen either.
Linemen are not electricians and power company employees generally do not understand wiring past the service. I spent about 1 1/2 hours yesterday and another 45 minutes this morning trying to get one of our guys to understand how the meter fitting is grounded where we are metering a feeder instead of service. He was calling the grounded conductor the neutral, the grounding conductor the bonding conductor, and . . . so on. If I can just get him using the proper names for things, I feel like I would be making progress.
Oh . . . by the way . . . UH . . . electricians are not linemen either.
lady sparks lover
Senior Member
Re: Delta High Leg
I don't think it would be wise to use the 208V leg, but that is JMO! I just would think the balance of your phases would be off, if and only if you use the high leg as a single pole, not in conjuction with phases A or C. Do they sell a 208, single pole device...I'm not sure.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Delta High Leg
I think you would have to use a 2 pole STRAIGHT RATED breaker, and only use half of it. Again, it is crucial that 240.85 be satisfied.
I think you would have to use a 2 pole STRAIGHT RATED breaker, and only use half of it. Again, it is crucial that 240.85 be satisfied.
Re: Delta High Leg
A quick re-read of my post and I can see how it could be interpreted as condescending, which wasn't the intent at all.
My frustration was rooted in the fact that this gentleman's position as a lineman, the construction superintendent's pre-disposition against replacing the 208 volt heaters, and my inability to come up with a definitive reason against this lineman's advice, put me in a very difficult place in terms of making my case vs his.
No disrespect intended to ANY lineman.
And yes, I did call the manufacturer of the heater to make sure they wouldn't work on 240, which they wouldn't. Ultimately the plumber was payed by the GC to replace the heaters.
No doubt.Originally posted by charlie:
Oh . . . by the way . . . UH . . . electricians are not linemen either.
A quick re-read of my post and I can see how it could be interpreted as condescending, which wasn't the intent at all.
My frustration was rooted in the fact that this gentleman's position as a lineman, the construction superintendent's pre-disposition against replacing the 208 volt heaters, and my inability to come up with a definitive reason against this lineman's advice, put me in a very difficult place in terms of making my case vs his.
No disrespect intended to ANY lineman.
And yes, I did call the manufacturer of the heater to make sure they wouldn't work on 240, which they wouldn't. Ultimately the plumber was payed by the GC to replace the heaters.
Re: Delta High Leg
I would love two further explanations if anyone would like to entertain them:
#1 - How is using the stinger to neutral considered using a neutral of a "different" system.
#2. - How would using current from the stinger to neutral "collapse the delta" and what specifically does that mean?
I would love two further explanations if anyone would like to entertain them:
#1 - How is using the stinger to neutral considered using a neutral of a "different" system.
#2. - How would using current from the stinger to neutral "collapse the delta" and what specifically does that mean?
Re: Delta High Leg
277/480 volt rated breakers were used for the 240 volt lighting circuits coming out of this panel that went across the stinger.
Even the 250 volt bolt-on Siemans 2-pole breakers were "slash rated" 120/240. I was told 2p-20 amp "straight rated" breakers weren't available from Siemans.
277/480 volt rated breakers were used for the 240 volt lighting circuits coming out of this panel that went across the stinger.
thunder15j
Member
- Location
- Cali
Re: Delta High Leg
Standard plug-on and also bolt-on circuit breakers that have a 120/240 volt rating are rated for 240,208 and 120 volt circuits that have a maximum voltage of 120 volts to ground. The circuit breaker contacts are rated for 240 or less. However the breaker case is listed for a maximum of 120 volts to ground.
So,any single pole or 2 pole fed circuit in a 3 phase grounded delta (open or closed) 120/240 volt grounded system should not be fed by the high leg, stinger leg, or whatever one might call it, when our fellow electricians are using a breaker that is rated only for 120 volts to ground.The same holds true for anyone who might handle tie three singles together as a 3 phase breaker feed.
If one were to use the high leg for 208 single pole and 240 volt single phase using the high leg as one of the ungrounded conductors, this could safely be accomplished by using the 480/277 volt rated breakers. This assumes that the utility has pulled same size phase conductors and has sized their transformer bank for loads other than 3 phase. I've seen many installs by our local utility (P, G & E) where the power leg is sized smaller than the other two ungrounded conductors (120 volts to ground).
Standard plug-on and also bolt-on circuit breakers that have a 120/240 volt rating are rated for 240,208 and 120 volt circuits that have a maximum voltage of 120 volts to ground. The circuit breaker contacts are rated for 240 or less. However the breaker case is listed for a maximum of 120 volts to ground.
So,any single pole or 2 pole fed circuit in a 3 phase grounded delta (open or closed) 120/240 volt grounded system should not be fed by the high leg, stinger leg, or whatever one might call it, when our fellow electricians are using a breaker that is rated only for 120 volts to ground.The same holds true for anyone who might handle tie three singles together as a 3 phase breaker feed.
If one were to use the high leg for 208 single pole and 240 volt single phase using the high leg as one of the ungrounded conductors, this could safely be accomplished by using the 480/277 volt rated breakers. This assumes that the utility has pulled same size phase conductors and has sized their transformer bank for loads other than 3 phase. I've seen many installs by our local utility (P, G & E) where the power leg is sized smaller than the other two ungrounded conductors (120 volts to ground).
charlie
Senior Member
- Location
- Indianapolis
Re: Delta High Leg
Bob, I didn't take your post as being condescending and I didn't intend to be putting anyone down in response. That is the trouble with just using this media for conversation. The Graemlins do help a bit though (if I would use them)
Bob, I didn't take your post as being condescending and I didn't intend to be putting anyone down in response. That is the trouble with just using this media for conversation. The Graemlins do help a bit though (if I would use them)
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Delta High Leg
Charlie is this collapse why somtimes we read 190 volts on the stinger instead of 208 volts? In Florida when an electrician made the mistake of connecting a 120 volt fuel pump to the "B" phase that was the voltage we had. and I often wondered why.
Charlie is this collapse why somtimes we read 190 volts on the stinger instead of 208 volts? In Florida when an electrician made the mistake of connecting a 120 volt fuel pump to the "B" phase that was the voltage we had. and I often wondered why.
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