I have seen this situation on occasions and am wondering if it is a legal installation. Using a single pole breaker on the High leg of a delta service and the neutral, the electrician has fed a 220 volt electric heater and going down the line of the buss bar has fed other equipment that would normally need a 2 pole breaker using only 1 pole and the neutral. What are the potential problems if any with this type of installation.
Delta service feeding 220 Loads off of 1 phase
- Thread starter BigSal57
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Re: Delta service feeding 220 Loads off of 1 phase
Well, since it is one ungrounded conductor & one grounded conductor that is serving the 208V. load, I do not know of a place in the NEC where a 2-pole bkr. would be required.
But even if NEC does not prohibit, I do not like it. The highleg delta system has its purposes. I do not feel that this is one of them.
It is "cheezy". I like to see things done in a common KISS manner.
Well, since it is one ungrounded conductor & one grounded conductor that is serving the 208V. load, I do not know of a place in the NEC where a 2-pole bkr. would be required.
But even if NEC does not prohibit, I do not like it. The highleg delta system has its purposes. I do not feel that this is one of them.
It is "cheezy". I like to see things done in a common KISS manner.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
Re: Delta service feeding 220 Loads off of 1 phase
The breaker must be rated for the voltage, too.
The breaker must be rated for the voltage, too.
charlie
Senior Member
- Location
- Indianapolis
Re: Delta service feeding 220 Loads off of 1 phase
The single pole circuit breaker must be rated for the full voltage and the equipment will get something in the neighborhood of 208 volts, not 240 volts.
The single pole circuit breaker must be rated for the full voltage and the equipment will get something in the neighborhood of 208 volts, not 240 volts.
- Location
- New Jersey
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- Journeyman Electrician
Re: Delta service feeding 220 Loads off of 1 phase
I'd say that it's a violation since they don't make a single pole 208 volt CB.
I'd say that it's a violation since they don't make a single pole 208 volt CB.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Delta service feeding 220 Loads off of 1 phase
There are plenty of breakers designed for 240 or 480/277, and often used for single-phase 277v lighting circuits, so the voltage issue is not a big deal.
I looked through the '02 NEC and couldn't find anything mentioned about this application. It doesn't appear to be specifically prohibited.
A couple of sites I looked through mentioned: "Last, the "high leg" is never used as a single-phase source because no ground or grounded neutral exists for this circuit."
Then I found this in the archives via the search:
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=18;t=002214
[ May 28, 2005, 11:24 PM: Message edited by: LarryFine ]
There are plenty of breakers designed for 240 or 480/277, and often used for single-phase 277v lighting circuits, so the voltage issue is not a big deal.
I looked through the '02 NEC and couldn't find anything mentioned about this application. It doesn't appear to be specifically prohibited.
A couple of sites I looked through mentioned: "Last, the "high leg" is never used as a single-phase source because no ground or grounded neutral exists for this circuit."
Then I found this in the archives via the search:
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=18;t=002214
[ May 28, 2005, 11:24 PM: Message edited by: LarryFine ]
physis
Senior Member
Re: Delta service feeding 220 Loads off of 1 phase
National Electrical Code used to prohibit connection of single phase load from the high leg to neutral. There are several reasons why:
1. Such a load puts extra load on the center tapped winding of the supply transformer and for that current the center tapped winding runs at ZERO internal power factor. Just simply avoiding generation of heat that does not have to be there.
2. Some utilites did cheat metering using a form 12s meter with the high leg effectively not metering any load connected high leg to neutral. A form 12s meter is what is used for 3-wire network and 3-wire 3-phase. When applied to a 4-wire delta system a form 12s meter meters neither the high leg nor the neutral. All loads in this application have to have connection(s) to the low leg(s) to be metered.
3. In a lot of panels 1 pole circuit breakers are only rated 120 volts. This is a circuit breaker misapplication that also occurs on 240 volts corner grounded.
The only legitimate high leg to neutral loads are voltmeter coils and the potential coils of wattmeters, kilowatthour meters, and so forth.
[ May 29, 2005, 02:32 AM: Message edited by: mc5w ]
National Electrical Code used to prohibit connection of single phase load from the high leg to neutral. There are several reasons why:
1. Such a load puts extra load on the center tapped winding of the supply transformer and for that current the center tapped winding runs at ZERO internal power factor. Just simply avoiding generation of heat that does not have to be there.
2. Some utilites did cheat metering using a form 12s meter with the high leg effectively not metering any load connected high leg to neutral. A form 12s meter is what is used for 3-wire network and 3-wire 3-phase. When applied to a 4-wire delta system a form 12s meter meters neither the high leg nor the neutral. All loads in this application have to have connection(s) to the low leg(s) to be metered.
3. In a lot of panels 1 pole circuit breakers are only rated 120 volts. This is a circuit breaker misapplication that also occurs on 240 volts corner grounded.
The only legitimate high leg to neutral loads are voltmeter coils and the potential coils of wattmeters, kilowatthour meters, and so forth.
[ May 29, 2005, 02:32 AM: Message edited by: mc5w ]
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Delta service feeding 220 Loads off of 1 phase
Can we take this to mean that it's now legal?
charlie
Senior Member
- Location
- Indianapolis
Re: Delta service feeding 220 Loads off of 1 phase
We will not guarantee the 208 voltage to be stable because we have so many open delta services. If that type of connection is tending to collapse the delta and causing voltage problems on the false leg, we will walk away from the situation until all of the single phase 208 is removed. We absolutely do not like this type of installation and will not support it but the Code does not prohibit it as far as I can tell.
We will not guarantee the 208 voltage to be stable because we have so many open delta services. If that type of connection is tending to collapse the delta and causing voltage problems on the false leg, we will walk away from the situation until all of the single phase 208 is removed. We absolutely do not like this type of installation and will not support it but the Code does not prohibit it as far as I can tell.
Re: Delta service feeding 220 Loads off of 1 phase
I had heard of the "collapsing hi-leg open delta",like charlie mentions, before.
Also, of course there are 1-pole bkrs. rated 277V. But if using a plain-jane 240V. maximum panelboard (like Square D NQOD), then the Square D ED type 277V. rated bkrs. aren't gonna fit in the 240V. max panel.
This whole idea of the 1-pole bkr. serving 208V. hi-leg load is a bad deal, whether NEC specifically prohibits or not.
mc5 - What NEC edition was it that prohibited?
I had heard of the "collapsing hi-leg open delta",like charlie mentions, before.
Also, of course there are 1-pole bkrs. rated 277V. But if using a plain-jane 240V. maximum panelboard (like Square D NQOD), then the Square D ED type 277V. rated bkrs. aren't gonna fit in the 240V. max panel.
This whole idea of the 1-pole bkr. serving 208V. hi-leg load is a bad deal, whether NEC specifically prohibits or not.
mc5 - What NEC edition was it that prohibited?
Re: Delta service feeding 220 Loads off of 1 phase
I think this is not a code compliant installation.
1. systems of different voltage to ground:
the grounded conductor shall be identified differently i.e. White for 120vac , and Grey for higher voltage. How can you comply with this when it is the same conductor?
2. The NEC talks about nominal voltage assigned to systems as: 120/240 or 480/277 or 600 there are no systems at 120/208/240
3. The circuit breaker issue , not Identified for it use.
frank
I think this is not a code compliant installation.
1. systems of different voltage to ground:
the grounded conductor shall be identified differently i.e. White for 120vac , and Grey for higher voltage. How can you comply with this when it is the same conductor?
2. The NEC talks about nominal voltage assigned to systems as: 120/240 or 480/277 or 600 there are no systems at 120/208/240
3. The circuit breaker issue , not Identified for it use.
frank
paul
Senior Member
- Location
- Snohomish, WA
Re: Delta service feeding 220 Loads off of 1 phase
Can we assume that this system is installed on a 240V panelboard? I've seen 480 panelboards used on some 120/208V systems before, not that I agree with the cost/benefit of such an installation. If this is the case, the single pole breakers are rated for 277V and would be legal.
Can we assume that this system is installed on a 240V panelboard? I've seen 480 panelboards used on some 120/208V systems before, not that I agree with the cost/benefit of such an installation. If this is the case, the single pole breakers are rated for 277V and would be legal.
Re: Delta service feeding 220 Loads off of 1 phase
paul,
Are you saying it's ok to use a 480/277vac panel on a 120/240vac system? It would have to be identified for that use,I have not seen any.
What about the single grounded conductor,having two different voltages off of it,A,C,N 120v and B,N 208v ,the code clearly states that the grounded conductor of different voltage systems must be identified by -------Grey/White---,how do you comply with this,when it is the same conductor?
I guess the point is that this has been addressed a few times on this forum and gets brushed aside as "Well i guess it's ok" ! Then someone reading it says WOW ,I didn't know you could do that,that's cool. I still think it's a violation of the above stated reasons.
frank
paul,
Are you saying it's ok to use a 480/277vac panel on a 120/240vac system? It would have to be identified for that use,I have not seen any.
What about the single grounded conductor,having two different voltages off of it,A,C,N 120v and B,N 208v ,the code clearly states that the grounded conductor of different voltage systems must be identified by -------Grey/White---,how do you comply with this,when it is the same conductor?
I guess the point is that this has been addressed a few times on this forum and gets brushed aside as "Well i guess it's ok" ! Then someone reading it says WOW ,I didn't know you could do that,that's cool. I still think it's a violation of the above stated reasons.
frank
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