2 Pole load on 3 pole device

[cleveland]

We have a single phase load that will be fed from an old circuit breaker panel. Is there any problem code wise in connecting a single phase load to a 3 pole breaker in a panel? We would clearly indicate that the breaker feeds "single phase load ..."

Some folks are saying "well the device (3 pole breaker) isn't being used as designed" I'm of the mind that it is a multipole overcurrent device that is only sensing current on two of the possible three poles.

Thanks for your time.

 

[barbeer]

I am not aware of any problem in doing that. Almost the same as feeding a 120volt circuit from a 2 pole breaker, each phase should sense current individually.?

 

[Buck Parrish]

In 08 it is required, to have individual 120 volt circuits together. The breaker must be tied tgether if you are sharing a neutral. This is a major code change that also effects residential .

If you are not sharing a neutral it is not allowed. (??)

Also make sure ytou don't have a high leg.

 

[dnem]

Some folks are saying "well the device (3 pole breaker) isn't being used as designed"

Yeah that's the question, the rating.

What do you think about this quote:
UL Molded Case Circuit Breakers Marking Guide '07
page 17
33. 3-Pole - 1-Phase Rated - 3-pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, "For 1-phase connections, use two outside poles," or an equivalent statement. A 3-phase breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked.

It's not very clear to read, but if you read it over and over again until it clicks, I think it's telling you that what you're doing is OK.

I think it's saying that a 3-pole in a 3-phase supplied panel can be used on a single phase [2 hot] circuit. . And a 3-pole in a single-phase supplied panel can be used on a single phase [2 hot] circuit only if the breaker is marked with something like, "For 1-phase connections, use two outside poles".

Is that how you understand it ?

David

 

[jim dungar]

Yeah that's the question, the rating.

What do you think about this quote:
UL Molded Case Circuit Breakers Marking Guide '07
page 17
33. 3-Pole - 1-Phase Rated - 3-pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, "For 1-phase connections, use two outside poles," or an equivalent statement. A 3-phase breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked.

It's not very clear to read, but if you read it over and over again until it clicks, I think it's telling you that what you're doing is OK.

I think it's saying that a 3-pole in a 3-phase supplied panel can be used on a single phase [2 hot] circuit. . And a 3-pole in a single-phase supplied panel can be used on a single phase [2 hot] circuit only if the breaker is marked with something like, "For 1-phase connections, use two outside poles".

Is that how you understand it ?

David

David,

All UL 489 breakers have been tested to on all pole combinations 1, 2, and 3 pole. The markings are there IF there are specific prohibitions not permissions. You can always use fewer poles than the maximum number on the breaker, however you can not install the breaker into a panel that has fewer bus bars unless the breaker is so marked. This prohibition is similar to that of NEC2005 408.36(E) against delta breakers.

 

[dnem]

I don't think our statements are in conflict and after reading the UL paragraph yet once again, I think we're both of our statements are correct.

I think it's saying that a 3-pole in a 3-phase supplied panel can be used on a single phase [2 hot] circuit. . And a 3-pole in a single-phase supplied panel can be used on a single phase [2 hot] circuit only if the breaker is marked with something like, "For 1-phase connections, use two outside poles".

All UL 489 breakers have been tested to on all pole combinations 1, 2, and 3 pole. The markings are there IF there are specific prohibitions not permissions. You can always use fewer poles than the maximum number on the breaker, however you can not install the breaker into a panel that has fewer bus bars unless the breaker is so marked. This prohibition is similar to that of NEC2005 408.36(E) against delta breakers.

 

[jim dungar]

Yes, I believe we are saying the same thing.

Any combination of breaker poles is allowed in a three phase panel.
A three phase breaker can only be used in a single phase panel if it is so marked.

 

[iwire]

I will say I am confused.

a 3-pole in a single-phase supplied panel can be used on a single phase [2 hot] circuit only if the breaker is marked with something like, "For 1-phase connections, use two outside poles".

IF I install a 3 pole breaker in a single phase panel and only use the outer poles I will be using the same phase for each conductor.

I have no idea why I would want to do that.

 

[jim dungar]

I will say I am confused.



IF I install a 3 pole breaker in a single phase panel and only use the outer poles I will be using the same phase for each conductor.

I have no idea why I would want to do that.

You are reading slightly out of context. The original statement was an example of how a 3-pole breaker might be labeled.

 

[iwire]

You are reading slightly out of context. The original statement was an example of how a 3-pole breaker might be labeled.

I see now, thanks. :smile:

 

[dnem]

I will say I am confused.



IF I install a 3 pole breaker in a single phase panel and only use the outer poles I will be using the same phase for each conductor.

I have no idea why I would want to do that.

You are reading slightly out of context. The original statement was an example of how a 3-pole breaker might be labeled.

I see now, thanks. :smile:

I'm glad you understand. . I wish I did also. . But I don't. . Altho I didn't specifically state it, that was part of my original problem with that whitebook paragraph. . I couldn't make sense of all of it and still can't.

The 2 differences between the 2 sentences seem to be obvious enough.

UL Molded Case Circuit Breakers Marking Guide '07
page 17
33. 3-Pole - 1-Phase Rated - 3-pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, "For 1-phase connections, use two outside poles," or an equivalent statement. A 3-phase breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked.

Sentence 1 - single phase system/panel
It starts out talking about 3 phase,
"3-pole circuit breakers are suitable for use on 3-phase systems only, ....."
and then switches to give direction for single phase,
"..... unless marked to indicate use on 1-phase systems, such as, "For 1-phase connections, use two outside poles," or an equivalent statement."
single phase - "marked to indicate use"

Sentence 2 - 3 phase system/panel
This sentence flips back to 3 phase,
"A 3-phase breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked."
3 phase - "without ..... being specifically marked"

Going back to the single phase system/panel, can anybody give me even one single example of when you could terminate on a 3pole breaker "For 1-phase connections, use two outside poles" and get anything other than 2 of the same hots ? . Is there any situation/configuration where you could land 2 wires on the outside poles of a 3pole breaker in a single phase panel and energize the load ?

The original statement was an example of how a 3-pole breaker might be labeled.

Can you give me one example of when the 3 pole breaker might be labeled, "For 1-phase connections, use two outside poles", an example that stays within the context of the sentence that is giving direction about use in a single phase system/panel ?

David

 

[dlhoule]

David, I believe they are referring to the load, not the panel. If you are not in a 3 phase panel you would not want to use a 3 pole breaker; and if you did, you would not be using the two outside poles.:smile:

 

[jim dungar]

Can you give me one example of when the 3 pole breaker might be labeled, "For 1-phase connections, use two outside poles", an example that stays within the context of the sentence that is giving direction about use in a single phase system/panel ?

David

Not all circuit breakers are mounted to bus bars in a panelboard, some are lugs in and lugs out which could easily have the single phase connections to the outside two poles. Or, say you have a minbreaker installed in a three phase panel but you want to feed it with only single phase, again it would be possible to use just the two outside poles. The only time it doesn't work would be with a 3-pole breaker installed in a two bus panel.