3-pole beaker feeds single phase panel

[anbm]

We are doing the updraging several panels in existing building. We have found out that in some existing panels, they used 3-pole breaker to feed single phase panels by using only 2 phases of breaker and leave the 3rd phase alone.

What section of code address this violation? Thanks!

 

[benaround]

anbm, This has come up a few times recently, IMO, it is not a violation.

 

[anbm]

What's about article 100 definition for listed rule?
Does 3-pole breaker list to be protect 2-pole load?

 

[benaround]

What's about article 100 definition for listed rule?
Does 3-pole breaker list to be protect 2-pole load?

As far as I know, yes it does.

Also, See in the NEC code forum, "using 1 phase of a 3 phase cb. " by Sidd Martin. it is two or three pages in.

 

[jim dungar]

What's about article 100 definition for listed rule?
Does 3-pole breaker list to be protect 2-pole load?

Absolutely. It even protects 1-pole loads.

 

[anbm]

I know it can be used to protect single phase, 1-pole or single phase 2-pole load as long as the load won't trip CB. What I need is some statements from code or manufacturer says that the CB are listed or can be used in this application so I can prove it to the owner. Thanks!

 

[kwired]

I know it can be used to protect single phase, 1-pole or single phase 2-pole load as long as the load won't trip CB. What I need is some statements from code or manufacturer says that the CB are listed or can be used in this application so I can prove it to the owner. Thanks!

I pretty sure you will find nothing in code, noty sure about manufacturers, but if you think about it supplying three conductors with voltage but applying load to only one or two you would still have the same thing. How about supplying a three phase panel and only installing one single pole load in that panel. Nothing wrong with that and the feeder (3 pole) breaker does not care that there is only load on one leg as long as it is below the protection rating.

 

[Ranch]

We have been able to satisfy UL508A and CSA 22.2 with three pole breakers on single-phase loads. But I insist, especially in the case of a moulded case breaker that the two lines coming in are terminated on L1 and L3, a jumper is looped back from T3 to L2 and the load is connected to T1 and T2. This will more evenly distribute heating in the breaker, which undoubtedly leads to more predictable and safer operation of the breaker. It should be obvious as you pass the two lines through all three breaker poles is advantageous. Three phase breakers in so many cases are abundant and often less money.

 

[dwagener]

.......wow

 

[220/221]

Someone is confused.^

Or maybe it's me???

I think this would make smoke.

 

[Ranch]

Someone is confused.^

Draw it out. L1,2,3 is your breaker line side, T1,2,3 is the load side. Use the loop. I'll add this is the only method 3 pole digital trip breakers can be used for single phase loads for those that may encounter that rare case.

 

[Ranch]

And for the Europeans it is R, S, T line and U, V, W load for your breaker termination conventions

 

[Pierre C Belarge]

This is from the UL Marking Guide, on Molded Case Circuit Breakers:

"

34.
3-Pole ? 1-Phase Rated ?​

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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-pole 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."

 

[Ranch]

To Pierre - I'm just not a fan of "use two outside poles" when it is so simple to pass balanced current of two through three. Testing, accreditation and labelling can be apporved in these circumstances.

I'll throw you a curve - how do you handle a 3 phase line reactor in a single phase circuit? That is where the outside poles makes sense (sometimes). Do you believe the outside pole verbiage related to breakers is to alleviate wiring confusion? Outside pole usage makes sense for circuit filters, not breakers

 

[LarryFine]

But I insist, especially in the case of a moulded case breaker that the two lines coming in are terminated on L1 and L3, a jumper is looped back from T3 to L2 and the load is connected to T1 and T2.

It should be obvious as you pass the two lines through all three breaker poles is advantageous.

It may also allow the breaker contacts to last longer, like with relay contacts in series, which behave like they're opening faster.

 

[220/221]

a jumper is looped back from T3 to L2

There is a T3 on a single phase load?

Draw it out. L1,2,3 is your breaker line side, T1,2,3 is the load side

A single phase load will only have T1 and N or T1 and T2.

What am I missing?



While I'm at it....

Three phase breakers in so many cases are abundant and often less money.

In what country/planet?

 

[iwire]

To Pierre - I'm just not a fan of "use two outside poles" when it is so simple to pass balanced current of two through three.

You may not be 'a fan of it' but regardless that is what UL requires and your suggestion to loop back around is all but imposable with most panel supplied breakers here in the USA.

 

[iwire]

It may also allow the breaker contacts to last longer, like with relay contacts in series, which behave like they're opening faster.

Can you provide any references for that?

I have seen you mention it before but have never seen any reference, and if the contacts are rated for the load why would we have to take unusual measures to make them last?

 

[LarryFine]

Can you provide any references for that?

Nothing in print that I can find quickly, but a good friend who builds elevator selectors swears by it from experience.

Doing it acts like contacts opening twice as far twice as fast, and reduce pitting. He says it makes them last longer.

 

[don_resqcapt19]

We have been able to satisfy UL508A and CSA 22.2 with three pole breakers on single-phase loads. But I insist, especially in the case of a moulded case breaker that the two lines coming in are terminated on L1 and L3, a jumper is looped back from T3 to L2 and the load is connected to T1 and T2. This will more evenly distribute heating in the breaker, which undoubtedly leads to more predictable and safer operation of the breaker. It should be obvious as you pass the two lines through all three breaker poles is advantageous. Three phase breakers in so many cases are abundant and often less money.

I assume that we are talking about a breaker that is installed in a 3 phase panel being used to supply single phase loads...there is no way to use all 3 poles as you suggest.