Question of the day

[LarryFine]

Is a 3-pole circuit breaker mounted in a single-phase panel a "3-phase overcurrent device"?

I would say it's a "3-pole overcurrent device," rgeardless of where it's installed.

 

[hurk27]

WoW, I never thought putting a 3-phase breaker in a single phase panel was, against the NEC, but if read like it is, in the 2002 408.16(E) seem to state this.:-?

We used a three pole breaker to protect those office stations, that come with 3-wire MWBC with a over sized neutral, and we feed them with an over sized neutral from the panel. this way if work was done then all the circuits the J-box, and conector plugs that plud in to provide power would be shut off.

 

[david luchini]

I can. A Delta breaker is a 3-pole breaker that only receives power from two panel buses. The third pole get's its power from an external input, not unlike a GFCI's neutral terminal, which has no panel main terminal.

I have pointed out in the past that a high-leg Delta service is, with the exception of the high leg, identical to a 120/240v 1ph service, and that early high-leg services were actually modifications to 1ph services.

The Delta breaker allowed a 1ph panel to supply a 3ph load by having the high leg brought into the panel for the sole purpose of feeding the Delta breaker's third conductor, and the breaker to operate properly.

Larry, you're so contrary. :grin: But seriously, the code section in question prohibits 3-phase disconnects and overcurrent devices in one sentence, and delta breakers in the next sentence. I completely agree with you though, that as the code is written, it would prohibit a 3pole c/b in a 120/240v panel but allow it to be installed in a high-leg delta panel since it has 3 phase buses, which would be an unusual condition.

I would say it's a "3-pole overcurrent device," rgeardless of where it's installed.

I would agree with this also. I don't think the NEC writers would appreciate us getting caught up in the semantics of what is a "pole"versus what is a "phase" as it applies to this code section.

 

[wasasparky]

I would say it's a "3-pole overcurrent device," rgeardless of where it's installed.

Thanks for making my point.
3-phase OCPD's are not allowed, 3-pole OCPD's are.

Circuit breakers are 1-pole, 2-pole, 3-pole NOT 1-phase, 2-phase, 3-phase

A 3-pole OCPD is a 3-phase OCPD when protecting a 3-phase feeder/branch...

 

[wasasparky]

WoW, I never thought putting a 3-phase breaker in a single phase panel was, against the NEC...

It's not, unless you bring in the high leg to make the 3-pole OCPD a 3-phase OCPD.

We used a three pole breaker to protect those office stations, that come with 3-wire MWBC with a over sized neutral, and we feed them with an over sized neutral from the panel. this way if work was done then all the circuits the J-box, and conector plugs that plud in to provide power would be shut off.

Bingo

 

[wasasparky]

I don't think the NEC writers would appreciate us getting caught up in the semantics of what is a "pole"versus what is a "phase" as it applies to this code section.

It's not semantics, and I'm pretty sure they will still sleep OK at night.:smile:

I forgot to check my panel label to see if it mentions the number of poles allowed...:roll:

I was thinking of asking if a 120/240V system is 1-phase or 2-phase, but that can of worms has been opened many times before.
(Another topic where people confuse phase with pole...)