rezzonator
New member
- Location
- Georgia
what is the code article concerning the connection of a three pole breaker on a single phase circuit?...ie; a three pole breaker with one wire connected to it
circuit breakers
- Thread starter rezzonator
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bphgravity
Senior Member
- Location
- Florida
Re: circuit breakers
First of all, why would anyone want to do this? It makes absolutely no sense to make an installation of this type. It is one thing to utilize three single pole breakers tied together to protect a three phase load, but using a manufactured three pole breaker for a single phase single line load is really a bad idea. Fortunetly, 408.16(E) prohibits this!
First of all, why would anyone want to do this? It makes absolutely no sense to make an installation of this type. It is one thing to utilize three single pole breakers tied together to protect a three phase load, but using a manufactured three pole breaker for a single phase single line load is really a bad idea. Fortunetly, 408.16(E) prohibits this!
curt swartz
Senior Member
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
Re: circuit breakers
If you asking about installing a 3-pole breaker in a single phase panel that would be a violation. If you have a 3-pole breaker in a 3-phase panel and just want to use 1-pole with nothing connected to the other 2 that would be ok.
If you asking about installing a 3-pole breaker in a single phase panel that would be a violation. If you have a 3-pole breaker in a 3-phase panel and just want to use 1-pole with nothing connected to the other 2 that would be ok.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: circuit breakers
I don?t think so, but I can?t come up with a stronger argument than 110.3(B): "Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling."
I don?t believe that a 3-pole breaker will provide the proper degree of overcurrent protection, if current is flowing in only one of the poles. Are there any breaker manufacturer?s representatives that might want to offer an opinion?
I don?t think so, but I can?t come up with a stronger argument than 110.3(B): "Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling."
I don?t believe that a 3-pole breaker will provide the proper degree of overcurrent protection, if current is flowing in only one of the poles. Are there any breaker manufacturer?s representatives that might want to offer an opinion?
Re: circuit breakers
Using a 3-pole breaker for a 1p line to neutral application either in a 1ph3w or 3ph4w makes no difference either wise they protection would change in a 3p breaker that happens to supplying a 3ph load that is only drawing a single L-N load.
The heat generated from the adjacent poles of 3p breaker may derate it a bit but not significantly which you wouldn't have if the other two poles were not being used.
But, then again, the same thing occurs is a single phase panel when you have unused, unloaded or lightly loaded breakers next to more heavily loaded breakers. Then, is there really a difference?
However, installing a 3p breaker may be a bit confusing when installed in a single phase panel.
Using a 3-pole breaker for a 1p line to neutral application either in a 1ph3w or 3ph4w makes no difference either wise they protection would change in a 3p breaker that happens to supplying a 3ph load that is only drawing a single L-N load.
The heat generated from the adjacent poles of 3p breaker may derate it a bit but not significantly which you wouldn't have if the other two poles were not being used.
But, then again, the same thing occurs is a single phase panel when you have unused, unloaded or lightly loaded breakers next to more heavily loaded breakers. Then, is there really a difference?
However, installing a 3p breaker may be a bit confusing when installed in a single phase panel.
bphgravity
Senior Member
- Location
- Florida
Re: circuit breakers
Am I not understanding 408.16(E) properly? It states a 3-phase disconnect or overcurrent protection devices shall NOT be connected to the bus of any panelboard that has less than 3-phase buses. Does this not mean no 3-phase breakers in single phase panels?
Am I not understanding 408.16(E) properly? It states a 3-phase disconnect or overcurrent protection devices shall NOT be connected to the bus of any panelboard that has less than 3-phase buses. Does this not mean no 3-phase breakers in single phase panels?
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: circuit breakers
Yes, but that's not what is being discussed. The concept here is 3-phase breaker in a 3-phase panel with only 1 wire attached (i.e., to one of the three poles). I don't think 408.16(E) would apply here.
I am, however, reconsidering my previous posing, in view of a 3-phase multi-wire circuit for which only one circuit may be carrying current at a given point in time. Again I ask, can we get an opinion from a breaker manufacturer?
Yes, but that's not what is being discussed. The concept here is 3-phase breaker in a 3-phase panel with only 1 wire attached (i.e., to one of the three poles). I don't think 408.16(E) would apply here.
I am, however, reconsidering my previous posing, in view of a 3-phase multi-wire circuit for which only one circuit may be carrying current at a given point in time. Again I ask, can we get an opinion from a breaker manufacturer?
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