SINGLE PHASE ON A THREE PHASE BREAKER

Status
Not open for further replies.
J

jasonbrozen

Member
I NEED ADVICE ON A BREAKER QUESTION. I AM ARGUING WITH THE OWNER OF THE COMPANY THAT IT IS WRONG TO INSTALL 2 WIRES ON A THREE PHASE BREAKER. I DONT THINK THERE IS ANY CODE TO THIS WITH THE EXCEPTION OF 110-3(B). I THINK THIS INSTALL IS CHEESY AND DOES NOT REPRESENT THE ELECTRICICAN WELL. ANY COMMENTS WOULD BE MUCH APPRECIATED. :confused:
 
K

kiloamp7

Senior Member
Re: SINGLE PHASE ON A THREE PHASE BREAKER

If you mean - wiring only (2) poles of a (3) pole bkr. I agree . Do not do it. It is "cheesy", & unprofessional. IMO, it could be used temporarily in an emergency. But that's it.

It is especially bad if the 3-pole bkr. is installed in a 1-phase panel, which I have seen.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: SINGLE PHASE ON A THREE PHASE BREAKER

No problem.

Why not use the "spare", after all, that's why the owner bought it in the first place. But, don't waste money buying a 3pole just in case.
 
J

john m. caloggero

Senior Member
Re: SINGLE PHASE ON A THREE PHASE BREAKER

Gentlemen: The correct answer to the question is 110.3(B) and can be backed up with the following from the UL Molded-Case circuit breakers 600 volts or less Marking Guide: "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-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.
 
B

bfd

Member
Re: SINGLE PHASE ON A THREE PHASE BREAKER

I would use it also, just rewrite the panel directory for that breaker space.
 
J

jasonbrozen

Member
Re: SINGLE PHASE ON A THREE PHASE BREAKER

I AM MOSTLY INTERESTED IN WHAT THE UL LISTING IS FOR THIS SPECIFIC BREAKER. THIS BREAKER IS A ITE/SIEMENS BQ3B020. I CANT SEEM TO FIND THE LISTING ON THE UL SITE. DOES ANYONE KNOW HOW TO FIND SUCH A LISTING? TECHNICALLY I KNOW THAT THERE WOULD BE NO PROBLEMS WITH HOOKING THIS UP. THE COMMON TRIP WOULD STILL WORK AND SO ON. AT THIS POINT IM BEING STUBBORN AND WANT TO WIN AN ARGUMENT. THANKS FOR THE HELP. :confused:
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: SINGLE PHASE ON A THREE PHASE BREAKER

Hi Jason welcome to Mike's forum.

Can you do us all a favor and stop using all capitols. Around here that is yelling.

Jason the question has been answered.

A BQ3B020 is a 3 pole 20 amp breaker and as long as you install it in a the correct 3 phase panel you are able to use one, two or three poles of it.

The NEC nor UL address "Cheesiness" :)
 
J

jasonbrozen

Member
Re: SINGLE PHASE ON A THREE PHASE BREAKER

Sorry,

I am new at forum communication. I appreciate the input and are fully aware that the breaker will work (as I stated earlier) just fine. It is a fact as well that 110-3(B) would exclude this breaker from use if the manufacturer does not instruct installation of this type or does not list the breaker for this use. My other earlier question is how to find UL information on a specific breaker. I have read some previous post and have come up with no answers. I am not a new electrician and have a long standing relationship with the owner. So when I said It was a argument, that might have been a strong statement. Again I appreciate all responses. It seems that this issue of cheesiness is strongly debated in previous forums (as far as the breaker use issue). The code book does not address cheesiness but I think it might be in a NFPA note somewhere. Thanks again. :)
 
T

templdl

Senior Member
Location
Wisconsin
Re: SINGLE PHASE ON A THREE PHASE BREAKER

As a former sales and applications engineer for one of the largest breaker manufactures using a 3p breaker for 2p applications was never an issue and was common if a 3p was handy and available.
You could even use only 1p if you wanted to but is rare as I can't recall any questions on it.
The only think that does change is the temperature rise of the breaker which will be higher when more poles are used at a given ampacity. The TM trip curve would be shifted a bit to the right which means that it would take a tad more overcurrent to trip the breaker which would apply to physically TM breakers with bi-metallic overload elements. Knowing that breakers are commonly calibrated +-10% anyway the difference between applying 3p vs 2p would be like splitting hairs and insignificant anyway.
Sometimes one gets to knit picking when there are so many variables anyway, like the ambient temperature outside the enclosure as it affects the interior, the ambient temp inside the enclosed which is largely dependent upon the loads of other breakers and cable, etc., all of which affect the big-metallic thermal element a the breaker without even considering its load.
I've disassemble breakers up to 2500a frames to see how the work and are calibrated as well as
adding accessories. It is also interesting if you are able to do a side by side comparison of breakers with different kaic rating comparing how the manufacturer changes the arc chute configuration and increase the speed at which the contacts open to clear the arc in order to obtain higher KAIC ratings.
I you have an old breaker take if apart and identify the thermal and magnetic elements, and how they mechanically trip the breaker. Then take a look at the arc chutes and moving and stationary contacts.
Taking apart these products often takes the mystery about what's inside that black box.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: SINGLE PHASE ON A THREE PHASE BREAKER

It is a fact as well that 110-3(B) would exclude this breaker from use if the manufacturer does not instruct installation of this type or does not list the breaker for this use.
Click to expand...
This is not true.

The UL Marking Guide quoted by John. says the only time markings would be required is if the 3 pole breaker was being used on a single phase service. No specific instructions are required for using 2 poles of a three pole breaker which is installed in a 3 phase system.
 
Status
Not open for further replies.
Top