paralleling a 2 pole breaker

Status
Not open for further replies.
First of all it won't work the way the OP has described it. A 2-pole breaker can't be on the same phase twice.

Pierre C Belarge said:
I am curious, what makes people think about this type of installation?
Click to expand...

I've seen it done a few times when you need a temporary hookup for some 208 volt equipment. Iron worker wants a welder hookup for one weld and you have no 40 amp CB in the panel so you wire two 20 amps in parallel. Even though is had been done it that doesn't make it right.:rolleyes:
 
Twoskinsoneman said:
Is there a code against paralleling a 2pole breaker? Basically using a 2 pole 20amp breaker for a 40amp Line-to-neutral circuit.
Click to expand...
I am confused by the question. What voltage would the equipment be needing? If you are talking about a 120 volt, 40 amp load, then two separate 20 amp breakers, both connected to the same phase, would give it to you. And that would indeed be a parallel connection. But it would be illegal, per the article Bob cited, and it would be particularly dangerous.

If the load needs 40 amps at 240 (or 208) volts, then as Rob pointed out, a 2-pole breaker will not give it to you. To that I will add that this configuration would not constitute a parallel connection.

May I ask for the reason for the question, and for the nature of the equipment involved? Just curious.
 
charlie b said:
I am confused by the question. What voltage would the equipment be needing? If you are talking about a 120 volt, 40 amp load, then two separate 20 amp breakers, both connected to the same phase, would give it to you. And that would indeed be a parallel connection. But it would be illegal, per the article Bob cited, and it would be particularly dangerous.

If the load needs 40 amps at 240 (or 208) volts, then as Rob pointed out, a 2-pole breaker will not give it to you. To that I will add that this configuration would not constitute a parallel connection.

May I ask for the reason for the question, and for the nature of the equipment involved? Just curious.
Click to expand...

I do come up with some weird questions I know. Thanks for you patients considering I'm in a specialized field. Anyway 95% of the panels we use are custom made panels designed by me. A hinged door has the circuit breakers mounted on it.

The breakers are stud terminated and yes I was talking about a 120v circuit. It is stupid and the only possible reason I can think to do it is if you happen to not have an 80a breaker but you have a 2-pole 40 handy.
I agree it not allowed (that's for the code iwire). Why is it dangerous though?

Here's an example of a panel

panel1.jpg
 
I doubt the NEC applies to your equipment.

As far as why it could be dangerous is that unless you mechanically tie the two breakers together even if one is opened the circuit remains hot which could be nasty surprise for the person servicing the unit.

All that said, I see fuses paralleled fairly often in HVAC and other factory produced equipment.
 
Last edited:
Twoskinsoneman said:
Why is it dangerous though?
Click to expand...
If the contacts do not operate at the same time, one set of contacts will end up carrying the entire amount of current. This may not be a big deal for an occasional condition but, the effects of switching (making and breaking) excessive currents is one reason there are switching rated breakers and HP rated switches.
 
iwire said:
I doubt the NEC applies to your equipment.

As far as why it could be dangerous is that unless you mechanically tie the two breakers together even if one is opened the circuit remains hot which could be nasty surprise for the person servicing the unit.

All that said, I see fuses paralleled fairly often in HVAC and other factory produced equipment.
Click to expand...

I did say a two pole breaker. Meaning two poles mechanically tied together.

Who decides that the NEC applies to them? We as a company choose to impliment the standards of the NEC just like any state etc...

I we choose to impliment the NEC why wouldn't Article 240 apply to the breakers we use?
 
jim dungar said:
If the contacts do not operate at the same time, one set of contacts will end up carrying the entire amount of current. This may not be a big deal for an occasional condition but, the effects of switching (making and breaking) excessive currents is one reason there are switching rated breakers and HP rated switches.
Click to expand...

Why would only one contact open? Has this ever happen to a 2pole breaker for you?
 
Twoskinsoneman said:
. . . the only possible reason I can think to do it is if you happen to not have an 80a breaker but you have a 2-pole 40 handy.
Click to expand...
I still do not understand what you are trying to describe. Fundamental to the issue is that if you have 40 amps flowing in one pole of a 2-pole breaker, and if you have 40 amps flowing through the other pole of the same 2-pole breaker, then the ?total amps? is 40, not 80. But this is related to a 2-pole breaker that you install in a 120/240 volt panel, to serve a single 40 amp load. You are talking about a breaker you plan to install inside a panel of your own design.

So let me ask this. Are you saying that you take a 2-pole, 40 amp breaker out of the box, mount it inside your panel, take a conductor (that is rated for 80 amps) from your internal power supply, connect it to one terminal on the line side of the 2-pole breaker, connect a jumper (that is rated for 80 amps) from that line-side terminal to the adjacent line-side terminal, connect a similar jumper on the load side, and finally run another conductor (that is rated for 80 amps) from the load side of this 2-pole breaker to the downstream load? Have I correctly described your basic design intent?

If that is what you are talking about, then let me pose a question for the membership. Looking at the first sentence of 240.8, can it be said that twoskinsoneman is the ?factory,? and that this usage is indeed ?factory installed,? so that the proposed installation is therefore allowable? Or can we simply say that this is a manufactured product to which the NEC does not apply, and call it a day?
 
I don't think the NEC applies to your work.

90.2 (B) Not Covered. This Code does not cover the following:
(1) Installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles
FPN: Although the scope of this Code indicates that the Code does not cover installations in ships, portions of this Code are incorporated by reference into Title 46, Code of Federal Regulations, Parts 110?113.
 
iwire said:
That is my opinion.
Click to expand...

Let's pretend like is doesn't matter because is DOESN'T.
If I sign a contract stating I will follow the standards set in the NEC then that's what I will do to avoid liability issues.

"Calling it a day" seems to imply that my inquiry is iwire worthy because I don't happen to be in the same cliche as you are.

My post dealt with a specific problem with circuit breakers. Applicability is really irrelavent. I only described the rest in an attempt to show how the both poles of the breaker were on the same phase.
 
charlie b said:
I still do not understand what you are trying to describe. Fundamental to the issue is that if you have 40 amps flowing in one pole of a 2-pole breaker, and if you have 40 amps flowing through the other pole of the same 2-pole breaker, then the ?total amps? is 40, not 80. But this is related to a 2-pole breaker that you install in a 120/240 volt panel, to serve a single 40 amp load. You are talking about a breaker you plan to install inside a panel of your own design.

So let me ask this. Are you saying that you take a 2-pole, 40 amp breaker out of the box, mount it inside your panel, take a conductor (that is rated for 80 amps) from your internal power supply, connect it to one terminal on the line side of the 2-pole breaker, connect a jumper (that is rated for 80 amps) from that line-side terminal to the adjacent line-side terminal, connect a similar jumper on the load side, and finally run another conductor (that is rated for 80 amps) from the load side of this 2-pole breaker to the downstream load? Have I correctly described your basic design intent?
Click to expand...

This is the exact situation. But I wanted to consider if it was legal within the realm of the NEC, not whether or not it was within the realm. And of course why it would be dangerous.
Thanks
 
Twoskinsoneman said:
Let's pretend like is doesn't matter because is DOESN'T.
If I sign a contract stating I will follow the standards set in the NEC then that's what I will do to avoid liability issues.

"Calling it a day" seems to imply that my inquiry is iwire worthy because I don't happen to be in the same cliche as you are.

My post dealt with a specific problem with circuit breakers. Applicability is really irrelavent. I only described the rest in an attempt to show how the both poles of the breaker were on the same phase.
Click to expand...

Wow, kind of angry over nothing.

Of course your more then free to follow the NEC, I never said otherwise.

But your opening question

Is there a code against paralleling a 2pole breaker? Basically using a 2 pole 20amp breaker for a 40amp Line-to-neutral circuit
Click to expand...

sure made it sound to me like you wanted to know the rules.

If your choosing to follow the NEC then IMO your proposed installation violates 240.8.
 
iwire said:
Wow, kind of angry over nothing.

Of course your more then free to follow the NEC, I never said otherwise.

But your opening question



sure made it sound to me like you wanted to know the rules.

If your choosing to follow the NEC then IMO your proposed installation violates 240.8.
Click to expand...

Thank you 240.8 was exactly what I was looking for.
Don't mean to sound angry. Seems like the few of us outside the normal electrical field are sort of ostracized...

I DID want to know the rules pertinent to my OP. Not my insane choice to follow the NEC when I don't have to. :grin:

I bet I can back through my question and find a dozen times someone looks at my profile then answers my question with "you don't fall under the NEC so it doesn't matter". It just isn't helpful
 
Twoskinsoneman said:
Why would only one contact open? Has this ever happen to a 2pole breaker for you?
Click to expand...
I said "open at the same time". It is very hard to have both contacts perfectly matched, as soon as one starts to draw an arc (which creates resistance) the current will begin to rise in the other contact; so by the time the circuit is broken, one contact may be doing most of the work. I am not saying this the reason against paralleled OCPD's, only that it may be part of a reason.
 
for small breakers like you are talking about it probably is not a major safety problem, especially if the poles are tied together.

it still not to code.

and I agree your equipment does not have to meet code, at least the NEC.
 
petersonra said:
for small breakers like you are talking about it probably is not a major safety problem, especially if the poles are tied together.

it still not to code.

and I agree your equipment does not have to meet code, at least the NEC.
Click to expand...

:grin: Anyone else llike to tell me I don't fall under the NEC or shall we "call it a day"!?

Thanks everyone for the actually helpful opinions.
 
Status
Not open for further replies.
Top