# 2 breakers one branch circuit



## smeric28 (Nov 16, 2009)

ok so i was answering some questions in a diy forum and some crazy HO wants to wire a single branch circuit from two different breakers. I was in the process of telling him what a dumb idea this is, and i was going to include a code reference just for emphasis. But it seems i can't find where this is specifically prohibited. so... can anybody give me a code reference on this one?


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## Bob Badger (Apr 19, 2009)

Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG) the code prohibits it in Article 240. I think it is 240.8


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## JohnJ0906 (Jan 22, 2007)

Bob Badger said:


> Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG) the code prohibits it in Article 240. I think it is 240.8


240.8 is correct.


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## BEAMEUP (Sep 19, 2008)

Bob Badger said:


> Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG)


What?? Are you serious?


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## RePhase277 (Feb 5, 2008)

BEAMEUP said:


> What?? Are you serious?


What?? You don't believe it? Two 15 A breakers would allow you to draw 30 A.


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## brian john (Mar 11, 2007)

BEAMEUP said:


> What?? Are you serious?


Not only is he serious he is CORRECT..

In temporary setups where we are doing bypasses for UPS systems (typically we are replacing the UPS) we do this all the time. 

Though we seldom rely on 2 circuit breakers. as the load sharing usually is not equal.


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## BEAMEUP (Sep 19, 2008)

InPhase277 said:


> What?? You don't believe it? Two 15 A breakers would allow you to draw 30 A.


Oh no, I beleive it. I was just trying to figure out what applacation you would be doing that for since the O.P. was refering to a home & not a business


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## Mr. Sparkle (Jan 27, 2009)

Excuse my ignorance, but can someone clarify what we are talking about here because I look like this -->:blink: after trying to understand what you mean by supplying a single circuit from 2 separate breakers.

Like 2 breakers from the same phase pigtailed feeding 1 wire?


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## Bob Badger (Apr 19, 2009)

Mr. Sparkle said:


> Like 2 breakers from the same phase pigtailed feeding 1 wire?



That would be one way, and if you kept the pigtails equal the current would divide fairly evenly.

The times I have run into it where times someone made a wrong splice in a j-box. Basically they made a 'ring circuit' where you leave a breaker go to all the outlets and back to another breaker on the same phase.


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## Magnettica (Jan 23, 2007)

I run into what Bob said (same phase) occaisonally after a service upgrade. It can frustrating to say the least.


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## BuzzKill (Oct 27, 2008)

thye whole idea sounds ********.


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## smeric28 (Nov 16, 2009)

Bob Badger said:


> Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG) the code prohibits it in Article 240. I think it is 240.8


Thanks that what i needed to know  If it was a snake it would have bit me.

FYI everybody i was answering a diy forum somewhere's else on the internet. and telling the guy it was a bad, very bad idea. i just couldn't find the code section that prohibited it. From what i could gather the guy had a main box and sub box. Sub box had a seperate amp meter. he wanted to run wire to one breaker in the main panel and to one breaker in the sub panel so when he pluged his christmas lights into the circuit he could use the sub box circuit and see how much energy he was using. And then the rest of the year he wanted it to run off the first box.


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## smeric28 (Nov 16, 2009)

BuzzKill said:


> thye whole idea sounds ********.


that's about what i told the guy.


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## brian john (Mar 11, 2007)

BuzzKill said:


> thye whole idea sounds ********.


It is not to ********, in my case we charge typically about 2 to 3 times the going rate, in addition I own most of the CBs and cabling which we rent, for work that often involves paralleling CB's when installing temporary bypasses. My typical customers are electrical contractors, data centers, communication firms and hospitals.


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## BuzzKill (Oct 27, 2008)

brian john said:


> It is not to ********, in my case we charge typically about 2 to 3 times the going rate, in addition I own most of the CBs and cabling which we rent, for work that often involves paralleling CB's when installing temporary bypasses. My typical customers are electrical contractors, data centers, communication firms and hospitals.


 For a temporary set up I'm sure it is fine, but for household use? Idiotic.


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## brian john (Mar 11, 2007)

BuzzKill said:


> For a temporary set up I'm sure it is fine, but for household use? Idiotic.


110% agrement.


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## Roger (Jul 7, 2007)

Bob Badger said:


> Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG) the code prohibits it in Article 240. I think it is 240.8


If the load was in the center of the circuit you could get by with 14 AWG 

Roger


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## BuzzKill (Oct 27, 2008)

brian john said:


> 110% agrement.


 ...and from Bob's article, it is a very common wiring method in Britain! WTF?:no:


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## NolaTigaBait (Oct 19, 2008)

Magnettica said:


> I run into what Bob said (same phase) occaisonally after a service upgrade. It can frustrating to say the least.


This happened to me the other day. I had to add a circuit and all they had was twin ge's. I moved the minis around so that I could add a full size 2pole breaker. I started turning on breakers and ka-pow. Scared the crap out of me. I'm a little confused on the subject as well.


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## BuzzKill (Oct 27, 2008)

NolaTigaBait said:


> I'm a little confused on the subject as well.


 Tell me about it. I hope I never run into one, TS it sounds like a real PITA.


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## NolaTigaBait (Oct 19, 2008)

I just took it off the other breaker and put a wirenut on it. I probably should have found teh problem, or at least marked it. The customer was not going to pay for it.


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## BuzzKill (Oct 27, 2008)

NolaTigaBait said:


> I just took it off the other breaker and put a wirenut on it. I probably should have found teh problem, or at least marked it. The customer was not going to pay for it.


 Well that's the easy way. Even with a circuit tracer you would have to open every device around...yeesh.


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## NolaTigaBait (Oct 19, 2008)

Exactly. There are some real hacks out there.


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> Exactly. There are some real hacks out there.



:sleep1:


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## NolaTigaBait (Oct 19, 2008)

Peter D said:


> :sleep1:


:stupid:


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> :stupid:


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## NolaTigaBait (Oct 19, 2008)

Peter D said:


>


:happybday:


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> :happybday:


sama:


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## NolaTigaBait (Oct 19, 2008)

Peter D said:


> sama:


I see your osoma and raise you a saddam.:saddam:


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## edgarsouthcali (Dec 14, 2009)

whats the point?,It will be pointless to add another breaker when only one can do the job and protect.


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> I see your osoma and raise you a saddam.:saddam:


:surrender:


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## NolaTigaBait (Oct 19, 2008)

Peter D said:


> :surrender:


:sleep1:


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> :sleep1:


:lol:


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## Roger (Jul 7, 2007)

BuzzKill said:


> ...and from Bob's article, it is a very common wiring method in Britain! WTF?:no:


However, the UK ring circuit does not use breakers in parallel.

Roger


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## 480sparky (Sep 20, 2007)

NolaTigaBait said:


> I see your osoma and raise you a saddam.:saddam:


 
WTF is an osoma?


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## NolaTigaBait (Oct 19, 2008)

480sparky said:


> WTF is an osoma?


Bin Laden.....i probably didn't spell it right. Get off my case, Ok?


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## user4818 (Jan 15, 2009)

NolaTigaBait said:


> Bin Laden.....i probably didn't spell it right. Get off my case, Ok?



:sleep1:


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## 480sparky (Sep 20, 2007)

Peter D said:


> :sleep1:


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## Magnettica (Jan 23, 2007)

NolaTigaBait said:


> This happened to me the other day. I had to add a circuit and all they had was twin ge's. I moved the minis around so that I could add a full size 2pole breaker. I started turning on breakers and ka-pow. Scared the crap out of me. I'm a little confused on the subject as well.


What happened was that one of the branch circuits was fed twice downstream from the panel. This technically will work (feeding a branch circuit twice) but only if the two circuits are not on the same leg (for residential) and same phase for a 3-phase panel. This is obviously an incorrect wiring method and it doesn't get detected until circuit breakers are relocated and the existing problem is discovered. Once you turn on that relocated circuit breaker BANG! you're feeding the same circuit twice!


Understand?


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## Grimlock (Aug 4, 2009)

Magnettica said:


> What happened was that one of the branch circuits was fed twice downstream from the panel. This technically will work (feeding a branch circuit twice) *but only if the two circuits are not on the same leg* (for residential) and same phase for a 3-phase panel. This is obviously an incorrect wiring method and it doesn't get detected until circuit breakers are relocated and the existing problem is discovered. Once you turn on that relocated circuit breaker BANG! you're feeding the same circuit twice!
> 
> 
> Understand?


 
You mean as long as the breakers are on the same phase. If they were on opposing phases both breakers would trip, same for Res and Com.


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## Grimlock (Aug 4, 2009)

The problem is easy to fix, just turn that circuit on (just one of the breakers only, nothing else, all other breakers off). Locate the circuit in the house, see what’s on it. Pick a point you feel would be in the middle of the circuit, open a plug or switch (power off) and split the hots. Energize and recheck the circuit to see what was removed. If you are happy with the split then it’s a job well done. 30 minutes to an hour tops, easy fix.


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## NolaTigaBait (Oct 19, 2008)

Magnettica said:


> What happened was that one of the branch circuits was fed twice downstream from the panel. This technically will work (feeding a branch circuit twice) but only if the two circuits are not on the same leg (for residential) and same phase for a 3-phase panel. This is obviously an incorrect wiring method and it doesn't get detected until circuit breakers are relocated and the existing problem is discovered. Once you turn on that relocated circuit breaker BANG! you're feeding the same circuit twice!
> 
> 
> Understand?


Yeah, I do , thats why i said it:thumbsup::thumbsup:


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## NolaTigaBait (Oct 19, 2008)

Grimlock said:


> The problem is easy to fix, just turn that circuit on (just one of the breakers only, nothing else, all other breakers off). Locate the circuit in the house, see what’s on it. Pick a point you feel would be in the middle of the circuit, open a plug or switch (power off) and split the hots. Energize and recheck the circuit to see what was removed. If you are happy with the split then it’s a job well done. 30 minutes to an hour tops, easy fix.


Maybe, but a cheap sob won't pay for that time and i'm not going to find it for free.


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## NolaTigaBait (Oct 19, 2008)

Magnettica said:


> What happened was that one of the branch circuits was fed twice downstream from the panel. This technically will work (feeding a branch circuit twice) but only if the two circuits are not on the same leg (for residential) and same phase for a 3-phase panel. This is obviously an incorrect wiring method and it doesn't get detected until circuit breakers are relocated and the existing problem is discovered. Once you turn on that relocated circuit breaker BANG! you're feeding the same circuit twice
> 
> Understand?


I was talking about not understanding something else. I know the reason why it tripped, it was on the same phase when i moved it.


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## Grimlock (Aug 4, 2009)

NolaTigaBait said:


> Maybe, but a cheap sob won't pay for that time and i'm not going to find it for free.


True, a cheap sob is a cheap sob, especially if you're working on their rental property.


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## cdnelectrician (Mar 14, 2008)

I have seen main breakers in 200 amp Siemens panels that are actually doubled up 100 AMP breakers (2, 100 amp breakers per phase) Pretty common actually, I am sure they are common trip though.


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## Magnettica (Jan 23, 2007)

Grimlock said:


> You mean as long as the breakers are on the same phase. If they were on opposing phases both breakers would trip, same for Res and Com.


Yes, that's what I meant. 

Thank you.


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## RIVETER (Sep 26, 2009)

*Two breakers,*



BEAMEUP said:


> What?? Are you serious?


He is correct, but sometimes, it is the way you say it.Two breakers in parallel, if of the same phase, will allow you to draw double the load before tripping on overload.


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## Droid (Dec 23, 2009)

Bob Badger said:


> Well besides the fact that two over current devices in parallel will supply twice the current. (two 15 amp breakers would require 10 AWG) the code prohibits it in Article 240. I think it is 240.8


You're not supposed to put #10 wire into a 15 amp breaker.


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## Roger (Jul 7, 2007)

Droid said:


> You're not supposed to put #10 wire into a 15 amp breaker.


Why?

It may be an Canadian rule but it is allowed per the NEC and would not be an uncommon installation to compensate for voltage drop.

Roger


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## brian john (Mar 11, 2007)

Droid said:


> You're not supposed to put #10 wire into a 15 amp breaker.


 
There is no logic behind that statement and if it is a local rule then idiots rule.

IF the CB manufacture rates the CB to handle that wire size then it is perfectly legit.


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## gardiner (Sep 25, 2007)

Roger said:


> Why?
> 
> It may be an Canadian rule but it is allowed per the NEC and would not be an uncommon installation to compensate for voltage drop.
> 
> Roger


Its not a Canadian rule as far as I have ever heard and done often due to voltage drop in long runs.


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## Droid (Dec 23, 2009)

*2 breakers, 1 branch cct*



gardiner said:


> Its not a Canadian rule as far as I have ever heard and done often due to voltage drop in long runs.


Yes, that is true about the voltage drop. :thumbsup: In my understanding, a 15 amp bkr is rated for 15 amps. So 2 of them still means 15 amps, but 240 v, if they are not on the same phase. Anyways, you all have a happy Christmas! Andy


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## brian john (Mar 11, 2007)

Droid said:


> Yes, that is true about the voltage drop. :thumbsup: In my understanding, a 15 amp bkr is rated for 15 amps. So 2 of them still means 15 amps, but 240 v, if they are not on the same phase. Anyways, you all have a happy Christmas! Andy


Actually the calculated load on a 15 amp breaker is 15 amps I can put 20 amps on it all day long heck I can put 45 amps on one for 60-90 seconds.



> So 2 of them still means 15 amps, but 240 v, if they are not on the same phase


Depends on the system voltage.
If they are on the same phase the two feeding the same branch circuit will be 30 amps.


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## Roger (Jul 7, 2007)

Droid said:


> So 2 of them still means 15 amps, but 240 v, if they are not on the same phase. Anyways, you all have a happy Christmas! Andy


 
No, as Brian said, two 15 amp breakers in parallel will supply the load with 30 amps and if the load is in the center of the circuit (as stated earlier in the thread) neither breaker or conductor to either of the individual breakers would see more than 15 amps.

Think in basic ohms law and current division.

Roger


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## Mr. Sparkle (Jan 27, 2009)

So hypothetically speaking ....if you needed a 2P30 and all you had was a bunch of SP15's you could indeed piggy one leg on 2 SP15's on A Phase and one leg on 2 SP15's on B Phase and the said equipment would have the same overcurrent rating as if it were on a 2P30 Breaker, correct?


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## Roger (Jul 7, 2007)

Mr. Sparkle said:


> So hypothetically speaking ....if you needed a 2P30 and all you had was a bunch of SP15's you could indeed piggy 2 SP15's on A Phase ans 2 SP15's on B Phase and the said equipment would have the same overcurrent rating as if it were on a 2P30 Breaker, correct?


That is correct and is actually what some main breakers are.

Roger


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## Mr. Sparkle (Jan 27, 2009)

Roger said:


> If the load was in the center of the circuit you could get by with 14 AWG
> 
> Roger


Roger,

By get by you mean it would work, not that it is legal to parallel conductors of that size as per the NEC....correct?


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## Roger (Jul 7, 2007)

Mr. Sparkle said:


> Roger,
> 
> By get by you mean it would work, not that it is legal to parallel conductors of that size as per the NEC....correct?


It would definitely work but the conductors are not the real problem in this scenario, 240.8 is the deal breaker.

If the conductors were the only problem we could get around this when we got up to 1/0 but, if the parallel breakers are not part of a manufactured assembly, it is not a legal installation



> *240.8 Fuses or Circuit Breakers in Parallel.
> *Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.


Roger


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## Droid (Dec 23, 2009)

brian john said:


> There is no logic behind that statement and if it is a local rule then idiots rule.
> 
> IF the CB manufacture rates the CB to handle that wire size then it is perfectly legit.


Yes, you are right!


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## Droid (Dec 23, 2009)

brian john said:


> There is no logic behind that statement and if it is a local rule then idiots rule.
> 
> IF the CB manufacture rates the CB to handle that wire size then it is perfectly legit.


Yes, I agree.


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## Droid (Dec 23, 2009)

brian john said:


> Actually the calculated load on a 15 amp breaker is 15 amps I can put 20 amps on it all day long heck I can put 45 amps on one for 60-90 seconds.
> 
> Yeah, that's true. I'm just used to keeping the current draw under 15 amps. You are absolutely right.
> 
> ...


That's true also, I wasn't thinking of the 2 breakers being on the same phase tho. In fact, I've lost track of the thread!


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