Dbl Pole Ganged Breaker Q

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FionaZuppa

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AZ
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Part Time Electrician (semi retired, old) - EE retired.
does NEC prohibit using the poles from a dbl-pole ganged breaker as independent circuits, say one side out to some outlets, the other side to some lighting? in this example lets just say each circuit is using 14/2 wire.

Eaton says doing such and the breaker may not trip as designed.

so what happens in case of a 220v oven that uses 120v tap for light? is this use ok?
 

mopowr steve

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NW Ohio
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Electrical contractor
I can't think of any reason that it would not be allowed after all code states that multi-wire branch circuits (which are 2 individual circuits just sharing neutral) are now to be attached to breakers that are handle tied or common trip double pole. May not be best design choice but should be OK.
As far as Eaton comment doesn't affect trip condition only may present unwanted result to have lights shut off when there is a short/overload on receptacle circuit.
 
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Dennis Alwon

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If you have a multiwire branch circuit then you would be required to use a dp breaker or 2 sp breakers with breaker ties.
 

FionaZuppa

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AZ
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Part Time Electrician (semi retired, old) - EE retired.
ok, from electrical view seems like in some cases its ok. but if Eaton says "not a recommended use of our dbl-pole ganged breaker" then by NEC rules you cant use it for two 120v circuits.

so there is other chatter out there that suggests a tru dbl-pole breaker has it's trip profile defined under balanced load. is this true? Eaton seems to suggest that.
 

iwire

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Location
Massachusetts
ok, from electrical view seems like in some cases its ok. but if Eaton says "not a recommended use of our dbl-pole ganged breaker" then by NEC rules you cant use it for two 120v circuits.

so there is other chatter out there that suggests a tru dbl-pole breaker has it's trip profile defined under balanced load. is this true? Eaton seems to suggest that.

There is no prohibition against using one pole of a multipole breaker.

Easton's recommendation is not part of the listing or labeling so that would not fall under 110.3(B).
 

don_resqcapt19

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I assume that the recommendation is pre 210.4(B). I expect the idea was based on a fault on one circuit resulting in the loss of power to both circuits.
 

FionaZuppa

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AZ
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Part Time Electrician (semi retired, old) - EE retired.
I assume that the recommendation is pre 210.4(B). I expect the idea was based on a fault on one circuit resulting in the loss of power to both circuits.

although Eaton did mention this as a pitfall, Eaton did say that the "trip" is different if its just one side going into overload. i guess my answer is within the real technical details on how the ganged dbl-pole breaker work.
 

Dennis Alwon

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although Eaton did mention this as a pitfall, Eaton did say that the "trip" is different if its just one side going into overload. i guess my answer is within the real technical details on how the ganged dbl-pole breaker work.


This does not make sense. If I short out one leg of a 240 v circuit then they are saying that a dp breaker will not trip as it should???? I don't think so
 

growler

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Location
Atlanta,GA
does NEC prohibit using the poles from a dbl-pole ganged breaker as independent circuits, say one side out to some outlets, the other side to some lighting? in this example lets just say each circuit is using 14/2 wire.

Eaton says doing such and the breaker may not trip as designed.

so what happens in case of a 220v oven that uses 120v tap for light? is this use ok?

I can't think of any reason that it would not be allowed after all code states that multi-wire branch circuits (which are 2 individual circuits just sharing neutral) are now to be attached to breakers that are handle tied or common trip double pole.


If the breaker doesn't trip as designed that's Eaton's problem and not mine.


The truth is I don't think all the people at the customer service department for these manufacturers know as much as they should. If you can call and ask to talk to a more experienced engineer ( Eaton rep.)
 

FionaZuppa

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Location
AZ
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Part Time Electrician (semi retired, old) - EE retired.
This does not make sense. If I short out one leg of a 240 v circuit then they are saying that a dp breaker will not trip as it should???? I don't think so
not in those words, but yes. one pole in overload has different trip profile than balanced two pole overload..... so Eaton tech person said. i asked for technical details via Eaton online form submission.


If the breaker doesn't trip as designed that's Eaton's problem and not mine.


The truth is I don't think all the people at the customer service department for these manufacturers know as much as they should. If you can call and ask to talk to a more experienced engineer ( Eaton rep.)

Eaton says their ganged dbl pole is not meant to be used as two single poles and that its not recommended to use them that way. if the UL rating says otherwise than so be it, but as of now i am only going by what Eaton has told me.
 
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FionaZuppa

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Location
AZ
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Part Time Electrician (semi retired, old) - EE retired.
It makes no sense and I think whoever told you that from Eaton is entirely mistaken.

If not that would be dangerous.

this sparked my interest, i got a tad further with Eaton support. now they say that the trip profile, be it two full circuits or just one dbl-pole circuit, remains the same (some minor caveats, but an allowed use).
 

FionaZuppa

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Location
AZ
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Part Time Electrician (semi retired, old) - EE retired.
so, if you go look at the time/current charts for the breakers it notes the following:

"... tested in open air with current in all poles."
and
"... RMS symmetrical amperage ..."

so, although we expect an overload in one pole to trip to same graph, i dont see where Eaton shows that data, they test with current in all poles and balanced.

is their testing incorporated into the UL listing for the device?
 

iwire

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Location
Massachusetts
A very common use of a two pole circuit breaker is to supply multi wire branch circuits.

Consider supplying a duplex receptacle with that circuit that has been split.

Is it your postion that one of the receptacles is under protected?
 

Smart $

Esteemed Member
Location
Ohio
so, if you go look at the time/current charts for the breakers it notes the following:

"... tested in open air with current in all poles."
and
"... RMS symmetrical amperage ..."

so, although we expect an overload in one pole to trip to same graph, i dont see where Eaton shows that data, they test with current in all poles and balanced.

is their testing incorporated into the UL listing for the device?
I suspect the breaker(s) you are discussing are common trip design rather than independent trip. JMO, independent trip is a better design choice for MWBC's... but as mentioned, Code does not prohibit a common trip breaker.
 

FionaZuppa

Senior Member
Location
AZ
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Part Time Electrician (semi retired, old) - EE retired.
I suspect the breaker(s) you are discussing are common trip design rather than independent trip. JMO, independent trip is a better design choice for MWBC's... but as mentioned, Code does not prohibit a common trip breaker.

yes, a std common trip dbl-pol breaker. the question is based around an existing common trip. as example, the stove is using a 50amp 220v dbl-pole common trip breaker. i now remove the stove and want to use the poles, so i bring in two 8/2 wires, one for a new bedroom outlet, and one for a new livingroom outlet, i then use one pole of the dbl-pole breaker for each circuit. my example is bad, but you get the point.

why? so i can re-use the dbl-pole breaker.
 
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Smart $

Esteemed Member
Location
Ohio
yes, a std common trip dbl-pol breaker. the question is based around an existing common trip. as example, the stove is using a 50amp 220v dbl-pole common trip breaker. i now remove the stove and want to use the poles, so i bring in two 8/2 wires, one for a new bedroom outlet, and one for a new livingroom outlet, i then use one pole of the dbl-pole breaker for each circuit. my example is bad, but you get the point.

why? so i can re-use the dbl-pole breaker.
I agree... bad example. :happyyes:

As already mentioned, Code does not prohibit using a common-trip breaker for a MWBC.
 

charlie b

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Lockport, IL
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. . . after all code states that multi-wire branch circuits (which are 2 individual circuits just sharing neutral) are now to be attached to breakers that are handle tied or common trip double pole.
The code says no such thing! :happyno:

OK, everyone take a few moments to let the shock value of that assertion pass over you. :cool:

What the code says is that there must be a means for simultaneously disconnecting all ungrounded conductors at the point at which the circuit originates. We have made the practical choice of achieving this disconnection by one of the two methods you list. But the code does not tell us we must use one of them, nor does it forbid us from finding another method.

From a purely technical perspective, I would want to know what changes in the breaker's trip characteristics when we share a neutral as opposed to providing separate neutrals. Consider, for example, a MWBC that serves two loads, one of which is turned off at the present moment. The other is running, and the shared neutral carries all the current of that load's ungrounded conductor. This is exactly the same situation you get with two completely different circuits, each with its own neutral, each serving one load, and with one of those loads not running at the present moment. Now cause either an overload or a short circuit condition on the one load that is running. How does the breaker behave? How would the breaker behave differently if the second load were running in the MWBC configuration? How would the breaker behave differently if the second load were running in the separate circuit configuration?

My inclination is to suspect that the breaker will behave in exactly the same manner in all cases. But I have no facts to offer. This is the way I would want the issue presented to Eaton.

 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.

From a purely technical perspective, I would want to know what changes in the breaker's trip characteristics when we share a neutral as opposed to providing separate neutrals. Consider, for example, a MWBC that serves two loads, one of which is turned off at the present moment. The other is running, and the shared neutral carries all the current of that load's ungrounded conductor. This is exactly the same situation you get with two completely different circuits, each with its own neutral, each serving one load, and with one of those loads not running at the present moment. Now cause either an overload or a short circuit condition on the one load that is running. How does the breaker behave? How would the breaker behave differently if the second load were running in the MWBC configuration? How would the breaker behave differently if the second load were running in the separate circuit configuration?

My inclination is to suspect that the breaker will behave in exactly the same manner in all cases. But I have no facts to offer. This is the way I would want the issue presented to Eaton.


why do you think shared neutral makes it different? i was curious about common trip dbl-pole breaker ganged breaker showing different trip characteristics between balanced and unbalanced loads up to trip. Eaton (by phone) yesterday recommended that such breaker not be used in such a way, but that didnt seem right. Eaton (by phone today) suggested that the trip profile should remain the same but the consequence is that you trip the other circuit (which is required in some wiring schemes, and not required in others).

that noted, the Eaton time/trip profile graphs make note that it is "all poles" and "symmetric" current. if this is the only test data available then i dont see a way to argue my question as there is no data to show what unbalanced loads do to the trip profile, etc.

that said, w/o such data and NEC allows MWBC shared neutral via common trip dbl-pole breaker, then perhaps there's a gap to be answered?
 
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