What Happens When One Ganged Breaker Needs To Trip?

[DerbyDad03]

As most of us know, the tripped position of a circuit breaker is different than the Off position. The tripped position is kind of mid-way between Off and On. We then need to turn the breaker Off and then On to reset it. As far as I know, there is no way for the user to manually set a breaker to the tripped position. The only options a user has is On or Off.

So let's assume we have this (common?) situation:

2 adjacent single pole breakers are tied together with the appropriate tie bar based on the breaker's manufacturer. This is done to ensure that both breakers are always turned off at the same time, killing power to both circuits.

Now let's look at this situation:

One of the circuits has a problem and requires it's breaker to trip. However, that breaker's handle is tied to the adjacent breaker's handle.

What is going to happen when the fault tries to trip the breaker since the adjacent breaker can't be manually set to the tripped position? In other words, how is the tripping force on the rigid tie bar going to deal with the breaker that has no need to trip?

[Ralph Mowery]

The purpose of the tie bar is to cut off the breaker on the side that is not tripped. In other words, in effect both will either be tripped or atleast in an off position.

[dpb]

On 4/5/2014 8:56 AM, DerbyDad03 wrote: ...

It doesn't--the trip mechanism doesn't require movement--it's a corollary event the result of the tripping. The other will remain as is; flipping them both down and back on will reset.

It's a UL reqm't that a tied breaker can't not trip owing to the tie.

[gfretwell]

The breaker will trip internally, even if the handle is held in the on position. That is why you have to turn them all the way off to reset it. It is the reason why handle ties do not meet all the code issues for some types of circuits. They need to use a real multi pole breaker that trips all circuits.

Essentially handle ties are only OK if you are using this as a disconnect on multiwire circuits, not overcurrent protection for line to line loads.

[dpb]

That is, to be perfectly clear--the effect of the tie on tripping is immaterial and the breaker functions as if it weren't there. It doesn't even try to move the other one; not it's job.

[DerbyDad03]

Thanks to all for the same answer. Glad to see that there is consensus. ;-)

Next question: the reason for these tied breakers is that there is a bathroom with a fan/heater/light combo unit. The fan/heater are on one 20A breaker. The other 20A breaker feeds a GFI and the light in the combo unit as well as a can light over the shower stall are fed from the load side of the GFI.

The GFI eliminates the danger from the light fixture over the shower and the ganged breakers ensure that the entire fan/heater/light unit is dead since it kills both circuits at the same time.

Do you see anything wrong with this setup?

[trader_4]

Personally, I would have just put the light in the fan/heater/light fixture on the same circuit as the fan/heater with one breaker. Then just use a second breaker for the GFCI and shower light. That way you have one breaker for the fan/heater/light, one for the GFCI receptacle and shower light, and no need to tie them together.

[Pete C.]

The handle tie is for manual control and visual purposes (QO breakers have a single handle regardless of poles). There is an internal common trip mechanism.

[dpb]

On 4/5/2014 10:37 AM, trader_4 wrote: ...

Nothing "wrong" with it per Code, but I'd've gone trader's route, too.

[DerbyDad03]

It's been setup that way for a long time and I doubt the homeowner is going to change it now, but I agree that it might have made sense to use one breaker for the FHL unit and the other for the GFI/light.

Thanks again.

[clare]

GENERALLY the second braker will trip to the off position. Because it is an ambiguous condition, it is PREFERRED to use a twinner breaker rather than linking 2 standard breakers for that application (like a

220 breaker). They are built to trip together.

[clare]

Use a double pole breaker and you are fine. Mechanically linking 2 separate breakers may be an issue, sunctionally, or in code, or both.

[bud--]

Fine as is.

If the circuits have a common neutral the breakers for the 2 circuits need a handle tie so there is a common disconnect. That is another reason why a handle tie was used. (That requirement was added relatively recently.)