simultaneous tripping

[ox110]

On my jobsite there is talk of a fairly new code that requires the three ungrounded(when working with a three phase system) to trip together when they are sharing a common neutral. I am referring to three seperate circuits that may supply three seperate receptacles. This would require installing a handle tie (if this is acceptable) across the three circuit breakers or using one three pole circuit breaker.

The suggested solution to this is to simply use a seperate neutral for each circuit and continue to use seperate single pole circuit breakers.

I am aware of a requirement that would require all ungrounded conductors to trip together when terminating at a common piece of equiptment, such as a multi pole disconnect switch or when terminating on a common yoke such as a duplex receptacle where the top half would be the black circuit and the bottom half would be the red circuit.

Is anyone aware of this new requiremment. It seems silly for two circuits to trip when there is a overload on just one circuit just because they a sharing the same neutral and if seperat neutrals had to be used there would be much more wire being used plus the size of the raceway would also need to be considered.

 

[ActionDave]

You heard right, and yes it is silly. You can avoid the use of handle ties or a multipole breaker if you run separate neutrals but you need to be careful about pipe fill, box fill, and current carrying conductors in relation to de-rating.

 

[ox110]

Thanks action dave, yes the derating is another issue. Can you direct me as to where I would find this in the NEC and when did this first appear.

 

[templdl]

On my jobsite there is talk of a fairly new code that requires the three ungrounded(when working with a three phase system) to trip together when they are sharing a common neutral. I am referring to three seperate circuits that may supply three seperate receptacles. This would require installing a handle tie (if this is acceptable) across the three circuit breakers or using one three pole circuit breaker. .

Using handle ties will not guarantee that if one breaker trips that its handle will be able to pull the others to the off position.
You have to use a common trip breaker, I.e. a three pole breaker with a common trip which has an internal trip bar connected between all three poles.

 

[curt swartz]

210.4(B)

 

[ActionDave]

210.4(B)

Thanks. I forgot to add this, I was being summoned to supper while I was posting. It first showed up in the '08 code.

 

[texie]

Using handle ties will not guarantee that if one breaker trips that its handle will be able to pull the others to the off position.
You have to use a common trip breaker, I.e. a three pole breaker with a common trip which has an internal trip bar connected between all three poles.

True, but in this case common trip is not required. See 240.15(B)(1) and 210.4(B).

 

[wolfman56]

You're missing the point.
If it is a multi wire circuit, all circuits must simultaneously turn off so there is no chance of getting shocked somewhere down the line because associated conductors could still be live. This recently happened at a service call where there was a multi wire circuit, cable feeding lot lights that we needed to cut. The electrician trusted the property maintenance person when he said he turned off the breaker. He did turn one off and did not know that it involved the breaker next to it also.

 

[texie]

You're missing the point.
If it is a multi wire circuit, all circuits must simultaneously turn off so there is no chance of getting shocked somewhere down the line because associated conductors could still be live. This recently happened at a service call where there was a multi wire circuit, cable feeding lot lights that we needed to cut. The electrician trusted the property maintenance person when he said he turned off the breaker. He did turn one off and did not know that it involved the breaker next to it also.

No, I'm not missing the point. The code only requires identified handle ties in this case and would have prevented the problem you describe. A true common trip is not required and many would argue that it is not desirable either. See 210.4(B) and 240.15(B)(1).

 

[ActionDave]

I would be one of those.

Wolfman, what you described is not a problem with the breaker, it is a problem with the person working on it. Turn off your own breaker off and check with your own meter.

MWBC are not hard to spot, understand, or work on. If you don't know what you are doing, keep you hands off and be humble enough to ask for help.

 

[templdl]

True, but in this case common trip is not required. See 240.15(B)(1) and 210.4(B).

Understood and agree. But the OP refered to simultaneous tripping which I was addressing.

 

[ActionDave]

Understood and agree. But the OP refered to simultaneous tripping which I was addressing.

The OP was asking about a code change that he was unfamiliar with. I doubt he meant simultaneous trip literally.

 

[kwired]

The OP was asking about a code change that he was unfamiliar with. I doubt he meant simultaneous trip literally.

Appropriate response to that may be that simultaneous tripping is not required, simultaneous disconnecting of all poles is.

Unfortuneately if one pole trips there is good chance you will not reset it without turning others off in the process if using handle ties.

 

[templdl]

Appropriate response to that may be that simultaneous tripping is not required, simultaneous disconnecting of all poles is.

Unfortuneately if one pole trips there is good chance you will not reset it without turning others off in the process if using handle ties.

That's true.

 

[ksmith846]

Handle Ties

Handle Ties

Our fix has been to use handle ties for existing panels. We have even had one of our local inspectors allow 6-32 machine screws and nuts to be installed through the hole on the handles. Without looking it up I believe the article mentions "or approved method"....I am not sure but it was accepted that one time around.

I have been ordering my new construction panel boards with 2 and 3 pole 20 amp breakers for the branch circuits. This way we do not have to spend extra money to add the neutrals or use larger conduits. Breakers are nearly free when built into the gear at the factory.

 

[kwired]

Our fix has been to use handle ties for existing panels. We have even had one of our local inspectors allow 6-32 machine screws and nuts to be installed through the hole on the handles. Without looking it up I believe the article mentions "or approved method"....I am not sure but it was accepted that one time around.

I have been ordering my new construction panel boards with 2 and 3 pole 20 amp breakers for the branch circuits. This way we do not have to spend extra money to add the neutrals or use larger conduits. Breakers are nearly free when built into the gear at the factory.

Well if the inspector allows it, then the 6-32 screws are an "approved method". Most of the time the inspector will not allow that though.

Generally purchasing 2 single pole breakers and a handle tie cost more than a double pole breaker. Three pole breakers are not that cheap however - unless you are buying them on an order with the panel as part of a larger purchase

 

[ksmith846]

Just to clarify ...we use handle ties in existing panels where we are reusing the existing single pole breakers.