GFCI protection on a MWBC

[ticklechicken]

I have a MWBC with several 120 and 240 receptacles scattered along the circuit. The 120 receptacles are wired to each hot leg of the MWBC. I'm trying to figure out how to add GFCI protection to this. I would prefer to just add a GFCI breaker like this one, a 20 amp QO breaker.

Will this breaker protect both the 120 circuits?
If I'm using the 120 and 240 receptacles at the same time, will the GFCI trip?
If I'm using the 120 and 240 receptacles at the same time, will the 120 receptacles be GFCI protected?
Any thing else to be worried about?

The research that I've done warns about using a GFCI breaker like this. I've learned that a GFCI trip will take out both legs of the MWBC, but I don't think that would be a big deal for this application.

 

[wyliesdiesels]

I have a MWBC with several 120 and 240 receptacles scattered along the circuit. The 120 receptacles are wired to each hot leg of the MWBC. I'm trying to figure out how to add GFCI protection to this. I would prefer to just add a GFCI breaker like this one, a 20 amp QO breaker.

First off where is this circuit located?

Second what brand and model panel do you have?

And third what is this circuit powering?

You mentioned 240v outlets....

Since this is a MWBC, your only choice is to use a double pole breaker since there is no such thing as a 240v GFCI outlet.

1. Will this breaker protect both the 120 circuits?

2. If I'm using the 120 and 240 receptacles at the same time, will the GFCI trip?

3. If I'm using the 120 and 240 receptacles at the same time, will the 120 receptacles be GFCI protected?

4. Any thing else to be worried about?

1. yes why wouldnt it?

2. It would only trip if there is a ground fault with current leaking outside the circuit. Im not sure why you would be questioning if it would trip when youre using 120v and 240v outlets. Perhas you dont understand how a GFCI functions?

3. see #1

4. what is this circuit powering?

The research that I've done warns about using a GFCI breaker like this.

Where did you read that and what was the warning?

I've learned that a GFCI trip will take out both legs of the MWBC, but I don't think that would be a big deal for this application.

Yes thats correct because the GFCI will open all ungrounded conductors to protect persons...

 

[rlitman]

Take a look here:
http://www.schneider-electric.us/en/faqs/FA115047/

That breaker has a neutral wire that goes to the panel neutral bar, and then in your MWBC you connect your neutral to the neutral position in the breaker.

It is able to do everything you want.

 

[ticklechicken]

First off where is this circuit located?

Second what brand and model panel do you have?

And third what is this circuit powering?

Perhaps you dont understand how a GFCI functions?

Where did you read that and what was the warning?

1. Detached garage
2. Square D QO
3. Various small woodworking tools

I don't

I don't exactly remember. Some google searches that led me to GJ, Mike Holt, and a few other forums. The main warning was that any fault would trip both 120 legs of the 240 breaker.

Take a look here:
http://www.schneider-electric.us/en/faqs/FA115047/

That breaker has a neutral wire that goes to the panel neutral bar, and then in your MWBC you connect your neutral to the neutral position in the breaker.

It is able to do everything you want.

Thanks for the link.

 

[sberry]

You have 120 and 240 on the same circuit? I know I will catch **** for saying this because in some cases this could be all code legal but it really isn't always a great idea in home garages. I can do this type of thing but don't always complicate it as much as I can unless there is a real technical reason to do it or there are some big savings.
I use 120 circuits and 240 and don't always use mwbc unless there are pipe fill issues, on occasion work can be done with a single cable especially with long runs. My Grandmothers kitchen counter top had a single 15A that was tied in with other stuff, it really wasnt a problem but a new micro tripped it so I ran 2 new 20's for it. While its tempting to jbox it and get fancy the reality was a 5 foot wire savings over simply home running it to the panel.
In residential garages its just confusing for the next guy and doesn't let one disconnect a single circuit at a time or let them use common cfci outlets.
I had to replace a gfci single pole breaker in a neighbors a bit ago, I forget what it costs, didn't stock it and it would have been only slightly more work for the installer at the time to simply add another outlet and use a common part.
As was mentioned in the first post which says a lot,,, searching forums, google searches, etc to wire a simple circuit where there is an easier and more practical way.

 

[mm08822]

Take a look here:
http://www.schneider-electric.us/en/faqs/FA115047/

That breaker has a neutral wire that goes to the panel neutral bar, and then in your MWBC you connect your neutral to the neutral position in the breaker.

It is able to do everything you want.

I searched that part number various ways for 30 mins last night and could not find a connection diagram to confirm whether the neutral pole was present.

What did you search with to get that link?

 

[rlitman]

I searched that part number various ways for 30 mins last night and could not find a connection diagram to confirm whether the neutral pole was present.

What did you search with to get that link?

Yeah, I ran into that same wall. Then I had a crazy idea. Search for "how does a gfci breaker work", and it was the first link from a manufacturer.

 

[mm08822]

Yeah, I ran into that same wall. Then I had a crazy idea. Search for "how does a gfci breaker work", and it was the first link from a manufacturer.

Well good find. That's one to keep as I cant say I have used 120/240v versions before.

And the OP's application is a little unique.

 

[rlitman]

Well good find. That's one to keep as I cant say I have used 120/240v versions before.

And the OP's application is a little unique.

I have not run into that either, and yeah, I too would think it is pretty unique, though not at all unreasonable.

 

[Zeke]

You have 120 and 240 on the same circuit? I know I will catch **** for saying this because in some cases this could be all code legal but it really isn't always a great idea in home garages. I can do this type of thing but don't always complicate it as much as I can unless there is a real technical reason to do it or there are some big savings.
I use 120 circuits and 240 and don't always use mwbc unless there are pipe fill issues, on occasion work can be done with a single cable especially with long runs. My Grandmothers kitchen counter top had a single 15A that was tied in with other stuff, it really wasnt a problem but a new micro tripped it so I ran 2 new 20's for it. While its tempting to jbox it and get fancy the reality was a 5 foot wire savings over simply home running it to the panel.
In residential garages its just confusing for the next guy and doesn't let one disconnect a single circuit at a time or let them use common cfci outlets.
I had to replace a gfci single pole breaker in a neighbors a bit ago, I forget what it costs, didn't stock it and it would have been only slightly more work for the installer at the time to simply add another outlet and use a common part.
As was mentioned in the first post which says a lot,,, searching forums, google searches, etc to wire a simple circuit where there is an easier and more practical way.

I had the same thought. Does not sound right. He couldn't, shouldn't have more than a 20 amp breaker. What's the point of 240v on a 20 amp breaker? Some dual voltage compressors would work on that, but your typical 240 table saw needs a 30 amp min.

 

[ticklechicken]

Well good find. That's one to keep as I cant say I have used 120/240v versions before.

And the OP's application is a little unique.

I read a few threads where they were discussing 120/240 versions and 240 versions. I never understood the difference, but I did read that a 120/240 version is what would be needed for what I'm trying to do. I'm a little fuzzy on my recollection, but I think it was stated that only the QO breakers are the 120/240 version.

What is the difference between 120/240 versions and 240 versions? If I'm holding a breaker, how do I determine what type it is?

 

[ticklechicken]

I had the same thought. Does not sound right. He couldn't, shouldn't have more than a 20 amp breaker. What's the point of 240v on a 20 amp breaker? Some dual voltage compressors would work on that, but your typical 240 table saw needs a 30 amp min.

I have five woodworking tools that use 20 amp 240v breakers.

 

[rlitman]

I read a few threads where they were discussing 120/240 versions and 240 versions. I never understood the difference, but I did read that a 120/240 version is what would be needed for what I'm trying to do. I'm a little fuzzy on my recollection, but I think it was stated that only the QO breakers are the 120/240 version.

What is the difference between 120/240 versions and 240 versions? If I'm holding a breaker, how do I determine what type it is?

The 120/240 version must have two terminals for the hot line wires, and another terminal for the load neutral, plus a neutral wire that goes to the neutral bar.

If there is a white neutral wire, but no place to connect a neutral wire from the load, then it would be 240 only.