New Build - Outlets along wall - alternate circuits?

[mm08822]

OK but usually we now use GFCI recepts for economy rather than breakers...

So am I correct what I am saying that sure he can run a 12/3 to the first 1900 w two GFCI recepts... but the he CANNOT continue down the wall w a 12/3?

Correct?

Marc

Depends on the GFCI breaker style used.

If a 120/240v rated gfci cb is used - basically a 3 wire version, it will monitor both hot legs and the neutral together. It also has the downside of both ckts tripping together regardless of which ckt had the fault.

I would skip the MWBC, run conduit and 4 wires - 2 independant ckts.

Here's a link you can reference:
https://download.schneider-electric..._Name=48840-058-03.pdf&p_Doc_Ref=48840-058-03

Refer to figure #2

 

[Marctrees]

HMMM. fig #2 very interesting.

So what I think I understand is - IF he used this GFI BREAKER... he COULD continue down the wall using 12/3 ?

But if he used two separate GFI DEVICES, like in my paragraph quoted in post #41..then he could not.

The load side downstream neutrals would have to be isolated from each other.

Yes ?

Apparently the GFI Breaker somehow in it's brain like seperates the neutral to check "in and out " load PER "Phase" side ??

Marc

 

[Marctrees]

My brain is jumbled.

I think it all goes back to the "neutral carries only the unbalanced load" somehow but I can't grasp it.

I still say he cannot run 12/3 w a shared neutral down the wall from TWO GFI devices if his home run first hits two GFI recept's. and then he runs 12/3 downstream to standard recept's protected by the TWO "load" sides.

Marc

Marc

 

[mm08822]

HMMM. fig #2 very interesting.

So what I think I understand is - IF he used this GFI BREAKER... he COULD continue down the wall using 12/3 ? Yes, 120/240v, 3 wire version needed. This is different than a 120v 2wire version and a 240v 2wire version.

But if he used two separate GFI DEVICES, like in my paragraph quoted in post #41..then he could not. Correct

The load side downstream neutrals would have to be isolated from each other.

Yes ? Yes

Apparently the GFI Breaker somehow in it's brain like seperates the neutral to check "in and out " load PER "Phase" side ??

Marc

The "brain" is simply what conductors run through the donut (coil) in the gfci. As long as the net sum of currents passing thru it is less than 6 ma, it won't trip.

 

[mm08822]

My brain is jumbled.

I think it all goes back to the "neutral carries only the unbalanced load" somehow but I can't grasp it.

I still say he cannot run 12/3 w a shared neutral down the wall from TWO GFI devices if his home run first hits two GFI recept's. and then he runs 12/3 downstream to standard recept's protected by the TWO "load" sides.

Marc

Marc

We are saying the same thing. It will not work with two seperate gfci devices. It all needs to be done by 1 gfci device measuring L1,L2 and N simultaneously.

 

[Marctrees]

mm - "The "brain" is simply what conductors run through the donut (coil) in the gfci. As long as the net sum of currents passing thru it is less than 6 ma, it won't trip."

That should be worded differently, but I do understand what you are getting at.

Makes sense.

Texting or email is sometimes not as clear as in person back and forth.

Marc

 

[Marctrees]

We have fun and major learning here.

Thank you GJ for the Forum !!!!

Marc

 

[thoyer]

We have fun and major learning here.

Thank you GJ for the Forum !!!!

Marc

Very constructive thread - thank you everyone!

Tom

 

[exranger06]

HMMM. fig #2 very interesting.

So what I think I understand is - IF he used this GFI BREAKER... he COULD continue down the wall using 12/3 ?

But if he used two separate GFI DEVICES, like in my paragraph quoted in post #41..then he could not.

The load side downstream neutrals would have to be isolated from each other.

Yes ?

Apparently the GFI Breaker somehow in it's brain like seperates the neutral to check "in and out " load PER "Phase" side ??

Marc

Correct. If he were to use GFCI receptacles, he would have to run two neutrals, one for each circuit, and couldn't use 12/3. The other option is to use a 2-pole GFCI breaker, and then he could use 12/3.

Another option is to use a non-GFCI breaker, use 12/3 and just install a GFCI receptacle at every location. Connect wires only to the LINE side of every receptacle. Not very cost effective, just sayin' it's an option.

 

[kaffine]

There is also 12-2-2 NM cable that has 2 hots and 2 neutrals although from what I have seen it costs more than 2 runs of 12-2.

 

[ddawg16]

I'm not a fan of MWBC's. In relative terms....wire is cheap. Unless it's a really long run, I don't see a big savings.

Besides, who wants to loose all power when only one side trips?

 

[sberry]

You can use 2 gfci on a multi wire, its done all the time. It's done at the point you create 2 circuits. The electric service is one big version of a multi wire. Neutral makes a Y and goes to each device
I got one where I e is gfci and one goes to a common duplex.

 

[Marctrees]

Yes... but to feed farther recepts the neutrals need to be isolated... hence 4 cond needed.. 3 will not do it.

The OP wanted to use 12/3 down the wall.. presumably feeding "load" side rercepts.

I was saying that THAT would not work.

Marc

 

[dave*99]

I have some receptacles in the ceiling. For the following:
Trouble light with retractable cord reel
Extension cord with retractable cord reel
Remotely controlled light for garage door opener
Garage door openers
And a junction box to power the lift
I also have a ceiling fan box
Take a good look at the ceiling and plan accordingly.

 

[pjmariner]

I ran MWBC using 12/3, I have 2 pole 20amp GFCI, the breaker was pricey at $90 for my panel, but i ran a total of 19 4 square boxes in the garage with 38 outlets total, so i saved money being able to use common outlets.

Each box has an outlet from each circuit, one outlet white one outlet almond so i can tell at a glance what circuit i am on to keep vacuum and tool on separate circuits. I pre-wired and pigtailed all outlets in the outlet covers and used wagos at the box, made installation very easy. I have outlets strategically placed in cabinets, on bench fronts, in ceiling, and along walls, etc. You can see it in my build here for more detail, most electrical starts on page 2

https://www.garagejournal.com/forum/showthread.php?t=397592&page=2

 

[dscheidt]

I'm not a fan of MWBC's. In relative terms....wire is cheap. Unless it's a really long run, I don't see a big savings.

Besides, who wants to loose all power when only one side trips?

If you deal with conduit, MWBC are a big saver. Three wires for two circuits, instead of four, and only two current carrying wires. Keeps the conduits near the panel cleaner.

It's also a 240 V circuit, so the voltage drop is lower. That can save having to increase conductor size, which saves more copper (and money).

 

[sberry]

I am not immune, ran 4 circuits a while back where 2 would have done. The wire wasn't much but 2 breakers and a gfci extra. Another 4 inch box and a cover too.