2 branch circuits in a single box

994 Views 20 Replies 11 Participants Last post by OldSparky8, Jun 8, 2020

brian85

Discussion Starter · Jun 4, 2020 (Edited)

I'm replacing the knob and tube in my home and I'd like to have a "double light switch box" (I'm sure there's a better name for that) where each switch is for a light on a different branch circuit. The wiring would be COMPLETELY separate: not sharing neutrals, grounds, etc. I would expect this to be fine (and common!), but since I've never had different circuits (separate breakers) occupy the same box, I thought I'd ask. If this can't be done, then I'll put 2 single light switch boxes right beside one another, but that seems silly.

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seharper

· #2 · Jun 4, 2020

That's fine.

In fact they make boxes with partitions to help with that sort of thing.

You have the right idea re: neutrals.

However, safety grounds can commingle.

Since the devices are on different yokes, the breakers do not need to be handle-tied.

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brian85

Discussion Starter · #3 · Jun 4, 2020

seharper said:
That's fine.

In fact they make boxes with partitions to help with that sort of thing.

You have the right idea re: neutrals.

However, safety grounds can commingle.

Since the devices are on different yokes, the breakers do not need to be handle-tied.

Thank you! Is there a consensus on whether it's better to have the grounds tied together or separate? I've already purchased a standard box, but I can get one with a separator if that's best practice?

rjniles

· #4 · Jun 4, 2020

Not an option, the grounds are required to be connected.

Sent from my RCT6A03W13E using Tapatalk

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chetwisner

· #5 · Jun 4, 2020

Re: sharing neutrals. (If I'm understanding the question correctly) There's no need to run 2 feeders from 2 different breakers, unless you just want to. One 15 or 20 amp breaker can function on two lights with two separate switches. Tie the neutrals together, terminate on each light.

Maybe I misuderstood the OP.

brian85

Discussion Starter · #6 · Jun 4, 2020

chetwisner said:
Re: sharing neutrals. (If I'm understanding the question correctly) There's no need to run 2 feeders from 2 different breakers, unless you just want to. One 15 or 20 amp breaker can function on two lights with two separate switches. Tie the neutrals together, terminate on each light.

Maybe I misuderstood the OP.

I realize that the two lights could be powered by the same feeder, but I want them to be on separate feeders.

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brian85

Discussion Starter · #7 · Jun 4, 2020

rjniles said:
Not an option, the grounds are required to be connected.

Sent from my RCT6A03W13E using Tapatalk

Ok, so the grounds are required to be connected between the two switches even though the two switches only share the same physical space?

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HandyAndyInNC

· #8 · Jun 4, 2020

I've never heard or read that the grounds from separate circuits have to be touching when in the same box. As long as each has a consistent patch back to the panel, it is the same as if they are connected there. I would like to know the reference number.
What you are planning is done all the time. I would label the back side of the cover to indicate such.

chetwisner

· #9 · Jun 4, 2020

HandyAndyInNC said:
I've never heard or read that the grounds from separate circuits have to be touching when in the same box. As long as each has a consistent patch back to the panel, it is the same as if they are connected there. I would like to know the reference number.
What you are planning is done all the time. I would label the back side of the cover to indicate such.

It wasn't said that they HAD to be, it was said that the MAY be. In either case, they should be terminated on the switches.

There's no need to cause confusion here, and create more replies than necessary . The two who replied to him know what they're doing.

Brian: follow Seharper, and rj's advice.

longdrive

· #10 · Jun 4, 2020

Do you necessarily need seperate neutrals? You could use 2 circuits and share a neutral. To each his own i guess.

oldelectricguy

· #11 · Jun 5, 2020

NO! You cannot share a neutral between 2 circuits unless it's a MWBC. You are creating an overloaded neutral situation.

rjniles

· #12 · Jun 5, 2020

HandyAndyInNC said:
I've never heard or read that the grounds from separate circuits have to be touching when in the same box. As long as each has a consistent patch back to the panel, it is the same as if they are connected there. I would like to know the reference number.
What you are planning is done all the time. I would label the back side of the cover to indicate such.

250.148 requires all grounding conductors in a box be connected together.

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seharper

· #13 · Jun 5, 2020

longdrive said:
Do you necessarily need seperate neutrals? You could use 2 circuits and share a neutral. To each his own i guess.

You really, really, really need to separate neutrals from 2 different circuits. Really. Always.

There's no "to each his own" to it; it's not a style thing; crossing separate circuits' neutrals is bad.

I'm not talking about MWBCs.

longdrive

· #14 · Jun 5, 2020

My point was to just use a MWBC.

Jim Port

· #15 · Jun 5, 2020

HandyAndyInNC said:
I've never heard or read that the grounds from separate circuits have to be touching when in the same box. As long as each has a consistent patch back to the panel, it is the same as if they are connected there. I would like to know the reference number.
What you are planning is done all the time. I would label the back side of the cover to indicate such.

This is why you shouldn't be giving advice on an electrical forum.

Reactions: 1

afjes2015

· #16 · Jun 6, 2020 (Edited)

longdrive said:
Do you necessarily need seperate neutrals? You could use 2 circuits and share a neutral. To each his own i guess.

And I'll say it again because it is very dangerous.

NO-this can not be done. Unless this is set up as a MWBC sharing neutrals can cause a neutral overload.

Brian85-Please Google this. You will see how dangerous this is to do sharing neutrals.

Reactions: 1

brian85

Discussion Starter · #17 · Jun 8, 2020

Thanks everyone. Based on the great feedback the two switches will ONLY be connected by their 2 ground wires.

A follow-up, related question: Is it possible that 1 of the 2 circuits in this is 15 amp and the other is 20 amp? To be clear, following the advice in this thread, that would mean that a ground wire from 12-2 romex is connected to a ground wire from 14-2 romex. Nothing else in the two branch circuits would be connected in any way. I expect this is permissible, but I'm not sure whether this is bad practice.

rjniles

· #18 · Jun 8, 2020

All ground wires in a box without regard to wire size or circuit rating must be connected together. So yes the 14 and 12 ground should be connected.

seharper

· #19 · Jun 8, 2020

longdrive said:
My point was to just use a MWBC.

An MWBC is 1 circuit. Hence my confusion.

That seems picayune, but MWBCs are *very* easy to dangerously misconfigure. There's no room for imprecision in MWBCs.

Oldmaster

· #20 · Jun 8, 2020

With arch fault protection sharing neutrals doesn't work. Multi wire branch circuits are 2 circuits sharing 1 neutral.

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