lighting circuit wiring: shared neutral

[rjacobs]

Im getting confused reading about shared neutrals, MWBC(I dont think this is what I am trying to do as I only want/need to use a single breaker), etc...

Getting my plan together to install my shop lighting... Somebody sanity check me or call me an idiot(cause I likely am).

-10x 4' LED strip lights
-2x LED exterior overhead door lights
-1x LED exterior man door light

I am trying to minimize my EMT runs and make everything look clean. Also trying to minimize wire usage and keep to 3/4 EMT.

Want to do this on a single 15a or 20a CB with 3 Lutron Caseta switches. Pulling #12 THHN in 3/4 EMT.

My terminology is probably not correct as I am a rank amateur.
If I read the NEC correctly I can run a shared ground and neutral on this entire circuit because they will all be in the same conduit/raceway, but each "branch" needs its own dedicated load wire(obviously, otherwise no way to control each bank of lights). From what my brain is telling me after reading a bunch of articles on this is I take my feed from the CB and wire all grounds and neutrals together(5 wires: 1x feed, 3x switches, 1x circuit run) and then pull a single ground and neutral wire through the whole setup and wire each light from there... Then I pull 3 load wires, one for each of my light circuits.

Am I out to lunch on this or is this method acceptable? If not I can just pull more wire, I believe I can fit 10x #12's in a 3/4 EMT so not a problem there as I would end up with 9 wires(3 wires x 3 light circuits)...

 

[PCustoms]

I'm lost....

3 wires from panel to box with switches (could run 2 if using conduit as ground).

3 wires to each light bank

At the switch box, Tie all neutrals to each other, then tie all ground together. The Hot from panel goes to all switches, then the hot to each light bank goes to the other side of the corresponding switch.

3/4 EMT is overkill. #12 is probably overkill, I doubt you need 20A for those lights but would have to check the math.

 

[theoldwizard1]

First off, #12 is a waste of money for a "lighting" circuit. Heck, IMHO #12 is a waste of money for all 120VAC circuits, except where specifically required by the NEC !

Run a "main" conduit (NM-b) from the load center to the farthest load (fixture). Working backwards add a Jbox where you need to split off the hot for a switch for that load, This could be the switch box itself.

Continue working backward, but the previous box will require you to cut/split the hot. Again this could be in the switch box or a separate Jbox. The incoming hot from the load, will have a hot leg going to the switch and a hot leg going forward. How you get the neutral and ground to the light fixture is another issue.

 

[mm08822]

This is too much jumping the gun. Provide a floor plan with lighting and switch(es) location(s) and panel. THEN we can discuss what the possibilities are. 1/2" emt is probably fine, but again, details first.

MWBC are for 2 cb's on opposite "phases". If you are feeding everything from 1 cb, then that is not a MWBC. Splitting a neutral because the hot wire is interrupted due to switches is not a mwbc.

 

[dscheidt]

To answer the question, you don’t need to run a neutral with each switch leg, one per pipe is fine. You don’t need a separate ground in emt.

 

[rjacobs]

my city requires #12 in each branch circuit... dont ask me why... had this discussion in another thread last week or week before. dont need to beat that dead horse again.

20a cb is more than is needed, dont disagree, but I have 2 extra's that came with my CB panel, so might as well use them, they are free.. 15a is fine. I think my load calc would be less than 10a if every light was on.

Im running 3/4 EMT only because of how my j-box's are, they have a 3/4 knockout centered on 2 sides. Ill T off of them to each light with 1/2 EMT as the other 2 sides center of the box has 1/2 knock outs...

 

[rjacobs]

This is too much jumping the gun. Provide a floor plan with lighting and switch(es) location(s) and panel. THEN we can discuss what the possibilities are. 1/2" emt is probably fine, but again, details first.

MWBC are for 2 cb's on opposite "phases". If you are feeding everything from 1 cb, then that is not a MWBC. Splitting a neutral because the hot wire is interrupted due to switches is not a mwbc.

I already provided a lighting plan in another thread.

Yea I was reading on MWBC's and thought "ok i think I understand" then as I read more I was like "no im not doing that, im only using 1 leg, not 2".

 

[rjacobs]

Run a "main" conduit (NM-b) from the load center to the farthest load (fixture).

I was under the impression you cant pull romex through EMT its got to be individual THHN. Anyway I already have spools of THHN so thats going in.

 

[mm08822]

Should have kept it all in the same thread.

Most respondents dont have time, energy, or memory(?) to concatinate your separate details.

 

[rjacobs]

Should have kept it all in the same thread.

Most respondents dont have time, energy, or memory(?) to concatinate your separate details.

because my lighting layout has about zero to do with my question above... I believe @dscheidt answered the question though.

 

[dave*99]

I'm lost....

3 wires from panel to box with switches (could run 2 if using conduit as ground).

3 wires to each light bank

Tie neutral and ground together at the box. Hot goes to the switch, then onto each light bank.

3/4 EMT is overkill. #12 is probably overkill, I doubt you need 20A for those lights but would have to check the math.

I believe you mean tie all the neutrals together and tie all the grounds together - but for the sake of clarity to those less experienced, you may want to edit that sentence.

 

[PCustoms]

I believe you mean tie all the neutrals together and tie all the grounds together - but for the sake of clarity to those less experienced, you may want to edit that sentence.

Good call.

The reality is (as I'm sure you know) there's a ton of variations on how this could be done based on how he wants to pull wire. But power at the switch is usually the simpler explanation, and shows there's only need for 2-3 wires from the panel, certainly not the 9 mentioned in OP

 

[Shiftless]

Remember that a neutral is required in each switch box.
Although 1/2 inch conduit is adequate, pulling multiple 12 ga. wires will be easier with 3/4 especially if there are a few bends.

edit: An exception to that rule is that if your wiring is in conduit and there is room to pull another wire in the future, you don’t need to supply a neutral wire in those boxes.

 

[cgrutt]

Not sure if there are multiple entry ways or not but may want to consider and/or need to pull additional wire(s) for 3-way circuits, if any, so you can turn lights on and off from each entry. Agree its just three wires from panel to 1st junction box.

 

[Shiftless]

Not sure if there are multiple entry ways or not but may want to consider and/or need to pull additional wire(s) for 3-way circuits, if any, so you can turn lights on and off from each entry. Agree it’s just three wires from panel to 1st junction box.

I don’t think it‘s an actual requirement to have 3 way switches at each entry door, but it is certainly convenient. If the project is being inspected, the local inspector may insist on 3 ways if there is more than one door. My local inspector insisted on 3 ways when I added an outside door to one of our bathrooms. No point in arguing. But for the record, I have NEVER gone through the garden gate, walked 50 feet and entered the house at night through the hall bathroom door that opens into the back yard.

 

[cgrutt]

I don’t think it‘s an actual requirement to have 3 way switches at each entry door, but it is certainly convenient. If the project is being inspected, the local inspector may insist on 3 ways if there is more than one door. My local inspector insisted on 3 ways when I added an outside door to one of our bathrooms. No point in arguing. But for the record, I have NEVER gone through the garden gate, walked 50 feet and entered the house at night through the hall bathroom door that opens into the back yard.

I wasn't necessarily thinking code more convenience/safety no fun walking through a dark garage to get to a light switch. I'd have at least one lighting circuit on a three way if for example there are both interior and exterior doors. Anyway comment was more for thinking about number of wires needed when he pulls them.

 

[dave*99]

I was under the impression you cant pull romex through EMT its got to be individual THHN. Anyway I already have spools of THHN so thats going in.

Pulling NM-b through conduit is not prohibited provided you conform to fill requirements. Conduit is sometimes used to protect part of a NM-b run where it could be exposed to damage. But it would be foolish to do it on your project.

 

[rjacobs]

Good call.

The reality is (as I'm sure you know) there's a ton of variations on how this could be done based on how he wants to pull wire. But power at the switch is usually the simpler explanation, and shows there's only need for 2-3 wires from the panel, certainly not the 9 mentioned in OP

I never said I WANTED to pull 9 wires, but if every one of my light circuits(3) require all 3 wires pulled(hot, neutral, ground) thats 9 wires...unless my math doesnt math... I did go to public school afterall.

Im going to put 3 Lutron switches immediately adjacent to the panel and send wire from there out to my lights. I dont need them at the door as they will be either controlled via smart phone app OR I will have their little remotes all velcro'd right next to my single man door. I may even setup a motion sensor so my exterior lights come on as I approach and my interior lights come on as I enter. Lutron has those as well, but I havent looked into them very deeply.

Not sure if there are multiple entry ways or not but may want to consider and/or need to pull additional wire(s) for 3-way circuits, if any, so you can turn lights on and off from each entry. Agree its just three wires from panel to 1st junction box.

Not running 3 way switches. Lutron Caseta smart switches will be adjacent to the cb panel and controlled via smart phone OR the little remotes they come with, I think called Pico remotes... Im sure not "code legal" but im also not an electrician so theres that also. Im "attempting" to comply with code...to a point.

 

[PCustoms]

I never said I WANTED to pull 9 wires, but if every one of my light circuits(3) require all 3 wires pulled(hot, neutral, ground) thats 9 wires...unless my math doesnt math... I did go to public school afterall.

Your math does not math.

Draw out a quick sketch/floorplan showing where the panel is, where you want your switches and where the 3 banks are

 

[cgrutt]

Not sure how you are routing wires but in general you need three at panel and three at each light fixture. With three switches this could theoretically be accomplished from first junction box with five wires: 3 hots (one from each switch), a neutral and ground. The neutrals and grounds are common and are tied together so you don't necessarily need separate wires for each switched circuit. Of course there's no reason why you couldn't run separate wires but you may not have to depending on how you run your conduit. Hope that makes sense.

 

[rjacobs]

Your math does not math.

Draw out a quick sketch/floorplan showing where the panel is, where you want your switches and where the 3 banks are

how does 3 branches of 3 wires run to each not equal 9 wires... in what world does 3x3 not equal 9????

read again what all I have written...

 

[dave*99]

I never said I WANTED to pull 9 wires, but if every one of my light circuits(3) require all 3 wires pulled(hot, neutral, ground) thats 9 wires...unless my math doesnt math... I did go to public school afterall.

Im going to put 3 Lutron switches immediately adjacent to the panel and send wire from there out to my lights. I dont need them at the door as they will be either controlled via smart phone app OR I will have their little remotes all velcro'd right next to my single man door. I may even setup a motion sensor so my exterior lights come on as I approach and my interior lights come on as I enter. Lutron has those as well, but I havent looked into them very deeply.

Not running 3 way switches. Lutron Caseta smart switches will be adjacent to the cb panel and controlled via smart phone OR the little remotes they come with, I think called Pico remotes... Im sure not "code legal" but im also not an electrician so theres that also. Im "attempting" to comply with code...to a point.

So you have 13 lights and plan to run one conduit to and from a triple gang switch box then daisy chained from light to light to light?
Or something close to that?
If that is the case, you only need to carry one neutral and one ground wire from the panel through the triple gang switch box and to and through each light fixture.

 

[rjacobs]

Not sure how you are routing wires but in general you need three at panel and three at each light fixture. With three switches this could theoretically be accomplished from first junction box with five wires: 3 hots (one from each switch), a neutral and ground. The neutrals and grounds are common and are tied together so you don't necessarily need separate wires for each switched circuit. Of course there's no reason why you couldn't run separate wires but you may not have to depending on how you run your conduit. Hope that makes sense.

THATS WHAT I AM GETTING AT and was asking "is that legal to do"... I believe the consensus is YES...

 

[rjacobs]

So you have 13 lights and plan to run one conduit to and from a triple gang switch box then daisy chained from light to light to light?
Or something close to that?
If that is the case, you only need to carry one neutral and one ground wire from the panel through the triple gang switch box and to and through each light fixture.

yes, I thought I was fairly clear in my question in my OP... is sharing a neutral and ground between 3 branches on the same circuit legal....

 

[PCustoms]

how does 3 branches of 3 wires run to each not equal 9 wires... in what world does 3x3 not equal 9????

read again what all I have written...

Curious if you read post #2 where I explained how to do this, and clearly showed how you only need 2 wires in your conduit, but typically 3 are run.

If you're running 1 conduit out of your switch bank to another junction, then you'd have a max of 5 wires.

Good luck with your project.

 

[cgrutt]

THATS WHAT I AM GETTING AT and was asking "is that legal to do"... I believe the consensus is YES...

I'm not an electrician so take it for what its worth but yes completely legit and how something like this would commonly be wired (provided gauge/type/etc is adequate for overall load). Its functionally equivalent of running separate wires and tying them all back at a common point anyway. Again not electrician so best to confirm with your inspector.

 

[rjacobs]

Curious if you read post #2 where I explained how to do this, and clearly showed how you only need 2 wires in your conduit, but typically 3 are run.

If you're running 1 conduit out of your switch bank to another junction, then you'd have a max of 5 wires.

Good luck with your project.

you said "3 wires from panel to box with switches" then "3 wires to each light bank"...

Your second statement of "3 wires to each light bank" to me means every one of my lighting branches needs 3 wires from the switch box i.e. hot, neutral and ground... thats 9 wires total.

If thats not what you meant, thats how I read it.

 

[rjacobs]

I'm not an electrician so take it for what its worth but yes completely legit and how something like this would commonly be wired (provided gauge/type/etc is adequate for overall load). Its functionally equivalent of running separate wires and tying them all back at a common point anyway. Again not electrician so best to confirm with your inspector.

oh none of this is getting inspected LOL...

#12 THHN is rated to 30amps so its all rated plenty high for what I am looking at doing.

 

[dscheidt]

Remember that a neutral is required in each switch box.
Although 1/2 inch conduit is adequate, pulling multiple 12 ga. wires will be easier with 3/4 especially if there are a few bends.

You do not need a neutral in every switch box, even in romex-land. If there is line of sight between boxes controlling the same lights, you only need a neutral in one of them. In conduit, you need no neutral, if the conduit has room for one later. (If there isn’t room, you have to run it, which means you need a bigger conduit.)

 

[Shiftless]

You do not need a neutral in every switch box, even in romex-land. If there is line of sight between boxes controlling the same lights, you only need a neutral in one of them. In conduit, you need no neutral, if the conduit has room for one later. (If there isn’t room, you have to run it, which means you need a bigger conduit.)

That is true.
You can either put them in now or wait until you need them and put them through the conduit later. Later might never come.
My understanding is that with Romex, typically hidden behind walls, that a white wire must be present in the box.
Obviously since the OP’s project won’t be inspected, such requirements are not pertinent. What does matter is if the OP later decides on a more complicated switch that requires a neutral to make it work, that he would be S.O.L.

I‘m not an electrician, but that is my understanding of the latest codes. Some locales might not require the latest requirements.

 

[sparky 1971]

I never said I WANTED to pull 9 wires, but if every one of my light circuits(3) require all 3 wires pulled(hot, neutral, ground) thats 9 wires...unless my math doesnt math... I did go to public school afterall.

I don't care how many circuits are in one conduit, you only need one ground wire that is sized for the largest circuit. If it's metal conduit like EMT, you don't even need the ground since the pipe will do it for you provided all of the fittings are tight. And, I tried to read this thread but in typical GJ fashion, it's gone sideways and the more I read, the more confused I get. I think you are planning on using one breaker (that's one circuit) with three switches in one box right next to the panel, with each switch feeding one row of lights. If this is the case, you only need one neutral that is common to all of the fixtures along with one hot wire from the panel to the switch box, then you will have three separate switch legs going to the lights. If those are all in one conduit, fine; if it's three conduits, that's fine to, you will then splice the neutrals and grounds if you use them in the switch box.

you said "3 wires from panel to box with switches" then "3 wires to each light bank"...

Your second statement of "3 wires to each light bank" to me means every one of my lighting branches needs 3 wires from the switch box i.e. hot, neutral and ground... thats 9 wires total.

If you're going from the panel to the switch box then to the lights with one conduit using one circuit (breaker) and splitting off with junction boxes, you will have four or five wires: Three switch legs, one neutral, and a ground if you choose to use one. The hot wire will stay at the switch box. If you have three separate conduits from the switch box to the fixtures, you will have two or three per conduit: one switch leg, one neutral, and a ground if you use one.

If thats not what you meant, thats how I read it.

 

[wyliesdiesels]

I was under the impression you cant pull romex through EMT its got to be individual THHN. Anyway I already have spools of THHN so thats going in.

only if you use the urban legend code book

NEC only prohibits NM-b (Romex® is a Southwire brand of NM-b) in outdoor conduit and damp locations. NM-b is only permitted indoors in dry locations.

Having said that, NM-b can be a pain to pull in conduit. THWN will be way easier

 

[wyliesdiesels]

Remember that a neutral is required in each switch box.

not when there is a conduit that can allow the adding of a neutral later

 

[wyliesdiesels]

#12 THHN is rated to 30amps so its all rated plenty high for what I am looking at doing.

while its rated for 30a in the 90° column, that is only for derating purposes. you cant breaker #12 @ 30a for general use receptacles and lighting.

 

[theoldwizard1]

Run a "main" conduit (NM-b) from the load center ...

I was under the impression you cant pull romex through EMT its got to be individual THHN. Anyway I already have spools of THHN so thats going in.

poor wording on my part !

I should have said "Run a 'main' conduit OR NM-B from the load center ..."

 

[BurtEggley]

when I read shared neutral I thought of the two to-code-in-1979 circuits in my house that share a neutral. If both breakers aren't turned off when working on either circuit you will get bit if you assume it is dead since they are on different phases, but only with enough to sting. My electrician and the inspector said they allowed that back then.

 

[dave*99]

when I read shared neutral I thought of the two to-code-in-1979 circuits in my house that share a neutral. If both breakers aren't turned off when working on either circuit you will get bit if you assume it is dead since they are on different phases, but only with enough to sting. My electrician and the inspector said they allowed that back then.

Add a handle tie to the two breakers on this multi wire branch circuit and problem's solved.

 

[BurtEggley]

too far apart unless wires extended in panel. I marked both with a warning label that is clear, and there is a warning label in the box. But you have a great idea. If we upgrade the panel someday I will make sure it is dealt with.

 

[sparky 1971]

when I read shared neutral I thought of the two to-code-in-1979 circuits in my house that share a neutral. If both breakers aren't turned off when working on either circuit you will get bit if you assume it is dead since they are on different phases, but only with enough to sting. My electrician and the inspector said they allowed that back then.

If someone doesn't pay attention to the labels and only shuts one breaker off, it could be a little more than a sting. It might be just in my head, but I think it hurts more when getting hit from the neutral. That's why handle ties or two pole breakers are now required. And If something goes awry with the neutral of any of those circuits some things are going to see 240 volt and may not like it but there's not much can be done about that.

 

[dscheidt]

too far apart unless wires extended in panel. I marked both with a warning label that is clear, and there is a warning label in the box. But you have a great idea. If we upgrade the panel someday I will make sure it is dealt with.

You can extend wires in a panel.

My brother used to have a mwbc where the two breakers were not in the same panel. That’ll get someone.