# Sharing a neutral



## HackWork (Oct 2, 2009)

Hmmmmm, I don't know. 30A makes it seem weird, but if someone ran a #12-3 and then used a 20A and 15A breaker with a handletie, that would be allowed, right? I don't know of any code requiring them to be the same size. Maybe there is...



> I get that worse case scenario the neutral will carry 10 amps at the most because the 20/30 circuit breakers but just don’t seem right.


 In your situation the neutral will carry 30A at the most. But it is sized for that, so it's ok.


----------



## Helmut (May 7, 2014)

The 30 circuit was prob already there, and someone came along and pulled one 12 ga wire, tapped off the existing neutral, put in a 20A breaker and called it a day.


----------



## Surge03 (Sep 23, 2012)

Would an inspector be ok with this in a new install? For example would I be aloud to install one 15, one 20 and one 30 and pull a #10 neutral LMAO. Save money by pulling dedicated neutrals to each circuit.


----------



## HackWork (Oct 2, 2009)

Surge03 said:


> Would an inspector be ok with this in a new install? For example would I be aloud to install one 15, one 20 and one 30 and pull a #10 neutral LMAO. Save money by pulling dedicated neutrals to each circuit.


Do you know of a code article prohibiting it?


----------



## Surge03 (Sep 23, 2012)

No but never seen it done. So the issue I have here is the person ran the #10 neutral in series thru the 20 receptacle than fed the 30 amp appliance. That being said, the other outlet was just feeding a computer drawing milliamps at the most. I’m assuming the neutral was carrying 25 amps continuously thru that 20 amp receptacle. Yes, I could parallel the neutral and be done with it but some idiot behind me can put it back in series.


----------



## Wirenuting (Sep 12, 2010)

I’ve seen to done a few times and never had a problem.
Always sized to the largest breaker. 
But never thru a receptacle, always pigtailed them off.


----------



## CoolWill (Jan 5, 2019)

Surge03 said:


> No but never seen it done. So the issue I have here is the person ran the #10 neutral in series thru the 20 receptacle than fed the 30 amp appliance. That being said, the other outlet was just feeding a computer drawing milliamps at the most. I’m assuming the neutral was carrying 25 amps continuously thru that 20 amp receptacle. Yes, I could parallel the neutral and be done with it but some idiot behind me can put it back in series.


Some idiot could also come along and pull out your new neutral and replace it with phone wire. Do things the best way they need right now and don't worry about what someone might do in 50 years.


----------



## joebanana (Dec 21, 2010)

Your terminology needs work. Neutrals don't "feed" anything, they're a return. If you wire a recep. in series, it won't work, unless some load is plugged into it that the rest of the circuit gets fed through.
Being a MWBC the breaker handles must be tied. I've never seen a 2 pole 20/30. If both breakers are on the same "phase", the #10 neuch could be overloaded.


----------



## CoolWill (Jan 5, 2019)

joebanana said:


> Your terminology needs work. Neutrals don't "feed" anything, they're a return.


How are you going to tell him to work on his terminology and then say that the neutral is a "return"?


----------



## HertzHound (Jan 22, 2019)

The neutral wire should always pigtailed where two circuits split. It should never rely on the device to make the connection. Doing that wrong is probably the main reason that they make us use handle ties on multiwire branch circuits. 



> 300.13 Mechanical and Electrical Continuity — Conductors.
> 
> (B)Device Removal.
> In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity.


----------



## dronai (Apr 11, 2011)

joebanana said:


> Your terminology needs work. Neutrals don't "feed" anything, they're a return. If you wire a recep. in series, it won't work, unless some load is plugged into it that the rest of the circuit gets fed through.
> Being a MWBC the breaker handles must be tied. I've never seen a 2 pole 20/30. If both breakers are on the same "phase", the #10 neuch could be overloaded.


Yo Banana, it's alternating current, the neutral is not only return


----------



## micromind (Aug 11, 2007)

I've run a 50 amp 125/250 volt recept using 2 #6s and a #6 neutral plus a basic 20 amp 120 volt recept using the same neutral from a 3Ø panel.

Seems odd of course but there's no hazard of code violation.


----------



## sparkiez (Aug 1, 2015)

The code defines how a multi-wire branch circuit is supposed to be installed. This is not an example of a proper install. The code also defines when and how you can tap off of a larger circuit with smaller wire and additional/supplementary circuit protection. This is not an example.


No, an inspector would not pass this.


----------



## joebanana (Dec 21, 2010)

CoolWill said:


> How are you going to tell him to work on his terminology and then say that the neutral is a "return"?


Well, it is. If it's not a source, it's a sink.


----------



## joebanana (Dec 21, 2010)

dronai said:


> Yo Banana, it's alternating current, the neutral is not only return


It's what the current returns to the source on, same with ground.


----------



## splatz (May 23, 2015)

sparkiez said:


> The code defines how a multi-wire branch circuit is supposed to be installed.


Does it? Other than the restriction in 300.13 that @HertzHound posted, and handle ties, it doesn't seem to have any specific rules about multiwire branch circuits. 

I wouldn't be surprised if it wasn't passed, but that doesn't mean the inspector is right.


----------



## macmikeman (Jan 23, 2007)

joebanana said:


> It's what the current returns to the source on, same with ground.


There won't be any current if one of the wires ain't there. Current moves in both directions - it alternates. Alternating current. 60 hz in USA. Open the neutral, hold one end stripped in each hand. You will get shocked 60 times each direction every second you stand there holding it.......


----------



## CoolWill (Jan 5, 2019)

joebanana said:


> Well, it is. If it's not a source, it's a sink.





joebanana said:


> It's what the current returns to the source on..


Half the time, yes. The other half the time it is the source.



> same with ground.


During a ground fault, as much current comes from the grounding conductor as goes into it.


----------



## HackWork (Oct 2, 2009)

sparkiez said:


> The code defines how a multi-wire branch circuit is supposed to be installed. This is not an example of a proper install. The code also defines when and how you can tap off of a larger circuit with smaller wire and additional/supplementary circuit protection. This is not an example.
> 
> 
> No, an inspector would not pass this.


With all due respect, if you are going to speak of code, you really should cite the code that prohibits it. Until then, it is completely allowable. By what the OP described, the only thing that code prohibits is using the device instead of making up a pigtail splice.

I will also point out that the situation that the OP described does not have a "smaller wire tapping off of a larger circuit".


----------



## sparkiez (Aug 1, 2015)

splatz said:


> Does it? Other than the restriction in 300.13 that @*HertzHound* posted, and handle ties, it doesn't seem to have any specific rules about multiwire branch circuits.
> 
> I wouldn't be surprised if it wasn't passed, but that doesn't mean the inspector is right.



I'm studying for my last two finals right now, but when they are done I'll be happy to provide the relevant code references. The code states that they must use a handle tie, that any neutrals must be tied together by means other than a device connections, that each circuit on the same line of the supply must have its own neutral and it specified in other ways how circuits are allowed to be branched out. For instance, you aren't allowed to go from #10 on a 30A breaker to #12 without fault extra protection. You could then get 30A on the #12 wire without the circuit opening and burn up the wire.

There is also a section of the code that states that each circuit must be separate and complete back to the panel. You can't just willy-nilly pull nuetrals between circuits like they used to do with K&T. It is specifically addressed in Wiring methods and materials.


Give me a couple days and I'll get the exact references to back up my statements, though.


----------



## CoolWill (Jan 5, 2019)

sparkiez said:


> I'm studying for my last two finals right now, but when they are done I'll be happy to provide the relevant code references. The code states that they must use a handle tie, that any neutrals must be tied together by means other than a device connections, that each circuit on the same line of the supply must have its own neutral and it specified in other ways how circuits are allowed to be branched out. For instance, you aren't allowed to go from #10 on a 30A breaker to #12 without fault extra protection. You could then get 30A on the #12 wire without the circuit opening and burn up the wire.
> 
> There is also a section of the code that states that each circuit must be separate and complete back to the panel. You can't just willy-nilly pull nuetrals between circuits like they used to do with K&T. It is specifically addressed in Wiring methods and materials.
> 
> ...



None of that applies to the OP except where the device completes the neutral.


----------



## sparkiez (Aug 1, 2015)

CoolWill said:


> None of that applies to the OP except where the device completes the neutral.



It absolutely does.


To wit:
Tapping off of a branch circuit in excess of wire ampacity
Potentially improperly installing a multi-wire branch circuit, of which this install is considered
Wiring methods and materials requirement that each circuit have a clean, unshared neutral back to source except where exceptions are made for MWBC


As I said, I'll provide the code references. This isn't wrong because it says in the code it is wrong. It is wrong because of several different sections of the code that specific installations shall occur in a way that the OP's setup violates.


----------



## HackWork (Oct 2, 2009)

sparkiez said:


> It absolutely does.
> 
> 
> To wit:
> ...


You are misapplying the code.

And you are completely confused on the tapping thing.


----------



## CoolWill (Jan 5, 2019)

sparkiez said:


> It absolutely does.
> 
> 
> To wit:
> Tapping off of a branch circuit in excess of wire ampacity


The OP doesn't discuss this. One breaker is 30, one is 20. The neutral is #10, which is plenty for either circuit.



> Potentially improperly installing a multi-wire branch circuit, of which this install is considered


Which is the part about using the device to complete the neutral path.



> Wiring methods and materials requirement that each circuit have a clean, unshared neutral back to source except where exceptions are made for MWBC


Which is what we're talking about, an MWBC.




> As I said, I'll provide the code references. This isn't wrong because it says in the code it is wrong. It is wrong because of several different sections of the code that specific installations shall occur in a way that the OP's setup violates.


The only violation is using the device to complete the neutral. If it was installed prior to 2008, the handle tie requirement wouldn't apply. No code rule exists now or in the past requiring the breakers of an MWBC be the same size.


----------



## HackWork (Oct 2, 2009)

CoolWill said:


> The OP doesn't discuss this. One breaker is 30, one is 20. The neutral is #10, which is plenty for either circuit.
> 
> 
> 
> ...


Oh no you didn't. Wait until he comes back next month with the code articles to put you in your place!


----------



## CoolWill (Jan 5, 2019)

HackWork said:


> Oh no you didn't. Wait until he comes back next month with the code articles to put you in your place!


:surprise:Now I'm concerned. What will happen?:sad:


----------



## HackWork (Oct 2, 2009)

CoolWill said:


> :surprise:Now I'm concerned. What will happen?:sad:


I'm not sure, but I do remember that he one time proved that global warming is real by linking to an article by Bill Nye, the actor with no education in science. So I assume the substantiation he provides here will be just as concrete :biggrin:


----------



## CoolWill (Jan 5, 2019)

HackWork said:


> I'm not sure, but I do remember that he one time proved that global warming is real by linking to an article by Bill Nye, the actor with no education in science. So I assume the substantiation he provides here will be just as concrete :biggrin:


I'm just glad Carl Sagan died before he had to play the same tune as Bill Nye in shame.


----------



## dronai (Apr 11, 2011)

joebanana said:


> Well, it is. If it's not a source, it's a sink.


You're thinking DC


----------



## sparkiez (Aug 1, 2015)

CoolWill said:


> The OP doesn't discuss this. One breaker is 30, one is 20. The neutral is #10, which is plenty for either circuit.



Jesus man, you have the potential here for a 20A breaker and a 30A breaker to be loaded on a #10 neutral on the same phase. The OP doesn't specify if the 20A and 30A are on the same line. If they were 220V equipment with the neutral just being for control or some such, perhaps not such a big deal in reality.


If it is single phase equipment carrying that load, then it needs to be specified which line they are on. Unless specified, I will assume they aren't.


----------



## HackWork (Oct 2, 2009)

sparkiez said:


> Jesus man, you have the potential here for a 20A breaker and a 30A breaker to be loaded on a #10 neutral on the same phase. The OP doesn't specify if the 20A and 30A are on the same line. If they were 220V equipment with the neutral just being for control or some such, perhaps not such a big deal in reality.
> 
> 
> If it is single phase equipment carrying that load, then it needs to be specified which line they are on. Unless specified, I will assume they aren't.


This is a really, really silly thing for you to assume.

Using your logic, every multi wire branch circuit installed before the 2008 code requirement of using a handle tie could be overloaded by having the individual breakers on the same phase or leg.

It’s a completely unreasonable thing to just assume out of thin air.


----------



## CoolWill (Jan 5, 2019)

sparkiez said:


> Jesus man, you have the potential here for a 20A breaker and a 30A breaker to be loaded on a #10 neutral on the same phase. The OP doesn't specify if the 20A and 30A are on the same line. If they were 220V equipment with the neutral just being for control or some such, perhaps not such a big deal in reality.
> 
> 
> If it is single phase equipment carrying that load, then it needs to be specified which line they are on. Unless specified, I will assume they aren't.


You've always had that potential, it doesn't matter if the breakers are the same size or not. The OP even said



> I thought the neutral could only be shared if the breakers are the same size on a single phase or three phase.


This implies they are on opposite phases. I'm not arguing that this is a desirable situation. I'm just saying that you won't find a code that forbids it.


----------



## splatz (May 23, 2015)

CoolWill said:


> You've always had that potential, it doesn't matter if the breakers are the same size or not ... This implies they are on opposite phases. I'm not arguing that this is a desirable situation. I'm just saying that you won't find a code that forbids it.


I couldn't find a code that prohibits it. I thought it was maybe a loophole, a goofy thing they never thought to make a rule against, and if it got someone's attention, there would be a rue. But I am having trouble seeing an actual hazard here if the neutral conductor is sized for the largest breaker.


----------



## gpop (May 14, 2018)

If the breaker are on different phases then the Neutral should have been big enough so it shouldn't have melted. BUT it did.

That brings us to ...."The neutral melted underground due to loose connection"

Im guessing this is a underground j-box as where else would the loose connection be.
(op is a maintenance sparky)

So what im reading is a neutral burnt up due to a loose wire nut.

I personally would run a 2 neutrals if it avoided having to wirenut in a underground J-box. Its not required but 
I hate underground splices, its a easy thing to do, I didn't buy the wire.....come to think of it i would re-pull all the wires in the conduit just to make my life easier.


----------



## joebanana (Dec 21, 2010)

macmikeman said:


> There won't be any current if one of the wires ain't there. Current moves in both directions - it alternates. Alternating current. 60 hz in USA. Open the neutral, hold one end stripped in each hand. You will get shocked 60 times each direction every second you stand there holding it.......


But the current isn't coming from the grounded end, it's going to it. It comes from the source, goes through the load, and returns to the source. The neutral doesn't "feed" anything. 60 times a second. If you hold the neutral, and not the source, you won't get shocked. Unless it has a load on it, and you're grounded. Oh.......never mind.


----------



## gpop (May 14, 2018)

Someone years ago explained to me that the generator pushed and pulled the electrons. Its like blowing and sucking on a straw.

240 is 2 straws with one blowing and the other one sucking at the same time.


----------



## stiffneck (Nov 8, 2015)

gpop said:


> If the breaker are on different phases then the Neutral should have been big enough so it shouldn't have melted. BUT it did.
> 
> That brings us to ...."The neutral melted underground due to loose connection"
> 
> ...


 Ah yes those ma-ma-ma-maintenance guys. I can't tell you how many times that wire refuse to pull out. Once you get going, there's no stopping and next thing you know the jack-hammer has to be brought out :furious:
I hate under ground splices too, especially poorly maintained street lights.


----------

