Combined Neutrals and the NEC

[rwilsond]

Here's an oddity I came across. An electrician was called to a house, because of lights flickering. He came to believe there was an open in the neutral of a 2-wire branch circuit. But he was unable to locate and correct the open. So, he jumpered the neutral to the neutral of another 2-wire branch circuit, in an existing outlet box.

Which sections of the NEC did he violate?

 

[ptonsparky]

310.4 for one.

 

[480sparky]

310.4 for one.

No, he just used the noodle from another circuit. The original noodle won't carry any current if it's open, so there's no paralleling.

But I'd vote for 300.3(B) and 210.21(B).

 

[rwilsond]

No, he just used the noodle from another circuit. The original noodle won't carry any current if it's open, so there's no paralleling.

But I'd vote for 300.3(B) and 210.21(B).

Thanks for that. But how could 210.21(B) apply? I'm looking at the 2005 & 2008 NEC's, and see that it's about receptacle ratings.

And, just to clarify, all parts of both neutrals will carry current. It was the broken piece that he connected to another neutral. So, to kill power in that 2-wire romex, one would now need to switch off two CB's.

 

[dbuckley]

An uninformer individual did that a my current house, and when I changed a wall light I got a belt, 'cos although I'd turned off the breakers for the downstairs lighting, this retard had jumpered a neutral into the garage lights on the opposite sides of the wall the wall lights were on.

So I dont care what NEC sections it violates; its just plain dangerous to your fellow electrician.

 

[ptonsparky]

480,
It's open and not parallel until it decides to flicker back together again, but your right 300.3(B) is the better answer.

...and I was gonna look that one up but I got sidetracked with actual work.

 

[erickench]

Well if neutral is shared then would'nt it be considered a multiwire circuit?

 

[480sparky]

Thanks for that. But how could 210.21(B) apply? I'm looking at the 2005 & 2008 NEC's, and see that it's about receptacle ratings.

And, just to clarify, all parts of both neutrals will carry current. It was the broken piece that he connected to another neutral. So, to kill power in that 2-wire romex, one would now need to switch off two CB's.

My bad. 210.20(B).

 

[NolaTigaBait]

My bad. 210.20(B).

Somebody is getting senile.....:grin:

 

[480sparky]

Somebody is getting senile.....:grin:

Eh?!?! What'd you say, sonny? Speak up! Dang punk kids!

Get off my lawn!

 

[erickench]

Well if it's a multiwire branch circuit then you would need a simultaneous disconnect as stated in 210.4(B). Also, make sure the two ungrounded conductors are not on the same phase otherwise you're gonna have a real problem.

 

[rwilsond]

Well if it's a multiwire branch circuit then you would need a simultaneous disconnect as stated in 210.4(B). Also, make sure the two ungrounded conductors are not on the same phase otherwise you're gonna have a real problem.

He tells me that the circuits are on separate phases.

Yes, I am also thinking he created a multiwire circuit (albeit, improperly so). So far, I'm thinking the following sections of the 2008 NEC are of concern: 210.4(B), 210.4(D), 300.3(B), and possibly 240.4 (until I can verify that the circuits are on separate phases).

Thanks to all that assisted.

 

[paul]

Was this a permanent fix, or just a troubleshooting technique?

 

[rwilsond]

It started out as troubleshooting. Then became a "temporary" fix, as it was getting late in the day. But what is an acceptable duration of such a temporary fix, if it doesn't comply with code from the get-go? I just want to be on firm ground (with specific NEC section references) when I state that it should be corrected ASAP.

 

[JdoubleU]

I don't have the 2008 code in front of me, but I would say 210.4. The sharing of the neutral would be fine but the 2 circuits would to have shut off together.

 

[macmikeman]

So this leads me to wonder, what if it was two small loads 3.5 amps each for instance, on a three wire circuit that has a common grounded circuit conductor and they are on the same leg. Would a two pole breaker be required since technically this is not a multiwire branch circuit? (For 2008) Would the above installation be a code violation even if a two pole breaker was used in the first place? I would have to say that it is a bad idea to do something like this, but code compliant?

 

[rwilsond]

So this leads me to wonder, what if it was two small loads 3.5 amps each for instance, on a three wire circuit that has a common grounded circuit conductor and they are on the same leg. Would a two pole breaker be required since technically this is not a multiwire branch circuit? (For 2008) Would the above installation be a code violation even if a two pole breaker was used in the first place? I would have to say that it is a bad idea to do something like this, but code compliant?

But "a three wire circuit" IS technically a multi-wire circuit. A 2-p CB would suffice, but so would two 1-p CB's that have a common tie-bar. And, if all loads are single-phase, then 210.15(B)(1) of the 2008 NEC allows two 1-p CB's w/o a common handle-tie (like you, I much prefer the common handle-tie).

 

[macmikeman]

But "a three wire circuit" IS technically a multi-wire circuit. A 2-p CB would suffice, but so would two 1-p CB's that have a common tie-bar. And, if all loads are single-phase, then 210.15(B)(1) of the 2008 NEC allows two 1-p CB's w/o a common handle-tie (like you, I much prefer the common handle-tie).

I think they have to be on opposite legs to qualify for "multiwire" branch circuit. I'm going to have to read it out of the book to be sure about that but not tonight, in the morning.... yawn.