busting neutrals

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billdozier

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Hey guys troubleshooting a bad deadend 3way 2day. the rough crew had tied the wrong white in with the hots and tied the common white to the neutrals. So I busted the neutrals apart with the breaker on. My partner said that I could have fried the microwave and fan if they had been on the same ckt. Ive heard this before but do not understand the theory behind it. Would love some confirmation on this and an explanation as to why this would happen thanks the dozier
 
This doesn't sound like a MWBC to me. It sounds like the guy said, "If the load was on the same circuit as a short circuit, the load could get damaged."

I have a hard time picturing that, myself. I'm not saying it's not true, but I have a hard time visualizing that. I would think the load would see an undervoltage during the event.
 
If it was a single circuit spliced at the switch location this could not happen. If it was a mwbc aka as more than 1 hot with a shared neutral and the neutral was broken and put under a load it certainly could damage equipment
 
to give you guys some more information on this exact application. It was a standered 14-2 15 a ckt. Carried lights in the kitchen fan in living rm backporch light basic lighting ckt. I called him on his comment due to this especially the microwave since it was a seperate ckt didnt see how it could be affected by me busting neutrals wanted to make sure I was correct in my view point. I think weve all busted lighting ckt neutrals apart at one point in time or another. also looking at the link on mwbcs it seems like they may quickly be becoming a thing of the past? recently did a small storefront/warehouse job singlephased where we had receps on ckts 1 and 3 i pulled two hots and one grounded wire for these plugs. How would you guys have handled the situation? I dont have a 2008 nec at this time as were not inspected on the 08 however it seems there is a major change in grouping of mwbcs and grounded conductors could someone please post the code statement or recomend a site to view this code change thanks
 
Bill, if you bust the neutral on a live multi wire branch circuit you can indeed fry things that are down line.

Now put that aside for minute, it is NEVER a good idea to make circuit changes on a live circuit.

We should not be working live anyway, but changing connections on a live circuit is a real bad plan. What would happen if you new changes where wrong, it blows up in your face.
 
Bill,
Like Bob said, it is a bad practice to pull apart or handle neutrals on live circuits.
I hope your working partner just didn't know what was on the circuit when he made his comment. Better keep an eye on him.
I was on a tall ladder in an Office Depot one day many years ago. I opened a junction box and out fell a red wirenut. Somebody didn't tighten it during the initial installation. Smoked about five or six computers that were on display.
I was fortunate that nobody said a word about it. They had then all changed within an hour. That was back when desktops were the price of a used car.

Otherwise, in your later post, I think your use of the MWBC on the installation was good and proper.
 
jrannis said:
I was on a tall ladder in an Office Depot one day many years ago. I opened a junction box and out fell a red wirenut. Somebody didn't tighten it during the initial installation. Smoked about five or six computers that were on display.
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LOL :D

I was on a lift in a Comp USA, opened a 4" square that I should not have, it had way to many KOs used I should have known better. But I pull the cover off anyway and out pops a red wire nut and the neutral splice comes apart .... you know the kind of splice that people have added to a few times without doing it right.

Well right away I hear a buzz .... not good :D ....... look around see smoke rising from a Apple display aisle.

I got the splice back together go down and check out the aisle, I got lucky the smoke came from surge suppressor plug strips and once I replaced those everything fired up.
One of the employees came by and asked if the 'clutch' in my lift was OK because he could smell a clutch burning up front. I said no clutch but that the electric motor was hot. ;)
 
iwire said:
LOL :D

I was on a lift in a Comp USA, opened a 4" square that I should not have, it had way to many KOs used I should have known better. But I pull the cover off anyway and out pops a red wire nut and the neutral splice comes apart .... you know the kind of splice that people have added to a few times without doing it right.

Well right away I hear a buzz .... not good :D ....... look around see smoke rising from a Apple display aisle.

I got the splice back together go down and check out the aisle, I got lucky the smoke came from surge suppressor plug strips and once I replaced those everything fired up.
One of the employees came by and asked if the 'clutch' in my lift was OK because he could smell a clutch burning up front. I said no clutch but that the electric motor was hot. ;)
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Ha! Small world.
If for some reason I have to jump on one of those bundled neutrals, I tape all of the existing conductors together before I remove the wirenut. Its not 100% I know, but I havent had a problem yet:roll:
 
Opening a neutral on a 2 wire circuit will not affect downstream equipment. How ever after opening the splice you can receive a severe shock from the neutral conductor. Not as severe as the shock you'll receive from a hot leg but a potentially fatal shock nevertheless.
 
Kdawg67 said:
If the neutrals are tied together (say 2 14-2's in a box) and you open the neutrals, wouldn't you lose your neutral downstream? I would think that would affect it. (i.e. no more hot to neutral voltage):confused:
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By affect I meant possibly blowing up downstream equipment. That's a real possibility when opening a shared neutral from a MWBC. On a 2-wire circuit the equipment would just shut off. IMO what's more important is the shock potential from the now open neutral.
 
Kdawg67 said:
If the neutrals are tied together (say 2 14-2's in a box) and you open the neutrals, wouldn't you lose your neutral downstream? I would think that would affect it. (i.e. no more hot to neutral voltage):confused:
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If you were to meter it it would (or should) read 0 volts Line-to-Neutral. The 'downstream' neutral, however, will read line voltage to ground if you were to meter it (assuming your meter could handle the amperage impressed through it by the circuit).
 
Oh yes I can still hear the sound of the red wire nut hit the floor
and the smell of smoke. I too have fallen victim to,
"The Parallel Circuit now in Series Nightmare."
 
infinity said:
Opening a neutral on a 2 wire circuit will not affect downstream equipment. How ever after opening the splice you can receive a severe shock from the neutral conductor. Not as severe as the shock you'll receive from a hot leg but a potentially fatal shock nevertheless.
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From my experiance, grounding yourself out to a hot wire will push you off of it, but completing a circuit either through a hot or neutral will hold onto you.
 
aftershock said:
From my experiance, grounding yourself out to a hot wire will push you off of it, but completing a circuit either through a hot or neutral will hold onto you.
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Get between a hot and ground, and the amperage is detemined solely by your body's resistance.

Get between an open neutral and ground, and you get hit with the amperage the circuit is drawing.
 
infinity said:
Opening a neutral on a 2 wire circuit will not affect downstream equipment. How ever after opening the splice you can receive a severe shock from the neutral conductor. Not as severe as the shock you'll receive from a hot leg but a potentially fatal shock nevertheless.
Click to expand...
can't the shock received form the neutral in this case be worse than the hot leg itself?
 
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