Neutral Question

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JohnME

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Went to a job today that had 2 sub panels feeding various lights and receps. There was a 3 wire going to a junction box, I followed it back to the panel, where it split at another junction box. The Neutral is from one sub panel and the 2 20amp circuits are coming from the other. Both sub panels feed back to another panel, at the entrance of the service where both sub panels' Neutrals are tied into the Neutral bus bar.

What kind of problems will this lead to? Obviously someone wasnt paying attention or forgot to pull an extra Neutral to the first j box. This was existing and if I am going to pull the owners attention to it I would rather have some concrete facts about what will happen if it is left alone then to just grasp for straws. Thanks.
 
This could pose an electrocution hazard if someone were to be working on the subpanel that had the neutral ran to it if they were to remove the panel neutral.This was the reason for requiring handle tie breakers on MWB circuits ,a person could turn off power in the sub panel but the neutral would be carrying current from the other panel.
 
I know this!

I know this!

I want U to know I jumped all over this back in forth, just thought provoking, "I know this is wrong, its the one I got burned on the weekend."
(here not in real time)

210.4
...
"all conductors of a multiwire branch circuit shall orginate from the same panelboard or similiar disturbution equipment." ...
 
As Rewire mentions, this is definitely a hazard. With the neutral going to the wrong panel, and if someone turned off the feed to that panel, they would assume everything in the panel is dead. But if you removed that mis-wired neutral from the neutral bus, it could actually be energized.

On that note, if the line side of the feeder neutral was lifted off its bus, the feeder neutral could be energized too.

Now, I hope everyone realizes that the shock hazard of an open neutral has absolutely nothing to do with the amount of amp load connected to that neutral. It could be a 5 watt incandescent bulb, or a 50 amp load, the shock hazard is essentially the same.
 
You guys are great, thank you very much.

When your hooked to the Neutral end of a motor it hurts a lot, more so then a light bulb? Dont know, just know its not much fun.
 
ok, one neutral two hots different panels. Lots of issues. If the other sub panel was eliminated the two circuits would stop working. If the two hots are on the same phase then the neutral could burn up. If there was a problem with the neutral being loose or broken there would be no causality between the circuits and the neutral. Thats a fancy way of saying it would be a bear to find and fix. 2008 says ALL 20 and 15 amp circuits are to be Arc fault protected. How you do that with a neutral going to different panels isn't possible.
Sounds like an opportunity to sell 2 new breakers and 2 new circuits! Just tell the home owner its a fire hazard and you corrected it. How much are his house, kids, family worth? You know its wrong, luckily he hired you and you found it. Thats cause your one crackerjack electrician. Just fix it.
 
crossman said:
It hurts the same amount.
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Perception is reality.:smile: Maybe I made a better connection with my fingers because it was a neutral and I thought the line was dead but getting between a neutral was the worst hurt I remember.
 
Okay, I'll grant you that, but according to the laws of physics, getting in series with the phase conductor is just as bad as getting in series with the neutral conductor. And again, the actual connected load has little to do with the severity of the shock.
 
crossman said:
Okay, I'll grant you that, but according to the laws of physics, getting in series with the phase conductor is just as bad as getting in series with the neutral conductor. And again, the actual connected load has little to do with the severity of the shock.
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But why does it seem to hurt more? :rolleyes:
 
e57 said:
But why does it seem to hurt more? :rolleyes:
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Maybe, due to carelessness around a neutral, we don't "get between the hots". For a hot zap, we usually get a hot-to-ground shock. Maybe the ground path makes the "hot shock" less painful. Looking at the paths and ignoring the conductor:

The times I've been zapped by the hot, it was from the source ungrounded line (UL), through me and through the ground/contact impedance of whatever I was grounded against and back to the source grounded line (GL). So the path was:

UL-contact1_imp-ME-contact2_imp-gnd_imp-GL.

For the neutral, the path would be ungrounded line to load to me and contact impedance to the source grounded line. This path would be:

UL-load_imp-contact1_imp-ME-contact2_imp-GL

I guess one difference is that, because of carelessness, the contact1 & contact2 impedances are much less for the neutral case (you have a good contact with the wires). In the hot to ground case, your contact with ground may not be so good and you probably would not touch a hot as hard because of being cautious.
 
I agree with your comments.

However, the blanket statement "getting in series with the neutral is the worst you will ever get shocked" is simply a blanket statement unsupported by fact. The reason this statement is made is because some people think that the entire load current is passing through the body.

For example, take a 120V circuit with 14 amps of load current. Break the neutral and get in series with it. Some folks will assume that the load current of 14 amps flows through the body parts in series with the neutral. But they are ignoring ohm's law of the newly created series circuit.
 
Gods a calling!

Gods a calling!

When I get shocked I think of it as Gods way of saying I'm not being careful enough and he is a call in me HOME! Can I get an AMEN!

What are you doing getting shocked anyway? Aren't you a paid professional? Haven't you forgotten those little professional secrets like DICONNECT and UN energized? Remember, it cooks you all the way from source to exit, like a piece of seared medium rare steak. Off is good. It might inconvenience someone but it also impresses them about the importance of our paid profession. So either become an 11 o'clock news item to impress everyone how dangerous our jobs are; or an example of a paid professional electrician. AMEN!
 
crossman said:
Some folks will assume that the load current of 14 amps flows through the body parts in series with the neutral. But they are ignoring ohm's law of the newly created series circuit.
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Those are the people who also believe a wiggy will expolde if you measure across an open fuse in a high-current circuit.
 
LarryFine said:
Those are the people who also believe a wiggy will expolde if you measure across an open fuse in a high-current circuit.
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I saw that! I went to check across a 100 amp fuse to see if it was blown, and the guy that was with me took off running, yelling "don't do that!" I asked why, he said "because all 100 amps will go through your wiggie and it will blow up". I told him he was wrong. He said "no really, I saw it happen once, and the guy got hurt really bad". I sat him down and gave him some lessons in ohm's law and series circuits.
 
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