Inadvertent ground fault during construction?

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Inadvertent ground fault during construction?

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e57

e57

Senior Member
Location
San Francisco, CA
Just wondering about the practices of some people... I come across this often, and I am having trouble understanding why these people do not see a particular hazard...

The scenario:
A building is roughed in, for whatever reason they want to test the install, power it to ward off/kill sheetrockers, or provide temp power. They will tape off/insulate all the phase (ungrounded) conductors, but not tape off the neutral (grounded) conductors.
 
I've never taped/capped the neutrals because on my jobs they are spliced as soon as they are installed so that nobody can put themselves in series with the load, and any pigtails are tucked nicely into plastic boxes or capped in metal boxes. Still I won't energize a circuit unless it's complete in itself to the point of any load attached to it. If it is temporary, it is still complete, and can be modified later to suit another purpose.
 
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In the areas around Phoenix,Az. The feeders are locked out by the EI until the devices or

equipment downstream are connected. I don't know if residential is the same or not.
 
In the areas around Phoenix,Az. The feeders are locked out by the EI until the devices or equipment downstream are connected. I don't know if residential is the same or not.
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Locked out by EI?? I've never seen an inspector do any kind of "work"



We do a lot of resi remodel and often have energized wiring capped and tucked into boxes until trim. I never nut off the neutrals. If I should (excluding AFCI/GFCI circuits) please enlighten me.
 
220/221 said:
We do a lot of resi remodel and often have energized wiring capped and tucked into boxes until trim. I never nut off the neutrals. If I should (excluding AFCI/GFCI circuits) please enlighten me.
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My current job with a new employer also does not cap off the neutrals - which I found odd. Especially since they planned to energize ALL of it.

The result - due to several ground faults, was ~10A of sparking and current on the plumbing while someone was working near the temp main panel. This was due to a parallel path for neutral current as one of the faults was a neutral to EGC in a metal box to metal framing which also contained plumbing.

In the past - I had a job where someone had done the same - not taped off a neutral, and I showed up to the job and saw puffs of smoke out of a box... Turned out the #12 neutral was carrying 50% unbalanced current of several 3 phase panels, (~50A....) then back out on the EGC - then back to the main...

A common practice is to install GFCI recept's on the installed wiring and just wirenut the switches for lighting. However, the ground fault often happens prior to the device in temp situations. I'm wondering if there should be a code for such things that clearly spells out where the protection should be?

In the past in other companies we would put a 50A GFCI breaker in for spider boxes, and then feed the wiring temp'ed from that. If someone did not cap off a neutral it would trip. For that matter if something happened where the wiring was disturbed by rockers it would also trip - even if not energized. Essentially shutting down at least a portion of the job. A nuisance at best, but safe IMO.

Anyway - I too treat neutrals as hots - sometimes the worst shock you can get is from one... ;)
 
Capping the hots and not capping the neutrals strikes me as being either lazy or cheap. Wire nuts and tape aren't expensive. That said, I'd rather have a device on the end than some wire nuts, but ya can't always get whacha want.
 
i selected "i don't energize incomplete wiring."

I don't energize unless all the devices are in; no point in doing so that I can see. If another tradesman sees a device box with no device, they usually automatically assume those conductors are dead. A lot of guys around here like to use the electrical system as the antenna for their stereo while working. And no, I don't find a lot of humor in purposely shocking someone. not that I like being the babysitter, but it is a huge liability to energize an incomplete circuit unless you're going to blank every opening.
 
I voted no but I have to clarify. If I energize something, it's not to test it but to provide temp power, in which case I don't wire past the receptacle I'm hooking up for temp power. For lighting and smoke detector boxes I always twist and wirenut all the leads during rough-in, so for them it would be a "yes" answer. I almost always cap off both the hot and neutral of receptacle feeds (home runs), especially when I know there's going to be a GFI there.

If I were still working with metal boxes exclusively or when I do commercial, my answer would be different.
 
PetrosA said:
I voted no but I have to clarify. If I energize something, it's not to test it but to provide temp power, in which case I don't wire past the receptacle I'm hooking up for temp power. For lighting and smoke detector boxes I always twist and wirenut all the leads during rough-in, so for them it would be a "yes" answer. I almost always cap off both the hot and neutral of receptacle feeds (home runs), especially when I know there's going to be a GFI there.

If I were still working with metal boxes exclusively or when I do commercial, my answer would be different.
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Technically - if the neutral is landed in the panel that would serve it - energized or not - it should be capped off to reduce the risk of ground fault. Be it in metal boxes or in plastic.... Ottherwise you run the risk of paralelling the neutral through an EGC or worse - plumbing and or metal framing.
 
on the rare occurance

on the rare occurance

that I'll energize an incompletely wired circuit (just the other day, the HO asked me to make sure the front porch luminaire was on in case any kids came on halloween, but the other switch boxes on that circuit weren't made up), not only do I wirenut the grounded conductor, but I nut the ground wire as well. I don't want the tile guy, carpenter, or whoever to for whatever reason move the wires around and have the chance of an uncapped wire making it's way into the hot ungrounded conductors wire nut.

Only takes a second........twist, twist, twist
 
The result - due to several ground faults, was ~10A of sparking and current on the plumbing while someone was working near the temp main panel. This was due to a parallel path for neutral current as one of the faults was a neutral to EGC in a metal box to metal framing which also contained plumbing.
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Again please. Slowly. Dumb it down for me. In my mind, in a properly wired circuit, the neutral is grounded and no electrons should be leaking out of it downstream.
 
220/221 said:
Again please. Slowly. Dumb it down for me. In my mind, in a properly wired circuit, the neutral is grounded and no electrons should be leaking out of it downstream.
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He didnt insulate the neutral, which was carrying the unbalanced current of the load which ended up causing a phase to ground fault between the current-carrying neutral conductor(phase) & the EGC(ground) - a fault that ended up propogating to the plumbing cause the pipes were bonded.
 
220/221 said:
Again please. Slowly. Dumb it down for me. In my mind, in a properly wired circuit, the neutral is grounded and no electrons should be leaking out of it downstream.
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Electricity doesn't just take the path of least resistance to ground. It takes all paths to ground.
 
jaylectricity said:
Electricity doesn't just take the path of least resistance to ground. It takes all paths to ground.
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Yes - if you have a neutral to ground via an EGC or other path - current from the neutral will be in paralel on that grounding path. While the path may be striaght back to the main service, any diverting path can also come into play. And while it may not be a large voltage (2-5 VAC) it can be quite a lot of current. Depending on how many paths you have it will divide equally among them. So if you have 2 paths, 50% of the unballanced current will flow on both. If you have 4 paths 25% will flow equally on all 4 paths. If you say have a single phased panel fed from a wye system this can often be fairly high amperage. Or if you have a panel that is not ballance very well when under load it too can aslo be fairly high... Since voltage may not matter much when getting shocked if you become part of the path.


Some images....
un250-66.jpg


505ecm17fig4.jpg


211ecwb15fig3.jpg



An article:
http://ecmweb.com/mag/electric_heart_objectionable_current/
 
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