First time - shorted circuit

[billconner]

I think I've been vigilant and careful in my many years of diy electrical work. (Well, overlooking my grad school time 50 years ago when I'd tie portable dimmer boards - theatre lighting - into panels - hot.) Seems I must have put a drywall screw or nail into a piece of 14/3 NM-B. Popped a breaker first time I hooked up. Then worked fine for three days. Then dead short.

Is it possible the 2-screw clamp caused the problem?

About to try to diagnose and replace wire before cellulose is blown in attic tomorrow.

 

[Copymutt]

Not likely, box entry clamps are designed to do their job. Most likely your first guess. New work? Disconnect from breaker box & begin the search. If multiple devices break those connection at their junction boxes & meter each till its narrowed down.

 

[mike93lx]

I had a clamp short out a wire on a wafer led a few years ago. 100% my fault in installation, but it did cause a problem.

Good luck with finding it

 

[sparky 1971]

If the clamp is too tight, yes it will cause a short. Is this your addition? If it's an arc fault, it might be something else. The very first time I turned on an arc fault breaker it tripped. Upon opening every single box on the circuit, I discovered a ground wire had folded back wrong and was touching the neutral on a receptacle. It could be something as simple as that. If it is an arc fault breaker, take it out and try using a regular breaker just for diagnostics. If it still trips, you have a real short. If it doesn't, it's the arc fault seeing something it doesn't like.

 

[mike93lx]

If the clamp is too tight, yes it will cause a short. Is this your addition? If it's an arc fault, it might be something else. The very first time I turned on an arc fault breaker it tripped. Upon opening every single box on the circuit, I discovered a ground wire had folded back wrong and was touching the neutral on a receptacle. It could be something as simple as that. If it is an arc fault breaker, take it out and try using a regular breaker just for diagnostics. If it still trips, you have a real short. If it doesn't, it's the arc fault seeing something it doesn't like.

You feeling OK?

First time I've seen you type out arc fault without a suggestion to throw it away

 

[Innovate1]

Narrow it down to which run of wire by disconnecting the joints - guessing you may have already done that. Check the end points. If nothing obvious there then does it go through holes where it might be caught by a nail/screw. Pull the wire back and forth a bit to check if it is free to move at each member - if it is free there isn't a nail puncture there. Or are there portions of the runs already behind drywall and other things? If it's a hard short then I would break out the TDR to find distance to the short but that's not something most people have...

 

[sparky 1971]

You feeling OK?

First time I've seen you type out arc fault without a suggestion to throw it away

That's coming but the inspection has to get out of the way first. I can't be there to bully the inspector into looking the other way so we have to temporarily follow the rules.

 

[billconner]

Well, found it. New wiring in previously unfinished garage. Is not now but will be arc fault - actually combo arc fault GFCI breaker not installed yet.

Potentially 5 segments and the short - using a vom meter - did not seem to be constant, but always between hot and ground. I *think* it was one strand of a stranded 16 in a fixture was not fully in the wire nut. Retesting and wiggling and jiggling every wire at 4 boxes, and of course looking for continuity between every combination of conductors, working again.

Makes a case for taping all wire nut connections, or at least those with stranded wire. I have generally not, disliking the leftover goo when I have to change it. Makes me fond of the wago like connectors included with some fixtures. Stranded 16 wire nutted to solid 14 or 12 is not my favorite.

Discouraging because I don't ever recall making this mistake before. Work done outside on a ladder in 40 degrees so numb fingers along with age contributed.

Thank you all for your thoughts.

 

[Innovate1]

A meter may give inconsistent results if it is not a "hard" short, meaning the conductors are in good contact. If they aren't in good contact, even a microscopic distance between, the low voltage of the meter will not jump the gap but with line voltage it will jump the gap. I hate the goo from tape when you have to go back later.

 

[nadogail]

One house I bought had a problem, it turned out to be the Lag Bolt for the seismic restraint ******** a water heater had penetrated the NM Cable feeding a receptacle.

Backed out the Lag and reinstalled it 2" higher, put some liquid electrical tape on the cable, then patched the drywall.

 

[billconner]

One house I bought had a problem, it turned out to be the Lag Bolt for the seismic restraint ******** a water heater had penetrated the NM Cable feeding a receptacle.

Backed out the Lag and reinstalled it 2" higher, put some liquid electrical tape on the cable, then patched the drywall.

oh no, don't admit to that in writing!

 

[wyliesdiesels]

One house I bought had a problem, it turned out to be the Lag Bolt for the seismic restraint ******** a water heater had penetrated the NM Cable feeding a receptacle.

Backed out the Lag and reinstalled it 2" higher, put some liquid electrical tape on the cable, then patched the drywall.

That wasnt a good idea. You cant tell if the conductors were damaged which they most likely were