Close Call

[jeff43222]

I was on a troubleshooting call today where the garage circuit stopped working recently. Breaker tripped immediately or almost immediately upon closing it. So I shut off power and opened up boxes to look for any obvious shorts. I found none, so I proceeded to narrow down the location by disconnecting the circuit incrementally. Eventually, with all the boxes open and everything connected, I closed the breaker without it tripping.

Next step was to troubleshoot it while it was hot since the garage was now working but the lights (on the house with three-way switches in the house and garage) still weren't. I checked the three-way switch in the house by carefully holding the yoke while testing the travelers. Then I noticed it wasn't a three-way switch at all! Some clown wired one of the travelers to the ground screw, thus energizing the yoke when that traveler was switched on.

I was wearing my EH-rated shoes today, which is probably why I never even felt a jolt. This was not the first time I came into contact with something hot that shouldn't have been hot, but those times I was wearing my EH shoes, too. Money well spent, as far as I'm concerned.

 

[charlie b]

Thanks, Jeff. The best part of that story was that you were able to tell it.

 

[petersonra]

Where I used to work, my cubicle was across a short hallway from where a newly minted electrical designer worked on his drafting board.

One day as I was coming back from a coffee run, I happened to look at what he was drawing. He had drawn a motor start-stop circuit so it would only run while the start button was held in.

I pointed out the need for a seal-in contact. He agreed that he had missed that and would add it in. A short time later I noticed that he had drawn the seal-in contact in parallel with the coil.

He was eventually promoted to PM.

 

[Rockyd]

Wow! What Charlie b said...Amen!

 

[George Stolz]

Jeff, glad to see you're still with us, despite the homeowner's best efforts.

So, where did they put the EGC that was supposed to go to the switch?

While you still have the circuit fresh in mind, what exactly was the short?

 

[jeff43222]

Here's what I was able to figure out:

The circuit HR was 14-2 NM going to a nearby j-box. From the j-box were two 14-2 NM cables (not UF) going underground to the garage, and one 14-3 NM cable to the "three-way" switch in the kitchen. In the garage, it looked like one 14-2 cable from the house provided power, while the other provided travelers back to the j-box. Inside the j-box, the travelers were connected to the 14-3 hots, and the neutral from the HR was connected to the neutral on the 14-3. Inside the kitchen "three-way" switch box I found one traveler connected to the ground screw on the switch, the other traveler connected to one of the live screws, and something going presumably to the lights connected to the other screw.

The neutral and ground were not connected to anything. I found evidence of arcing burns on the neutral and ground wires, so as far as I could tell, the traveler connected to the ground screw energized the metal box, but since it wasn't properly grounded, nothing happened unless the loose bare ground happened to touch the box. The first time I closed the breaker, it tripped immediately, but the second time it buzzed for a second or two before it tripped. This seems to support my "loose ground" theory.

I replaced the single-pole switch with a proper three-way switch, but the three-way function didn't work. The switch in the garage had no effect on anything, but the three-way in the house acted like a single-pole switch. I have no idea how the lights were connected with neutrals.

 

[ramsy]

The problem with EH rated boots is they don't help the most common short thru the heart, between your hands. If doing this hot is unavoidable, maybe wearing a comfortable pair of gloves is a good idea.

Last week, I came across a 3-way to 2-way switch, box wires taped together without wirenuts, with less than 3 inches of wire to work with. Before I realized what was going on, the Ohm function on my meter was found fried. Figuring this out hot was the last thing on my mind. Something Georgestolz said about ringing-out three ways stuck with me almost a year later. So, I broke down on and went shopping for a backup meter.

After my tic-tracer ID'd the one common hot for both three ways, I de-energized again to ring-out travelers, found more ohms going thru lighting ballast, and Zero thru travelers, landed common on its mark, lit breaker, and the switches worked perfectly.

 

[hillbilly]

Where I used to work, my cubicle was across a short hallway from where a newly minted electrical designer worked on his drafting board.

One day as I was coming back from a coffee run, I happened to look at what he was drawing. He had drawn a motor start-stop circuit so it would only run while the start button was held in.

I pointed out the need for a seal-in contact. He agreed that he had missed that and would add it in. A short time later I noticed that he had drawn the seal-in contact in parallel with the coil.

He was eventually promoted to PM.

petersonra....I know that I'm mis-understanding you.
You say that he had drawn the seal-in contact in parallel with the coil.
By "seal-in contact"...do you mean a auxiliary (N/O) contact on the motor starter?
By "coil"...do you mean the motor starter coil?
If so, how would you wire the holding circuit?
Just curious
steve

 

[realolman]

Sorry, I couldn't help it... I was hyp mo tized

 

[petersonra]

petersonra....I know that I'm mis-understanding you.
You say that he had drawn the seal-in contact in parallel with the coil.
By "seal-in contact"...do you mean a auxiliary (N/O) contact on the motor starter?
By "coil"...do you mean the motor starter coil?
If so, how would you wire the holding circuit?
Just curious
steve

Nope. Thats the way he drew it in. It would have tripped the circuit the first time it was energized.

My point, I guess, was that even people who know better some times do bone headed things.