Panel screw to energized feeder fault

[Kdog76]

Had an oops... We were finishing up a service change on a two-family today. As my helper went to put one of the panel cover screws in it nicked the feeder cable on one of the lines. Went in thru the insulation enough to make contact, & held long enough for the end of the screw to melt off which then cleared the fault. Luckily no one was hurt, and the fault cleared on its own. I called the utility back to pull the meter so we could cut our feeder off at the nick & then land our feeder back on the main again. Luckily the AL feeder was long enough. My helper (long time electrician also - recommended just taping it, but I wasn't to sure about that idea...)
Both of our faults for 1) routing the feeder cables right behind the screw opening & not tucking the wires to the back of the panel & 2) not checking before running those screws in.
I do have one question. No one was home at the time so I didn't get to check if any electrical appliances in the units may have been damaged. I wasn't in the basement at the time so I'm not sure how long the screw had been making contact. Only that it was for enough duration to melt the end of the panel screw off. Just a little worried, any reassurance would help.

 

[sparkchaser1961]

I can't see why any other equipment would have been damaged. Sounds like a ground fault to me, you know line to panelbox. Probably the only damage was to the feeder and the panelbox.

 

[Kdog76]

Yes, the panelbox had the typical black arcing residue next to the feeder - and the feeder that was damaged was cut off at the nick-point & re-oxyed... If that's all that happened I will count myself lucky. A valuable lesson learned. Thanks for the reply.

 

[sparkchaser1961]

Yes, the panelbox had the typical black arcing residue next to the feeder - and the feeder that was damaged was cut off at the nick-point & re-oxyed... If that's all that happened I will count myself lucky. A valuable lesson learned. Thanks for the reply.

I did this one late afternoon. miles from the shop. I screwed through the service wire and took power out on Friday. Had to get the poco in, the whole works. Late evening when i finished. everybody was waiting for me so they could use their camp for weekend.
been there done that got a t shirt.

 

[LBwIReman2]

Do you remember if any of the branch ckt breakers were on at the time of the fault? If not, then you are in the clear, if so, then cross your fingers. Voltage sag under 100 volts for lots of electronics can be bad if it lasts longer than a second.

 

[Kdog76]

All the breakers were on, but no one was home at the time - so hopefully not much was turned on at the time. TV's & stereos were probably off. Don't know about computers, fridge, etc.

 

[LBwIReman2]

I was working on a house one time where i had to shut off power to connect up a C.F. in an attic box. However their sub panel was hidden somewhere in the house (found it later behind an expensive painting), the computer was off, so i thought it would be safe to kill the main out back. Did that, did my work. Got a call from the HO that evening and their comp wouldnt turn on. Apparently it created a transient that killed the power source. Luckily nothing else was wrong. Food for thought.

 

[alfiesauce]

I did this in front of a HO once...
It was fed of a farm service and blew the main quickly. Thankfully.

 

[Kdog76]

I did this in front of a HO once...
It was fed of a farm service and blew the main quickly. Thankfully.

This was on the line side of the main (before the main breaker). The transformer would have to burn out before you lose voltage. No breaker protection at all. Luckily the panel cover was on with a few screws already to contain the arc flash...

 

[ZZZ]

Do you remember if any of the branch ckt breakers were on at the time of the fault? If not, then you are in the clear, if so, then cross your fingers. Voltage sag under 100 volts for lots of electronics can be bad if it lasts longer than a second.

I'll remember to never ask you for reassurance

 

[active1]

I was finishing up a job late one day. It had a new panel someone elce wired and put the cover on but was missing a screw. I found the proper machine screw on the floor and went to put it in. Being the first time that panel had a screw in the hole it went in the normal harder at first. Just when I thought it was starting to go in nice and was almost tight - Buz bam! Besides one of the feeders I replaced the cover because of the melted and burnt marks around the screw.

One thing I always check now.

 

[Kdog76]

Thanks for all the replies here. It's the following morning, and I haven't got any callbacks yet. Maybe I thought I'd stop in at the job today, see if anyone's home just to check that everything is working. Either way I've learned the lesson, I know my helper learned, and hopefully anyone reading these posts if they did not know already, will now.