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Old 03-01-2015, 12:43 AM   #1
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Default Mind boggling

OK so Im going to explain a situation that happened to me the other day. Like the title says, Im at a total loss. Ive tried to think of everything and have only been able to come up with a short list of far fetched explanations. So here it is: new construction 14 unit apartment building, one service on either end of the building. 400 amp main fusible switch feeding 2 meter stacks, one four high, one 3 high. 125a main breakers at the meters. panels in the units are MLO. so i have a guy trimming a unit and he energizes a kitchen circuit and puts in his tester. it reads reversed polarity so he comes and gets me. i begin to take the gfi out of the box and i get zapped. mind you i didn't touch anything that should have been energized. i go to the panel and pull out my meter and this is what i get:
line to line- nothing
line a to ground- nothing
line b to ground- 240
at this point i immediately go outside to the main switch. i was a little freaked and didn't say a word to my guy who was in the bathroom digging in the ceiling for a buried box. i later found out that when he stabbed his drywall saw into the box sparks flew. all the was made up at the switch box was grounds and neutrals. at this point i was almost to the switch, and when i got there i turned it off. i then tested the mains coming into the main switch. everything read normal. i then turned off all the unit breakers and turned on the main and took readings from the bus bars in the meter stack (line side of meter), normal. I then took readings on the load side of the meters, and i got the same crazy reading i got in the unit. at this point i yanked out the meters and looked for anything out of the ordinary. maybe a strand of wire that was clipped carelessly and fell in there. i found nothing. however when i put the meters back in and i took another reading everything was normal. now i know I may have not have gone about diagnosing what happened in the right way, to be honest i was about to poop myself at first. i thought somehow we had bolted the switch to the stacks wrong and switched up the lines/neutral. this was not the case. i called the poco and told them what had happened. they sent a guy out who looked at the stack, and concluded that everything was fine. its like the car that stops making the funny sound the day you take it to the mechanic. I've gone back and tested multiple times a day for a couple days now and everything is normal. this doesn't make me feel better though. bottom line the ground was energized. obviously if i don't understand what caused this there a potential it could happen again. it seemed to me as if the meters could be the problem. they are the type with a neutral. but it seems so far fetched to think a faulty meter would energize the neutral/ground (they are bonded at the main). I've thought of other possible scenarios but nothing really makes sense. thoughts, questions, comments, concerns?

Last edited by tomelectric; 03-01-2015 at 12:47 AM.
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Old 03-01-2015, 12:50 AM   #2
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You are reading voltage from the other service. It is tied into the wiring for the other service somewhere in the building branch circuits. That is why you are reading voltage with the meters removed. They are on the same phase and that is why they don't short out when you install the meters.
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Old 03-01-2015, 01:08 AM   #3
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Quote:
Originally Posted by tomelectric View Post
OK so Im going to explain a situation that happened to me the other day. Like the title says, Im at a total loss. Ive tried to think of everything and have only been able to come up with a short list of far fetched explanations. So here it is: new construction 14 unit apartment building, one service on either end of the building. 400 amp main fusible switch feeding 2 meter stacks, one four high, one 3 high. 125a main breakers at the meters. panels in the units are MLO. so i have a guy trimming a unit and he energizes a kitchen circuit and puts in his tester. it reads reversed polarity so he comes and gets me. i begin to take the gfi out of the box and i get zapped. mind you i didn't touch anything that should have been energized. i go to the panel and pull out my meter and this is what i get:
line to line- nothing
line a to ground- nothing
line b to ground- 240
at this point i immediately go outside to the main switch. i was a little freaked and didn't say a word to my guy who was in the bathroom digging in the ceiling for a buried box. i later found out that when he stabbed his drywall saw into the box sparks flew. all the was made up at the switch box was grounds and neutrals. at this point i was almost to the switch, and when i got there i turned it off. i then tested the mains coming into the main switch. everything read normal. i then turned off all the unit breakers and turned on the main and took readings from the bus bars in the meter stack (line side of meter), normal. I then took readings on the load side of the meters, and i got the same crazy reading i got in the unit. at this point i yanked out the meters and looked for anything out of the ordinary. maybe a strand of wire that was clipped carelessly and fell in there. i found nothing. however when i put the meters back in and i took another reading everything was normal. now i know I may have not have gone about diagnosing what happened in the right way, to be honest i was about to poop myself at first. i thought somehow we had bolted the switch to the stacks wrong and switched up the lines/neutral. this was not the case. i called the poco and told them what had happened. they sent a guy out who looked at the stack, and concluded that everything was fine. its like the car that stops making the funny sound the day you take it to the mechanic. I've gone back and tested multiple times a day for a couple days now and everything is normal. this doesn't make me feel better though. bottom line the ground was energized. obviously if i don't understand what caused this there a potential it could happen again. it seemed to me as if the meters could be the problem. they are the type with a neutral. but it seems so far fetched to think a faulty meter would energize the neutral/ground (they are bonded at the main). I've thought of other possible scenarios but nothing really makes sense. thoughts, questions, comments, concerns?
First, please break your long post up some. Use the enter button a few times, make paragraphs with spacing between, etc. It is very hard to read.

Now from what I could read, how is it you say nothing was made up but grounds and neutrals but you needed to turn off breakers in the panel?

Maybe I missed something but it was hard to tell when you went from one thing to the other without spacing or breaking up your sentences some.

I don't mean to pick on you. I just found it would have been easier to help answer your concerns if I/we could understand what you meant.
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