Hello, I was called out to a 26 unit apartment building for a complaint of appliances catching on fire in 1 unit. I met the fire dept. on site. At that time nothing could be found wrong electricly. All conections were checked and tightned in meters and in the affected apartment. POCO was on site and all voltages checked out good on both ends. It was decided to be a loose nuetral in the apt. sub panel.
3 days later I get the same call, but on a building wide scale. 13 of the 26 units having the same problem. I have now found half of my nuetral current to be on the GEC, indicating an open nuetral. Again brought in the POCO. The building has 2 800amp 1p services. Both have the same problem. We have megged the underground from poco transformer to meters. No problems found. Thermal camera used to check underground for hot spots. None found. We ran a temp nuetral from transformer to service and still had the same problem. I dismantled the meter banks, checked and tightend everything. Still have same problem.
What is really getting me on this is that my voltages have never been bad like you would see with an open or bad nuetral. Tomorrow I am planning on putting my recorder on the service for most of the day. While there, we will check all sub panels in each unit.
I am at a loss as to why I have good voltage but have current on the ground. Any body had this problem before? Thanks, Richard
Considering you should have zero neutral current on your ground, you need to look for a bonding jumper in a sub panel that doesn't belong, or a neutral to pipe nick, that sort of thing. Maybe a ground landed on a neutral bus. I know that you really meant that seeing half the current on the ground meant that it showed roughly the same impedance as a return path and thusly shared the current equally. So if you can work your way away from the source with a clamp-on on the ground and see the current drop to what should be zero fault current, you know the neutral to ground oops is behind you. Joe
Last edited by JoeTestingEngr; 10/30/0709:54 PM. Reason: changed my landing direction
I had a simular problem with PECO in PA.(no fire) They had three different crews check out the transformer, before one found the problem with their neutral connection.(under the tape) It is like anything else, it all depends on how much effort the utility crew is willing to put into their job.
i had a similar problem at a friends house turn on the lights in the kitchen & they looked liked like spot lights. called power company out they cleaned neutral atb pole , then all was fine so we thought.come home about 12 that night & notice security light not burning.go in the house turn on lights in kitchen ,look like spot lights again.call power company again.they check things at meterbase & get 240 too neutral. get in bucket truck & check at pot ^ find same thing,now mind ya this is 2 a.m. in the morning. they finally find that the neutral connection inside the pot is bad. replace pot with a new one cut it back on ,security light comes back on, voltage is back to normal. they also pay for his appliances that were burnt out due to the overvoltage.pot is sent too scrap yard!does these apartments have two seperate pots or pad mounts? if there 800 amps each i would guess there would be 2.
This guy said he has no bad voltages. The neutral connections are therefore OK. Like Joe said, he has paralleled the neutral with the equipment ground.
Look for a connection from neutral to ground somewhere other than at the service. Probably one or all of the subpanels. The neutrals and grounds should all be separated, never to touch, except at the service.