sparky 134
Senior Member
- Location
- Joliet, IL
We went to an industrial facility to install one additional high bay fixture. The fixture is a 1000watt MH, 480volt.
So we pipe the raceway, pull the wire, hang the fixture and I went back to the electrical room to turn off the 2p20amp CB that is feeding the existing circuit we are tapping into.
I returned and told the guy I was working with the power was off and to go ahead and make the splice. He pulls out his meter and says, "This is still hot up here."
But the existing lights on this circuit went off when I turned the CB off. This doesn't make sense. So he brings the lift down and I go up to see what's going on. Sure enough all four wires in the box are still showing 277v to ground. We had a brown, orange, yellow and orange coming into the box. The brown and one orange were taped together and the yellow and the other orange were taped together. All four wires were showing 277v.
So we go back to the panel and meter the load side of the CB that is off. We're reading 277v on both phases to ground. So now I think the orange wires are crossed somewhere and the CB is being backfed. So I turn off the CB that was hooked up to the orange and yellow network but I'm still reading 277v to ground on the original CB and the second CB we turned off.
So we trace the wires inside the panel down to the pipe they are leaving the panel in and we see that are three single phase networks in the same pipe (brown & orange, yellow & brown, orange & yellow).
I turn off the third CB and finally all six wires are showing 0 volts. Somewhere before the box we are working in the networks have gotten mis-spliced thus causing all of the backfeed problems. I believe the CB's are being backfed thru the ballast in the high bays. These fixtures have been operating this way for years.
After turning off three CB's we left about 1/4 of the building in the dark so we couldn't finish correcting the problem. We are scheduled to return on Friday to finish correcting the problem.
It's a good thing my partner remembered to meter the wires before attempting his splices.
So we pipe the raceway, pull the wire, hang the fixture and I went back to the electrical room to turn off the 2p20amp CB that is feeding the existing circuit we are tapping into.
I returned and told the guy I was working with the power was off and to go ahead and make the splice. He pulls out his meter and says, "This is still hot up here."
But the existing lights on this circuit went off when I turned the CB off. This doesn't make sense. So he brings the lift down and I go up to see what's going on. Sure enough all four wires in the box are still showing 277v to ground. We had a brown, orange, yellow and orange coming into the box. The brown and one orange were taped together and the yellow and the other orange were taped together. All four wires were showing 277v.
So we go back to the panel and meter the load side of the CB that is off. We're reading 277v on both phases to ground. So now I think the orange wires are crossed somewhere and the CB is being backfed. So I turn off the CB that was hooked up to the orange and yellow network but I'm still reading 277v to ground on the original CB and the second CB we turned off.
So we trace the wires inside the panel down to the pipe they are leaving the panel in and we see that are three single phase networks in the same pipe (brown & orange, yellow & brown, orange & yellow).
I turn off the third CB and finally all six wires are showing 0 volts. Somewhere before the box we are working in the networks have gotten mis-spliced thus causing all of the backfeed problems. I believe the CB's are being backfed thru the ballast in the high bays. These fixtures have been operating this way for years.
After turning off three CB's we left about 1/4 of the building in the dark so we couldn't finish correcting the problem. We are scheduled to return on Friday to finish correcting the problem.
It's a good thing my partner remembered to meter the wires before attempting his splices.
