Had a close call with a 277v lighting circuit in a Chicago high-rise last month

We were swapping out old fluorescent fixtures for LEDs on the 15th floor. My apprentice went to test a circuit he thought was dead, but the building's lighting panel schedule was wrong. His meter read 277v to ground when he expected 120v. The shock threw him back about three feet, but his gloves saved him from worse. Now I make my crew verify voltage with two different meters before anyone touches a wire, no matter what the prints say. How do you guys handle bad panel schedules in old buildings?

4 comments

4 Comments

murphy.aaron2mo ago

Honestly, how do you even start tracing wires in a mess like that? Tbh I'd be worried about hidden junctions or abandoned lines still being hot. Sounds like a nightmare to sort out.

rowan_thomas846d ago

Oh man, that "treat every wire like it's hot" rule is gospel. I did a favor for a buddy last year, helping clean out an old workshop his dad had owned since the 80s. Found a junction box that literally had wires snipped off and just taped over with black electrical tape, no marrettes, nothing. I touched the tape with my voltage tester and it lit up like a Christmas tree. Someone just left live 120 in there thinking "future me will deal with it." The "test, test, test" habit is the only way to stay safe. I always carry a known good outlet strip or a plug-in tester just to double check my meter is reading right. It's annoying but losing a finger over someone else's lazy panel labeling is not a risk I'm willing to take. And yeah, "spare" and "misc" on a panel are basically a dare from a past electrician. I'd rather spend an hour mapping things out with a toner and a helper than guess based on a sticker that might have been wrong since day one.

-1

patricia_gonzalez2mo ago

My uncle's an electrician and he told me a story about a hospital rewire where the panel labels were from a renovation in the 70s. They found a whole bank of circuits marked "spare" that were actually live feeds to the old nurse call system. His rule now is to treat every unknown wire like it's hot until you prove it's dead with your own tester, then prove the tester works on a known live source right after. It's that "test, test, test" habit that saves fingers.

dakota4152mo ago

Spare" is the most terrifying word you can read on a panel label, right up there with "miscellaneous." Of course the 70s renovation crew just slapped that on there and called it a day, probably thinking future people would have cool x-ray vision. Your uncle's rule is the only way, because trusting a faded sticker from the disco era is a fantastic way to make your day very, very exciting.