||11-29-2011 01:25 PM
Commercial Building with 277 Volt Exit & Emergency Lights
Perhaps one of the "old timers" can suggest a solution for a current problem. There is a commercial building where I do some of my work which has 277 3 phase used mostly for lighting circuits. There are a series of emergency lights and exit signs mounted appropriately through out the building. The two systems share conduit runs at the ceiling level with separate drops to each exit sign or emergency light. The exit signs are all connected to two wires in the conduit (black and grey). The emergency lights are also connected to two different wires in this conduit (again black and grey). We have found the breaker for the emergency light circuit, but not the exit signs. We have attempted to follow the conduits and see no other point where a power source may be provided for the exit signs.
To make matters worse, there seems to have been a lot of failure of breakers in the old ITE breaker box, and the circuits, which were neatly numbered with wire tags are now scrambled to different breakers. The wire from the "Emergency light" breaker is a newer THHN type with glossy plastic coating in the breaker box and up into the ceiling. All other wires use a totally different insulation. I suspect that this wire was re-run at some time in the past. We have some electrical drawings for the building, but they are incomplete and not of much help with these circuits.
About 6 months ago, someone plugged a high-amperage power-washer into an outlet which was supposed to be dedicated to a time clock. This caused an electrical fire when a 500 VA transformer mounted in a tiny box with NO fusing on the primary or secondary melted down. At the time, the source of the power to this transformer could not be found, so an electrician simply cut the still hot leads to the transformer and put wire nuts on them, saying he thought they were on the exit sign wiring, and elimination of the transformer would not hurt anything.
Now all exit signs have failed, and there is no voltage at any which have been tested, so I assume there either is a "hidden" power source for the exit signs with a blown fuse or breaker, or that there is a melt-down in the power feed for this circuit. At the same time, the emergency lighting circuit is still hot and working. What seems odd is that it would seem to me that if exit signs and emergency lights were powered from the same panel, they would share the common "grey" wire, instead of having two separate wires since the neutral would never carry more than the load of the difference of the two circuits. At the same time, the "NEW" wire from the breaker into the ceiling is suspicious and the rearrangement and scrambling of breakers makes me wonder if perhaps there had been separate breakers at one time for each circuit and these had been somehow combined. I also wonder if the "melt down" of the unfused transformer may have overheated a conductor which caused damage to the insulation.
Can anyone give me some advice on how to proceed. I want to keep things safe. The building was built in 1975 if that is any help.