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Old 11-29-2011, 12:25 PM   #1
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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.


Last edited by Perry401; 11-29-2011 at 12:32 PM.
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Old 11-29-2011, 01:33 PM   #2
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Commercial Building with 277 Volt Exit & Emergency Lights


There is only ONE correct and valid answer to this. Have the owners HIRE AN ELECTRICIAN!
This is not handyman or DIY work. Not even close.

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Old 12-03-2011, 10:26 AM   #3
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Commercial Building with 277 Volt Exit & Emergency Lights


I totally agree w/speedypetey. 277v is very dangerous. need a pro
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Old 12-03-2011, 11:10 AM   #4
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Commercial Building with 277 Volt Exit & Emergency Lights


FYI - Exit signs and emergency lighting need to work when the power is off. That means batteries. And if there are not batteries in each light/exit sign, then there would be a central inverter and batteries somewhere like this...
http://www.emergencylighting.com/category/Inverters.cfm

And there may be a specific company in your area which services those units. Could be an "electronic" problem in that unit.

About Inverters...
http://en.wikipedia.org/wiki/Inverter_(electrical)
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Old 12-03-2011, 11:14 AM   #5
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Commercial Building with 277 Volt Exit & Emergency Lights


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I totally agree w/speedypetey. 277v is very dangerous. need a pro
Another myth we can dispense with here today. 277 volts is no more dangerous than 120 volt, 480 volt or 600 volts. How this old wives tale got started is hard to figure. It might be that 277 sounds scary.
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Old 12-03-2011, 01:19 PM   #6
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Commercial Building with 277 Volt Exit & Emergency Lights


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Another myth we can dispense with here today. 277 volts is no more dangerous than 120 volt, 480 volt or 600 volts. How this old wives tale got started is hard to figure. It might be that 277 sounds scary.
Come on John, do you really feel 277v is no more dangerous than 120v?
Why is it that the higher the voltage the stricter the rules, codes and safety procedures?
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Old 12-03-2011, 01:23 PM   #7
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Commercial Building with 277 Volt Exit & Emergency Lights


Couldn't you trace the conduit with the known good circuit back to the panel? You stated that there are two circuits in the same conduit. Wouldn't the open circuit be there as well? You could always tie the exits into the emergency lights as they both require constant power. Don't see why that transformer had anything to do with it unless the exit signs are 120v, in which case wouldn't be right because you can't mix voltages in same conduit.
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Old 12-03-2011, 01:40 PM   #8
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Commercial Building with 277 Volt Exit & Emergency Lights


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Another myth we can dispense with here today. 277 volts is no more dangerous than 120 volt, 480 volt or 600 volts. How this old wives tale got started is hard to figure. It might be that 277 sounds scary.
I much rather get a 120V shock then a 600V shock. I have a very good chance of going home at the end of the day from a 120V shock. 600V has a much better chance of putting me in my wooden home 6 feet under the ground.
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Old 12-03-2011, 10:58 PM   #9
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Commercial Building with 277 Volt Exit & Emergency Lights


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Another myth we can dispense with here today. 277 volts is no more dangerous than 120 volt, 480 volt or 600 volts. How this old wives tale got started is hard to figure. It might be that 277 sounds scary.
I'm not sure I've ever seen you post something incorrect on here before, but this certainly isn't true. As you well know, ohm's law dictates how much current flows through your body when you touch something electrified. Higher voltage results in higher current flow, and therefore more injury. Even worse, resistance of your body is nonlinear and decreases with higher voltage, because your skin breaks down from heating. 277V will not just push 2.3 times more current through your body than 120V, it will push much more. You also know that power (heating) is I*V, or V^2/R. Thus, 277V will cause at least 5.3 times more burning of your tissue than 120V - and that doesn't even take into account the nonlinear resistance of your body. 277V is way more dangerous. 120V only accounts for more fatalities because it's more common.
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Old 12-03-2011, 11:20 PM   #10
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Commercial Building with 277 Volt Exit & Emergency Lights


When 277 is under control, it's certainly no more dangerous than 120, but it has the ability to cause far more harm if it gets out of hand.

Around here, with extremely dry climate, 120 won't 'lock you up', but 277 will. You have no control over your muscles.

Also, it'll make a way bigger bang when it's shorted out.

I work with 4160 and higher on a regular basis, even those voltages are completely safe if they're under control.

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Old 12-03-2011, 11:24 PM   #11
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Commercial Building with 277 Volt Exit & Emergency Lights


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another myth we can dispense with here today. 277 volts is no more dangerous than 120 volt, 480 volt or 600 volts. How this old wives tale got started is hard to figure. It might be that 277 sounds scary.
how the hell do you hold a licence !
With a totally ignorent statement like that !
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Old 12-04-2011, 01:43 AM   #12
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Commercial Building with 277 Volt Exit & Emergency Lights


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Also, it'll make a way bigger bang when it's shorted out.
Another good point. 277V is the lowest system voltage that commonly poses an arc flash hazard. Short the busses in a 240V panel and you get a good fireworks show, but can likely turn away in time to avoid serious injury. Short the busses in many 277/480V panels, and you get an explosion of vaporized metal that literally ruins your life, or burns you to death.
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Old 12-04-2011, 05:35 AM   #13
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Commercial Building with 277 Volt Exit & Emergency Lights


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how the hell do you hold a licence !
With a totally ignorent statement like that !
JV is a pretty smart guy. This comment is a bit out of line.
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Old 12-04-2011, 11:19 AM   #14
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Commercial Building with 277 Volt Exit & Emergency Lights


My point was all voltages can be deadly. Not just 277 volt and up. Of course the higher the voltage, the more damage can result. But this is a DIY site. Are we going to start telling everyone here that 120 volts is safe? But 277 is not safe?
Electricity is inherently dangerous regardless of voltage. That was my intention.
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Old 12-04-2011, 11:48 AM   #15
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Commercial Building with 277 Volt Exit & Emergency Lights


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JV is a pretty smart guy. This comment is a bit out of line.

The guys location is Australia ...they tend to be blunt down under.. and offer no explanation for their comments.....

Perhaps JV could have chosen a better way to explain his thoughts but the point is all voltages can kill you. I think one of the better myths is that high voltage will knock you away and break your contact.....I found this to be true with 480 .. once ... I hope there isn't a second time.

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