# 277V Rated / 240V Provided



## Kuku (Mar 23, 2009)

Question of the day: will a lighting unit (e.g. an exit sign) that is rated for dual voltage 120/277 work properly on a circuit that is 240V single phase?

Good luck!


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## Flyer_PE (Mar 23, 2009)

Is your 240 line to neutral or line to line? I'm used to seeing 240 as two hot conductors each running 120V from line to neutral.


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## Kuku (Mar 23, 2009)

Circuit is being provided from a 2-pole breaker in a panelboard that is 120/240 single phase.


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## geofs_PE (Mar 23, 2009)

If you have a typical 240 single phase with grounded center tap service, you would have single phase 120V to neutral. If this is the case couldn't you connect it 120V?


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## geofs_PE (Mar 23, 2009)

Can you replace the 2-pole breaker with a single pole and power the light with 120V?


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## Kuku (Mar 23, 2009)

geofs said:


> Can you replace the 2-pole breaker with a single pole and power the light with 120V?


For the sake of arguement, let's say that the lights were 400W metal halides, and there were quite a few of them. So you want to have as many of them as possible on the same circuit to avoid having to use larger lighting contactors, etc; thus powering them at 240V. The exit signs and emerg. egress lights have to be on the circuit serving the room, so where does that leave you?


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## geofs_PE (Mar 23, 2009)

It must be a large room to have "quite a few" 400W MH fixtures in it. Quad-ballast (277/240/208/120) or multi-tap ballast fixtures are quite common. As for the exits and emergency egress fixtures, I've never tried powering a 277/120V rated fixture with 240V but since the voltage is 13.4% less than rated voltage, I don't think it would work . If you were to use quad-ballast fixtures @ 240V, I don't know of any code issue arising from splitting the exits and emerg. fixtures evenly and powering half from each 120V leg of the 240V circuit. You would need a neutral conductor for each 120V leg.

You could also consider an autotransformer to boost the 240 to 277 but getting the correct voltage fixtures would be much easier and possibly cheaper.


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## Freon (Mar 24, 2009)

You might need to pop'er open and check the ballast. But Geofs' comment about running it at 120V is most likely the best solution.

Freon


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## chaosiscash (Mar 24, 2009)

Are you sure the exit signs aren't dual rated for 120 or 277? Most I've seen are. Either way, as others have said, you need to either buy the right voltage light or provide the correct voltage to it.


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