these fixtures are old and at the end of thier life, most people cannot use these fixtures because of the 277 volt industrial voltage so they build up. The reason there is so much 277 volt fixtures is because large plants change all the fixtures out at once during planned outage so it will not stop productions. RE: why 277 volts for lighting? advidana (Electrical) 1 Apr 05 04:19 Incidentaly the most economical shop fixture (light output per $ cost) is a 400w metal halide high bay fixture - cost about $90, output equivilent to three 8 foot two tube flourescents. Home Depot offers a complete panel with breakers for 120/240 single phase for about $125, while for a 200A 277/480 panel with breakers your cost would be aboput $800-$1200, and you would still need to set a transformer and 120/208v switch gear for receptacles, probably another $1000 minimum.įor you, the economical solution is to use either 120 volt fixtures, or try to find used fixtures with a multi-tap ballast (the fixture will operate on 120/208/240/277 volts, just connect the proper wire). I might add that if you did get 277/480 you would not be happy with the cost of the switch gear - it goes up by a factor of five or so. The reason your power company doesn't want to provide you with 277/480 is that the transformer they must set to serve you is expensive - there are no small 277/480 transformers available to them since the transformers of this voltage rating are normaly large enough to provide a large building or industrial shop and the power company doesn't want to waste a perhaps $10,000 transformer to provide a customer who will only be paying perhaps $100 per month. It increases the cost of the installation to provide other loads through the transformers since the transformers and associated switch gear would be larger. Transformers are set to provide 120/208 for receptacles only, normaly. In a large building all possible loads are either 480 three phase or 277 (to neutral) single phase, including lighting. The first number the phase to neutral voltage, and the second the phase to phase voltage. Standard three phase low voltages in the US are 277/480, 120/208, 120/240 three phase(special and dying) and 120/240 single phase.
In a large building it is more economical to use a higher voltage for distribution since voltage drops are less (if you double the voltage, the current is cut in half AND for a 3% voltage drop the permissable drop is doubled so for a given wire size the allowable run distance is multiplied by four - the elctrical contractor saves money for both wire and number of branch circuits). The answers given are all accurate, but let's put the whole soultion together. RE: why 277 volts for lighting? davidbeach (Electrical) 29 Mar 05 11:27 I'd like to be able to justify to them why they should give me the drop (" i have the following 3 phase motors on machines, and my shop lighting is 277 volt").but I don't know how you power 277 volt lighting, or if its reason for being is related to 3 phase.
They run their power lines right across my farm and maybe 30' from the barn. I am trying to put together a case for the local power company to provide a 3 phase drop to my barn. So- how are 277 volt fixtures wired in a commercial setting? And is it reasonable to consider powering them somehow from 240 single phase either directly or via a stepup transformer?
Is the concept that you get 277 volts across 2 legs of 3 phase power? I don't think that is the case.ĭo they run these through transformers? If that is the case, that seems really silly because you loose effieciency in a transformer, not to mention being another point of failure and fire hazard. Why do so many commercial buildings use 277 volts for their fluorescent and metal halide lighting power? Much of the surplus light fixures one comes across are 277 volts.
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