i have a warehouse......60,000 square feet (300'x200'). Planned on ordering 277v lighting throughout but our engineer said we should use 480v lighting. said something about not having to run a neutral or something like that about harmonics.
I know that there are HID fixtures which can run off 480. As far saving money on copper wire...its probably going to be a wash. Although you do not have to run a neutral, you still have to run two current carrying conductors plus a ground wire (3 wires per fixture). I'm not sure about the harmonics...I'm assuming the fixtures are single phase, not 3 phase.
First, be aware that there are some mounting height restrictions that limit use of 480V lighting in NEC-land.
If you plan to power this lighting from a large 480V transformer, then the 277 V is a big pain in the neck. The use of 277V line-to-neutral loading requires that a neutral be provided in the incoming switchgear and that it be carried all the way down to the lighting panel. The neutral loads complicate the ground fault protection especially if you have a double-ended substation. You also run the risk of a ground fault in a lighting circuit taking down a large chunk of your 480V system.
Use of 480V fixtures will allow more fixtures per circuit and allow longer circuit runs.
If you want 277V just for lighting, a good solution is to provide a small 480 delta - 480/277V wye transformer.
Harmonics need to be considered, but I don't see that as a reason to not use 277V. There are other reasons why 277V is often a nuisance.
If the lighting is either all on or all off, switching may not be an issue. If you want to use just part of the lighting at times, switching is cheaper with 277 V.
You can use single pole switches for 277, you need double pole switches for 480 volts.
Switches for 277 are readily available. 2 pole 480 volt switches are not as common and may be more expensive.
277 uses one breaker pole per circuit, 480 uses 2 breaker poles per circuit. For both 277 v and 480 V you can use equal 3 pole breakers if you don't want to control smaller circuits individually.
yours
Thanks for the input, guys. FYI, we're planning to use the following fluorescent product and it sounds as if 480V single phase is indeed the way to go. Thanks again...and here is the fixture...
