480V lighting or 277v

[qms006]

I have to wire up some site lighting and I'm thinking it would be better to wire it up at 480v rather than 277v due to voltage drop and ability to get more fixtures on a circuit. Also, whats the typical installation - run from a 3p breaker and alternate phases or run 2p circuits? One more, if going with the 3phase option is there a maximum circuit/breaker size (30A, 40A, 50A etc.)?Any body have any thoughts on this.

 

[Jim W in Tampa]

I have to wire up some site lighting and I'm thinking it would be better to wire it up at 480v rather than 277v due to voltage drop and ability to get more fixtures on a circuit. Also, whats the typical installation - run from a 3p breaker and alternate phases or run 2p circuits? One more, if going with the 3phase option is there a maximum circuit/breaker size (30A, 40A, 50A etc.)?Any body have any thoughts on this.

So there goes the shared neutral. RETHINK bad idea

 

[SiddMartin]

I would go 480v, 2P breakers, balance the phases. As far as maximum brkr size, IMO I would limit it to 30A, usually you will have multiple contactors, and the contactors our rated in Amps. The largest I have installed has been a 40A rated contactor for site lighting. (Strip malls, Shopping Ctrs). Plus, larger breaker, larger wire, larger pipe. etc..

 

[StephenSDH]

I wouldn't hesitate with using the 480v. Make sure when you calculate voltage drop you are not doing it based on your total load and the total length of wire. Calculate the voltage drop light by light, decreasing load with each light. You can run a larger wire to the first light to reduce VD, and then reduce wire size as the load reduces.

 

[buldogg]

So there goes the shared neutral. RETHINK bad idea

What neutral?

 

[masterinbama]

I would go with 480 on 2 poles and fuse each ballast. I worked on a large shopping center here and the ballasts weren't fused. One bad ballast could take out several poles. Made it very hard to find the culprit.

 

[mivey]

If you have a lot of lights, 480 if you can. It solves a lot of volt drop problems (losses too).

You may find you can get by with one circuit, but if there is a lot of load, it is better to balance the loads between the three phases.