277 Volt Lighting vs. 120 Volt Lighting

[richanton]

I am designing an industrial facility that has some office areas. My plant lighting is 277 volts. If I also use 277 volts in the office areas, do I need to use low voltage switching. Normal lighting switches are rated 277 volts, so I guess its OK to use them, but it just bothers me to have that voltage in an office environment. I can't find anything in the NEC that says I can't use it.

 

[WoodrowJWeen]

Most larger office buildings in the US have 277V lighting.

 

[wareagle]

If you are concerned about safety, a properly installed system per the NEC would be just as save as a 120 volt system. You are going to have to use a step down transformer for the 120 volt load.

 

[mpparent]

Well,

If the office dwellers don't start taking the switch plates off and fiddling around, they should be ok.



Mike

You can use 277V for those areas. No problem at all.

 

[BJC]

richanton
Several manufactures make interposing relays so all the switching is done at 24 volts. The system have the capability to utilize other componets such as motion sensors, bilevel switching, hand held remotes, daylight sensing, time out switches etc. etc. The last office I did we used WattStopper stuff. It worked good, there are similar systems. I would call the local peddler and tell him what your doing and let them do the detail work ( your still in responsible charge).

 

[richanton]

Thanks for the tips. I think I will make a call to the local lighting guy and get his 2 cents.

 

[resqcapt19]

Note that if you have multiple switches in a common switch box and the switches are supplied by different phases, then 404.8(B) will require a divider in the box between the switches. This code section says that the voltage between terminals on devices in a common box, must not exceed 300 volts unless permanent barriers are installed.
Don

 

[mc5w]

I would not use 277 volts for lighting in a bathroom or swimming pool area, but anything else is fair game.

The reason for box barriers is that when a light switch turns off it emits ionized gas. If there is not a grounded barrier between different phase switches you can get a 3-phase arcing fault. What the grounded barrier does is to discharge the ionized gas before it reaches another switch.

The biggest problem with 277 volts in offices is that you can have 1,200% inrush current for electronic ballasts. This tears the heck out of light switches. See my website http:// home dot earthlink dot net /~mc5w and click on badnewsballasts.txt for more details.

 

[alehman]

Direct switching of 277V lighting circuits was prohibitied by the NEC many years ago, but now it is almost universal practice. There may still be a few local jurisdictions that don't permit it.

I've seen one or two 277V light switches blown to pieces by a short circuit. Something to consider.

 

[mc5w]

277Y480 will get your attention if there is a short or similar problem, but so will 120Y208 that comes off of a big expletive transformer.

Using 200 amp class J time delay fuses ahead of your lighting panelboards helps a lot. The fuses DO coordinate with the breaker if you should pinch a wire between the panelboard cover and the box - Bell System wire management methods will prevent that such as sticking telephone distribution posts inside the panelboard and tying the wires to them. The class J fuses should only blow if a forklift truck driver shears off a 40 amp or larger power feed.

In actuality there are more fires involving 120 volts partly because there were a lot of junk circuit breakers on the market. My experience with Federal Pacific is that they worked right when new and then developed arthritis. Exercising the breaker restores normal operation such as when changing broken outlets. Then, the customer discovers that they have 30 amps of load on a 20 amp circuit.