277 Volt Luminaire Ballast on 240

[tom baker]

OK, a question from a student. wonders why a 277 volt ballast - neutral and hot works (for ten years) on a 240 volt supply. I said the neutral is not a neutral, the ballast does not care about polarity, but the 277 volt ballast works on the lower voltage, of course it may not have the same mA output to the lamps.
What says the forum?

 

[mdshunk]

I've seen guys take old 277 fixtures from energy retrofits home and connect them at 240 to light their shops. Apparently, they work just fine. Not something I'd do for money. The ballasts must have quite a tolerance.

 

[frenchelectrican]

I did see them work on 240 v circuits but however the bulbs will be dimmer depending on the type of ballast itself and also if try to restrike hot bulb it will be more tougher due lower supply voltage vs standard 277v is.

IMO i am not too crazy with it either i rather have them to use the proper ballast to run the luminaire instead of " crazy setup " which i gernally stay away from it.

Merci,Marc

 

[infinity]

The fact that one system (277 volt) uses a grounded conductor and the other one doesn't is irrelevant. The ballast sees either 240 volts or 277 volts. The only difference is how well the ballast can tolerate a voltage lower than it's normal operating voltage.

 

[drbond24]

Most of the ballasts I've seen say they will accept +/-10% of their rated voltage, but then the dropout voltage is very low (~135 V). They must be able to take quite a bit of variation.

 

[Lxnxjxhx]

A ballast converts a constant voltage source into a constant current source, and this seems to be in keeping with that kind of design.