Once you apply a voltage(240 for example)to a self-configuring multi-volt fluorescent ballast that has only 2 input leads (the type that automatically detects the applied voltage, and sets itself accordingly), can you then apply another voltage (120 for example), or is the voltage configured permanantly the first time?

Thanks and Happy New Year to all!

John (Redsy)

I would check with the maker to be sure ... but I believe you can change to a higher voltage - but not a lower.

I'm only guessing, but I'd say such a ballast would have to have some kind of memory mechanism to do that (be limited to only the first voltage applied). It would seem to me that it would be easier to just make a solid-state circuit that does constant average current over a reasonable voltage range (120 to 277 in the USA, 120 to 347 in Canada, etc) and possibly even frequency range (50 to 60 Hz or maybe even to 400 Hz). Then the voltage can change, possibly even while running.

AFAIK, electronic ballasts of recent manufacture do not have a memory. If you want to be sure, contact the ballast manufacturer and ask.

I asked this question of Advance ballasts about 3 or 4 years ago on a job I had. The building would have 277 volt lighting circuits, but our temporary power was only 120 volts. Used the temporary to run some of the lights, everything worked fine when 277 was finally available.

I would tend to agree with John, here.
If the manufacturer doesn't know, no-one does.

In these days of multi-voltage equipment (ie: made to run all over the world), you'd think that this sort of thing would be reasonably happy with any within say 100-300VAC, I could be way wrong though.

John: (Redsy)
What brand ballast and what spec? 2 lamp T8? etc?

I have a contact at a few mfg. if you want help

I cannot imagine any purpose for a multi-voltage ballast to be made in such a way that it can accept any voltage in the specified range or list when first used, but not do so afterwards. If it has the circuitry that can operate on any voltage, it would seem to me that it would be more complicated to make it remember that and intentionally malfunction when a different voltage it has the capability to handle is later used. If such a beast exists, I would sure like to get hold of one (to take apart and see what they are doing).

OK, I can see one purpose ... to destroy the market for used ballasts.

I agree. "Wide mouth" power supplies are common in the computer biz as soon as you get away from market driven (cheap) PCs. They can take anything from 100-250v 50-60 hz. There is no reason electronic ballasts can't do the same thing.

Thanks everyone!
I spoke to the manufacturer and was told they can indeed be re-connected.

I was concerned because I was once told that multivoltage photocells (the twist-lok style that screw onto HID fixtures) can not be used on a different voltage once they are installed initially on a certain voltage.