Actually this should be pretty easy and should be just as easy as switching one wire.

Most ballasts have multiple input voltages and then use a "common" ground.

As a rough diagram look below:

-----120v
-----240v To Bulb ------
-----480v To Bulb ------
-----Ground


Each set of dashes is a lead coming out of the fixture. Right now, the wires going into the left side are hooked up to 240v and ground, all you have to do is move the 240v wire to the 120v wire and your all set.

This will tell the ballast to draw more current (Amps) from your electrical system to produce the same amount of power (Watts) to power the bulb.

Good news: Net effect to your electric bill will be 0

A step-up transformer at 400 or 600 Watts will not be cheep, this is much easier and probably only involves moving a wire nut.
ddxsinxcosxdx Reviewed by ddxsinxcosxdx on . rewire 120 240 ballast does anyone know the basics to rewiring a ballast? It was originally at 120v but then was switched to 240v, how would one switch it back? A friend called me asking this ? this morning, im no Electrition so i told them to wait a day or 2 for my response. thanks for the help Rating: 5