to convert from the 240v to 120 volt you will have to change the breaker. most states will require you to call an electrician to do this sort of work. it is easy enough to do just requires popping off the cover popping out the breaker and replacing it with a 120 volt breaker.

theres 3 wires that come into your main panel, 2 hot wires and 1 neutral wire. the 2 hot wires will equal 240 volt and by using the neutral you split that giving you 120. you cant simply replace the plug as the 2 wires you have coming into the plug will be off both the A and B phase. to convert to 120 volt you need to have either the A or the B phase running on the hot wire (black wire) from your panel to your plug, then your grounding conductor (white wire) hooking into the neutral wire in your panel.

this post is strictly informational, i accept no responsibility for any accidents, fires, electrical shocks or burns from anyone attempting this themselves. when in doubt call a professional, no sence burning your house down trying to save a few nickels. there is a differance between wiring something, and wiring it right. if you dont have the knowledge, and degree in your hand, you should not attempt this. once again, call a professional, it would be all of a half hour job.
Frickr Reviewed by Frickr on . How should I convert 220 volt to 110? After many delays, we're finally making progress on our new grow room. The framing is just about done and soon we'll be ready to wire it. We have an un-used 220 volt outlet next to the new room. We'd like to convert this to two seperate 110 volt outlets so we can run the window Air Conditioner on one and lighting/fans on the other. A quick search on-line showed that we can either have it re-wired into two 110 circuits or buy an adapter. Durn if we can't find the adapter. Everything Rating: 5