Do-It-Yourself Repairs & Basic Wiring Projects:
How Do I ....
Convert 220 Volts to 110 Volts

By Terry Peterman, the Internet Electrician

Q:  I would like to know if I can convert 220 volts to 110 volts without using a step down transformer?

A:  Short answer is: "yes", you can do this without a step down transformer.

To give you a specific answer I would have to know the exact application and the specific situation.  However, the most common example would be replacing an electric range or dryer to a natural gas unit that now only requires 120V power.

In this example, you have some choices.

Option One
You can purchase an adapter plug that inserts in to the existing 125/250V outlet and converts it to a 15A 120V regular outlet complete with overload protection in the form of a pop-up breaker, or a simple fuse.

Option Two
Another option is to remove the existing 30 or 50A, 125/250V receptacle from the outlet box (turn off the breaker of course). 

• Run a 2-wire cable to a new outlet box where you would install a new 15A 125V receptacle. 

• In the existing outlet box you would splice your bare ground wires together, splice the white wires together, and the black wire from the new 2-wire to one of the existing hot wires (red or black). 

• Tape off or cap off the other unused hot wire with a wire nut. 

• Install a blank cover plate on the existing range or dryer outlet box. 

• In the main service panel, shut off the main breaker (after arranging for an alternate light source of course), remove the existing 2-pole larger amperage breaker, and install a single pole 15A breaker in it's place. 

• Use a panel filler insert to plug the vacant hole in the panel cover.  You would then cap off the unused hot wire with a wire nut or tape, and connect the other hot wire to the new 15A single pole breaker. 

It is very important to consider the amperage as well as the voltage of any receptacle or connected equipment before making any changes.  You can use larger wire than what is required for a circuit (i.e. 15A breaker feeding #8 AWG wire) but never a larger breaker than the rating of the wire (i.e. 50A breaker feeding #14 gauge wire).

- Terry Peterman, the Internet Electrician