Thru Wall Air Conditioner (Electrical question)

This is for the electrical experts.
I have a unit that requires a new air conditioner. It is a thru the wall unit, which is basically a window type air conditioner. The outlet is currently wired for 220. However, most new units I am looking at are 110 (and cheaper). Is it practical/safe to use a step down transformer to run a new A/C unit on the 220 line?

Thanks for the advice.


Have an electrician take a look.

Normally, where I am, I got three phase power that’s delivered to the home, i.e. two hot lines: A, B, plus a neutral. For the 220 volt equipment, you got two hots lines A, B, plus the neutral going into a special three prong outlet. The higher voltage of 220v exists between lines A and B, and 110v between A to neutral, or B to neutral.

For 120 volts, it’s simply line A (or B) to neutral. Changing voltage would involve keeping line A at the outlet, with the neutral.

I had the 208 volts (it’s 208 in NYC) changed to 120 volts at one unit, and 120 volts changed to 208 volts, at my house, as the higher voltage runs at greater efficiency. Both changes involved rewiring, no transformers involved.

In one of the 220v to 110v conversions, we simply installed a new 110v outlet next to the 220v, running one hot, and the neutral lines over. It’s a dedicated circuit for AC, tenants can plug into either 220v outlet or the 110v right next to it…

as frank stated modifying a 220v service to provide 110v is not terribly difficult so i would avoid the ‘step down’ transformer route.

i know that very often getting small, low tonnage a/c units in 220v is sometimes a little hard and when you find them they may be a little more expensive but you should check the price the electrician will give you against the amount you intend to save by buying a 110v a/c unit. if the 220v a/c is 30-50.00 more but the electrician wants to charge you 50-100.00 for the service call you might be better just buying the more expensive a/c unit

good luck!