Hello,

I have a subpanel directly under my main breaker on the meter pole. This subpanel was used for a 8 x 12 shed. that was set up with a small a/c, light, and about 6 outlets. the wire running from the subpanel to the breaker box inside the shed was a 10/3 and has four wires.  I no longer have the shed. I want to run this to a 20A-250v outlet for an A/C -heater window unit. But the outlet only has three screws.

I was told to combine the red and black together and use on one screw. then the white to other top screw and ground to ground.  Will this work?

Please help.

Thank you

Sharon