yep- that's me with the 250 v /20 amp outlet. I wired my stage with 125 v 20 amp and 15 amp outlets. I have a big ac/heater I want to put in and bought the single 250v/20 amp outlet from home depot, but unlike the 125 v outlets, it doesn't have clear color coded slots. The outlet has a ground screw (green) but it has 2 brass screws as opposed to the 1 silver used for the white wire, and the 1 brass screw used for the black wire. One the 125 outlets the black wire goes to the breaker, and the ground and white wire goes to the thing inside the breaker box with holes for the ground and white wire alternatly- I'm stuck on what to do with the 250v wires.

 

In order to get 240 volts to a receptacle it requires 2 hot legs of 120 volts feed from a double pole breaker.

As long as your AC and heat unit does not need a neutral, you could use 2 wire cable + ground and re-identify the white as a color other than white or green. A magic marker works well for this, or color coded electrical tape.

At the receptacle and breaker it does not matter which insulated wire connects to which screw.

 

You should have three wires: black, white and bare. If you have four (black, red, white, and bare), then you have one more than you need.

It would be helpful if you would tell us exactly which receptacle you have. It would also be helpful if you would tell us exactly what cable you used, and exactly what breaker you used. Without these critical pieces of information, we have to guess a bit.

The two hot poles on a 240-volt recepacle are interchangeable. One is for each of the two wires you connected to the 240-volt breaker (either black and white, or black and red). If you used a black/red/white/bare cable, and if there are only three screws on the receptacle (two brass and one green), then you should not attach the white wire to anything at the receptacle end.

If you give us more information, we can be more helpful.