Electrical help please
 

Ok, I've got a 220v compressor that I'm trying to hook up. At the pressure switch I have a black,white, and green wires. The plug at the wall is a 4 prong 30amp which I believe is a 10-4 with black,red,white,and green. How would I go about hooking it up?

Plug

looking at your receptacle (picture)the vertical left and vertical right are your "hot" connections in your case white and black.
the angle shaped connector at the bottom is a Neutral (which you compressor does not have)and the top is a ground (green)
In my state the neutral and ground are one in the same ,but you need to check how your state(service panel) is set up. If in doubt call an electrician
Remember 110 volts will get your attention 220 will KILL YOU

That appears to be a 14-30R 3 phase 30 amp receptacle. Just be sure that it is 220V-240V three phase. Since your compressor is single phase you'll just need to connect it to one of the three phases. Refer to diagram/wire colors and wire them to the 14-30P ("P" for Plug) as shown on the right side of the diagram.

You won't have 3 phase in a residential house. The outlet is a 220 single phase with a neutral and a ground. The top is the ground and the bottom is the Neutral. You can hook up your compressor motor by the diagram MLL provided Just make sure the motor is wired for 220v and not 110. Some motors can be wired for either voltage.

white to white, black to black, green to green

Thanks 😀

Well the OP didn't state where he was hooking this up; i.e. home, work, someones shop, etc. HE DID however state that there are white, black, red, and green wires which can indicate 3 phase wire (I wire three phase often).
Regardless, if it IS in a home VERY unlikely it is 3 phase but the normal household 240/250V 2 phase service (2 phases 180deg. out so they add together). If you refer to the diagram below you'll see how a 14-30R would be wired in a home 2 phase setting.

Between Y (Hot) and W (Neut.) you have 120/125V
Between X (Hot) and W (Neut) you have the other 120/125V 180 degree out.
Between Y (Hot) and X (Hot) you have 240/250V

So whether it is 3 phase industrial or 2 phase household service, the diagram above (post #4) shows how to properly wire a 14-30 plug to mate with his 14-30 receptacle for his application. (NOT NECESSARILY white to white, black to black BTW as in this case).