What exactly are you wanting to know? How to actually make the connection?
If so, what is the voltage and amperage of the air compressor?
What is the brand and model number of the genset?
On the 4 poles of the genset, you are correct. 2 poles are hot (black and red), one is neutral (white) and the other is ground (green).
You do need both hots to get 230, but they can not be connected together. The 2 line connectors on the switch is where they go.
If your compressor only has 3 wires, you will not use the ground wire. You will only have 2 hots and a neutral.
What is the brand and model number of the compressor, so I can try to find a schematic? Is there a schematic on the switch cover?
Is there any chance you could get a picture of the compressor switch box and post it here?
Is the compressor 120V or 240V?
Changing the voltage on the motor requires moving several wires in the motor itself.
I will be unable to help without the schematic or instructions, so we can determine which voltage it is currently wired for.
I will opt out of this question so another expert may help you.
From what you are describing, yes, that is the way it should be wired.
But I have never seen a neutral go to ground before. I have to wonder whether there is a wire missing. The schematic would show this.
Unless what you are calling a ground screw is actually a neutral lug. If so, this lug will be insulated from ground.
I do not have this particular schematic, and have a call in to CH.
I am waiting to hear from them.