I have a Fetco CBS-52H-15 machine. It is 240v but I'm wondering if it can be reduced to 120v? If so, how do you wire it that way? Do you need to configure anything on the machine too?

It cannot run on 120V.

Ok. It's 3 phase right now. Can it be changed to single phase?

There are ways to convert 3 phase to single phase, but it would likely cost more than just getting another brewer. They are cheap on CL. I just bought a CBS-2052 in great shape for $400. I bought a CBS-61H last year with 4 Luxus dispensers for $400.

Thanks for the input thus far. Do you know if my machine is a single phase or 3 phase?
I have a 3 prongs twist lock outlet 240v 20amps.
I want to plug this machine into it to avoid running new electrical for it if I can.

Three phase power would have a L1, L2, and L3 connection, with a neutral conductor for 4 wire or without for a 3 wire connection. Since you only have an L1 and L2 in the photo provided it looks like you have a standard 240 V connection and don't need a three phase hookup.

The voltage measured between L1 and L2 will be 240 and the voltage between either of the lines and neutral will be 120 V.

Since you only have a three prong outlet, I'm not sure what's missing, a neutral or ground connection. Can you type out the numbers on the outlet? You may want to have an electrician involved in making the connection if you're uncertain.

Looks like the White wire is capped off.

I would probably put in a 4 wire receptacle and plug so that you have L1, L2, the neutral and ground going to the Fetco.

Problem is I have another machine that plugs into this that is 3 prong only. If I changed to a 4 prong receptacle, could I put a 4 prong plug on the 3 prong plug?

I'll defer that to a qualified electrician.