Originally Posted by brewhokie
Sorry bonehead mistake...Heating element wouldn't work very well on an open circuit. This is what I get for dreaming of an e-brew rig while trying to do work.
You would need to switch one side of your element from one of the 120 legs to neutral. That would move it from 240V to 120V. That would work fine.
Unfortunately, SSRs I've used are SPST. Mechanical relays are usually SPDT, which what you want. This would work fine if you're not switching a lot.
BTW, you might have trouble with 4500W in the RIMS. Might boil on you.
The other posts are right, though, you really just need a controller to PWM the power through an SSR to get the average power you're looking for.