For the control side, you just send the Home Management System a 0-10V signal, and that is it.? (0V=Off, 5V=50%, 10V=100%)
They should be doing everything else.? There shouldn't be anything else connected to the Crestron equipment.
All of the heaters that are compatible with the Home Management System are 240V.? So, it sounds like they have something wired incorrectly.
It's worth noting that the little 120V heaters (Infratech only makes a couple) are not compatible with the Home Management System.
I'm not sure what relay you're referencing in the Infratech panel.? RGC1P48V42ED???
This is what controls one leg of the 240V line to the heaters.
It should be connected to the Crestron 0-10V through the built-in connection block.
Also, there should be a 24VDC input from the built-in AC/DC power supply.? This supplies power to the RGC1P module.
Finally, there the in and out for one of the 240V heater legs.
Good luck,
Brian