WE just had installed a Carrier GT-PX geothermal unit and had it hooked up to our hot water heater (HWH). Just found out, that this is the first unit our contractor has installed in a residence versus his commerical installations. Found problems with his installation and are questioning whether the HWH is hooked up properly. For starters, the contrator did not turn on the hot water generator system until we questioned him as he didn't know the unit came with it turned off. My husband just got his hands on the manual and found the contrator had hooked up the lines backwards from the geothermal unit to our HWH! The contrator came out and routed them properly. So my question is, how can we tell if the unit is acutally heating up our water in the HWH? My husband is an electrician and can access the unit. So what are the signs that will tell us that the geothermal unit is actually heating our water in the HWH which sits just beside the unit. Thanks for any help you can give me.