Just registered tonight & this is my first post so bear with me. I just got called out by a new customer wanting me to try to repair her Cantherm Geo system M#DUO520.This system uses one additional air handler with a hot water coil for heating. Seperate t- stats for both. Relay panel mounted on wall for system control. oh yeah also used to heat domestic hot water for home. On a call for heat the seperate air handler won't bring on geo unit. Believe me this is a cobbled up mess, disconnected wires hanging everywhere & home owner doesn't know why. And of course no unit literature or wiring skematics are available. Wondering if anyone can help locate info on this system. Looking at replacement just trying to buy some time.