• Apr 29, 2026 Rheem Rhc Tst550cmms Wiring ** Often caused by blown fuses, tripped breakers, or loose line voltage connections. **Thermostat Not Communicating:** Could stem from incorrect wiring between R, W, or C terminals or a defective thermostat. **Relay Failures:** Faulty relay output wiring might prevent heaters f By Maudie Kohler
