A patented feature in the RHQA-12 and higher models that stages supplemental heat. It limits the KW input to only what is necessary for the current demand, preventing energy waste.

Since the RHQA 1220T is a legacy model (often dating back to the late 1980s or 1990s), regular maintenance is critical. Rheem RHQA 2020T Heat Not Working? Expert ... - JustAnswer

Designed with two removable panels on the front and sides for easy access to the blower motor , sheaves, and filters. Common Maintenance & Troubleshooting