Heat Exchange Thermistor

Rheem RTG20212BC Thermistor – OEM Sensor for Heat Exchanger Temperature Monitoring

The Rheem RTG20212BC is a factory-specified heat exchanger thermistor designed for use in Rheem tankless gas water heaters. This thermistor monitors the internal temperature of the primary heat exchanger and transmits real-time data to the unit’s control board. The control system uses this input to manage burner modulation and ensure safe operation within temperature design limits.

Component Function

This NTC thermistor is located in close proximity to the heat exchanger and plays a critical role in maintaining thermal balance within the combustion system. It supports multiple control functions, including high-limit protection, energy-efficient burner cycling, and diagnostic feedback in overheat or scale-related conditions.

Technical Specifications

• Part Number: RTG20212BC
• Sensor Type: NTC thermistor (negative temperature coefficient)
• Function: Heat exchanger temperature monitoring
• Application: Select Rheem tankless gas water heater models
• Connection: Plug-in wire harness to main control board
• Location: Heat exchanger sensor mount (model-specific position)

Installation Considerations

Installation requires full power isolation and system shutdown. The RTG20212BC should be mounted using the original securing hardware and properly routed to avoid contact with high-temperature surfaces. Verify electrical continuity and correct orientation upon connection. Sensor readings should be checked during system diagnostics to confirm proper integration. All work should be performed by qualified HVAC or plumbing technicians to maintain safety and code compliance.

Field Applications

This component is typically replaced in response to error codes related to exchanger temperature faults or operational irregularities such as burner lockout or short cycling. It is also used during routine service for systems showing signs of thermal performance degradation due to fouling, scale, or airflow restriction. OEM thermistor replacement ensures control board compatibility and proper system calibration.