Lochinvar & A.O. Smith 100208561 Flue Sensor

The Lochinvar & A.O. Smith 100208561 Flue Sensor is a critical high-temperature monitoring component engineered for precision in FTXL FTX 400 - 850(N/L) heating boilers and Aquas AP400 - 850 commercial pool package heaters. As a direct replacement for TST20026K and 100170554, this updated flue temperature sensor provides real-time thermal feedback to the control board to verify safe combustion levels and prevent exhaust system overheating. For a technician in the field, this HVAC temperature sensor is essential for diagnosing flue gas temperature spikes that could indicate heat exchanger fouling or improper air-fuel ratios. Installing this genuine OEM boiler part ensures the system maintains optimal thermal efficiency while adhering to factory safety parameters, minimizing equipment downtime and preventing premature component failure in demanding commercial hydronic applications.

Key Benefits

• Direct OEM Compatibility: Specifically designed to replace obsolete TST20026K and 100170554 sensors in Lochinvar FTXL and A.O. Smith commercial units.
• Precision Monitoring: Delivers accurate flue gas temperature readings to protect the PVC or CPVC venting from thermal damage.
• Enhanced System Safety: Triggers immediate safety shutdowns if stack flue temperatures exceed the programmed threshold, protecting the heat exchanger.
• Rugged Build Quality: Built to withstand the corrosive environment of high-efficiency condensing boiler exhaust streams.

Common Questions

Is this sensor compatible with older TST20026 models?
Yes, the 100208561 is the official updated version intended to replace TST20026K, TST20026, and 100170554 across all compatible FTXL and Aquas series boilers.

What are the symptoms of a failing flue sensor?
Common indicators include intermittent "flue temp" lockout codes, inconsistent blower modulation, or the control board failing to recognize the exhaust temperature during the ignition sequence.

Does this part require professional calibration?
While the sensor provides a standard resistance signal, it must be installed by a licensed contractor to ensure the unit is safety-tested and that the flue gas analysis matches the control board's output.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.