Lochinvar & A.O. Smith 100208549 Sensor

The Lochinvar & A.O. Smith 100208549 Inlet Water Sensor is a critical genuine OEM replacement part engineered for high-precision temperature monitoring in commercial and residential hydronic heating systems. This immersion-style K-type sensor provides real-time data to the integrated control board, allowing the system to modulate firing rates and maintain target setpoints based on incoming water temperatures. Designed as a direct drop-in for the TST2060 and TST2060K, this NTC thermistor sensor ensures the control logic receives accurate resistance signals to prevent short-cycling and optimize thermal efficiency in Lochinvar Knight and A.O. Smith boilers.

For service technicians, verify the 100208549 sensor resistance against the manufacturer’s temperature-to-resistance chart during troubleshooting. A drifting or failed inlet water sensor often manifests as erratic modulation or system lockout codes. This factory-new OEM temperature probe features a durable 1/4" NPT or immersion housing—depending on specific manifold configuration—to withstand the constant thermal cycling of high-efficiency gas-fired units. By replacing aged sensors with authentic Lochinvar boiler parts, contractors ensure the outdoor reset curve and internal safety limits function within factory tolerances.

• Precision Thermal Monitoring: Provides the boiler control board with exact inlet water temperature data to maximize energy savings.
• OEM Compatibility: Guaranteed fit for Lochinvar and A.O. Smith units, including 400-801 series and WB-series boilers.
• Interchangeable Design: Fully replaces legacy part numbers TST2060, TST2060K, and 100170596.
• System Reliability: Genuine OEM construction prevents signal noise and premature failure common in aftermarket thermistors.

How do I test if the Lochinvar 100208549 sensor is faulty?
Use a multimeter to check the resistance (ohms) across the sensor terminals. Compare your reading to the temperature-to-resistance table found in the boiler’s service manual. If the sensor is open, shorted, or significantly out of range for the current water temperature, it requires replacement.

Can this sensor be used as an outlet or flue sensor?
While some sensors share similar thermistor curves, the 100208549 is specifically calibrated and physically designed for inlet water temperature monitoring. Always match the specific OEM part number to the application to ensure safe and accurate modulation.

What are the symptoms of a failing inlet sensor?
Common indicators include the boiler failing to modulate correctly, "Sensor Open" or "Sensor Short" error codes on the display, or the system failing to reach the calculated outdoor reset setpoint.

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.