Lochinvar & A.O. Smith 100208551 Temperature Sensor

The Lochinvar & A.O. Smith 100208551 Temperature Sensor is a critical OEM replacement component designed for high-accuracy thermal monitoring in commercial and residential hydronic systems. This NTC thermistor probe provides essential data to the Smart System control module, ensuring precise modulation of the burner and pump logic based on real-time fluid temperatures. As a direct 100208551 replacement part, it is functionally identical to the Lochinvar TST2313 and TST2313K sensor models. Featuring an 11-3/4 inch lead length and a 3/8 inch diameter element, this immersion temperature sensor is engineered for rapid thermal response and long-term stability in high-demand environments like the Lochinvar Knight boiler, Copper-Fin II, and EnergyRite pool heaters.

When a system presents a Sensor 1 Open or Sensor 1 Shorted fault code, replacing the 100208551 HVAC sensor is the standard protocol to restore safe operation. This genuine A.O. Smith sensor helps maintain the correct temperature resistance curve required for efficient combustion and domestic hot water (DHW) priority. By installing a Lochinvar OEM part, technicians ensure the sensor element matches the control board's programmed parameters, preventing ghost faults and inaccurate high-limit tripping that can occur with generic universal thermistors.

Key Benefits

• Direct OEM Compatibility: Specifically calibrated for Lochinvar Knight (KBN, KBP) and Copper-Fin II (CH, CF, CS) models to ensure seamless control integration.
• Precision Thermal Sensing: High-sensitivity NTC element delivers accurate resistance signals to the boiler control module for fuel-efficient modulation.
• Rugged Build Quality: Designed with a 1-3/4 inch stainless steel probe and high-temp lead wires to withstand constant immersion and cycling.
• Verified Cross-Reference: Confirmed as the current replacement for legacy part numbers TST2313 and TST2313K.

Common Questions

How do I test if the 100208551 sensor is defective?
Using a multimeter set to the Ohms scale, measure the resistance across the sensor leads. Compare your reading against the Lochinvar sensor resistance chart for the current ambient temperature; an "OL" reading indicates an open circuit, while 0 Ohms indicates a short.

Can this sensor be used for both inlet and outlet water temperatures?
Yes, in many Copper-Fin II and EnergyRite applications, this specific 10k or 12k ohm-style immersion probe is utilized for both the inlet and outlet headers to monitor the temperature delta across the heat exchanger.

What causes these sensors to fail prematurely?
Common failure points include moisture intrusion into the thermistor potting, wire fatigue at the probe junction, or excessive scale buildup on the sensing element which insulates the probe and causes delayed temperature readings.

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.