Lochinvar & A.O. Smith 100208544 Outlet Sensor

The Lochinvar & A.O. Smith 100208544 Hi-Limit Outlet Sensor is a critical genuine OEM temperature sensor engineered for precise thermal monitoring in high-efficiency condensing water heaters and boilers. This NTC thermistor provides real-time outlet water temperature data to the SMART SYSTEM control module, ensuring the unit operates within safe parameters and providing essential high-limit protection against localized overheating. Designed as a direct replacement for obsolete part numbers TST20009, TST20009K, and 100170537, this sensor maintains the factory-calibrated resistance-to-temperature curve required for accurate Delta T monitoring and lockout prevention.

Built for the rigorous environments of hydronic heating systems, this sensor is a standard component in Lochinvar Knight, Knight XL, and Armor series units. It features a high-reliability plug-and-play connection to minimize intermittent resistive imbalance—a common cause of nuisance Lockout-Failure codes. By accurately sensing the heat exchanger's discharge temperature, the 100208544 outlet sensor allows the control board to modulate firing rates and pump speeds effectively, protecting the stainless steel heat exchanger from thermal stress and scale buildup.

Key Benefits for Technicians:

• Genuine OEM Reliability: Eliminates compatibility issues associated with universal aftermarket sensors that may drift.
• Precise High-Limit Protection: Prevents Outlet Temp Shutdown by providing accurate data for safety limit thresholds.
• Broad Compatibility: Fits a wide range of models, including Knight XL KB81 to KB286 and Armor 151 thru 801.
• Direct Replacement: Seamlessly replaces TST20009 and TST20009K without requiring harness modifications.
• System Efficiency: Enables optimal modulation and condensing operation by providing stable temperature feedback.

Common Questions Regarding 100208544:

• What causes an "Outlet Sensor Fault" on Lochinvar boilers? This often occurs if the internal thermistor develops an open circuit or if the resistance values drift outside of the 10k-ohm (at 77°F) nominal range.
• Can I use a system sensor in place of this outlet sensor? No, while they look similar, the 100208544 is calibrated for specific high-limit safety functions and must match the control board's programmed NTC profile.
• Does this include the replacement O-ring? This genuine OEM sensor is typically supplied as the individual sensing element; confirm if your specific application requires a new well or gasket separately.

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.