Weil McLain 383-500-125 Sensor

The Weil McLain 383-500-125 Outdoor Temp Sensor is a critical OEM component designed to provide real-time ambient temperature data to the Weil McLain Ultra Gas Boiler control module. By utilizing a 12k ohm thermistor encapsulated in a weather-resistant housing, this outdoor reset sensor allows the boiler to dynamically adjust its firing rate and supply water temperature based on external conditions. This process, known as outdoor reset logic, significantly increases system efficiency by preventing short-cycling and maintaining optimal condensing temperatures within the heat exchanger. For a proper install, contractors should mount the 383-500-125 on the north side of the structure, at least 10 feet above grade, to avoid false readings from direct sunlight or mechanical exhaust. This replacement boiler sensor is compatible with the full range of Ultra series units and is essential for restoring high-efficiency performance after a sensor fault or open-circuit error. Integrating this HVAC outdoor sensor ensures the control board can calculate the correct reset ratio for various heating loads.

• Ensures accurate outdoor reset control for maximum fuel savings and thermal comfort.
• Designed for direct compatibility with Weil McLain Ultra Gas Boilers and advanced control boards.
• Ruggedized housing protects the 12k ohm thermistor from moisture and environmental degradation.
• Reduces wear on the ignition system and heat exchanger by optimizing cycle times.
• Facilitates precise temperature regulation across a wide ambient range of -40°F to 140°F.

• Where is the best location to mount the 383-500-125? It should be installed on an outside North-facing wall to prevent solar gain from skewing the temperature data. Avoid placement near dryer vents, doors, or windows.
• How can I verify if the sensor is defective? Technicians should use a multimeter to check the resistance across the sensor leads. At 77°F (25°C), the sensor should read approximately 10,000 to 12,000 ohms; significantly higher or lower readings typically indicate a failed component or wiring issue.
• Does this sensor come with the mounting hardware? The unit includes the sensor and the integrated mounting enclosure required for a standard exterior installation.

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.