Description
The Weil McLain 389-900-229 is a Universal 3-In-1 Temperature Sensor engineered for maximum flexibility in hydronic heating system installations. Designed to serve three distinct sensing roles in a single unit, this sensor eliminates the need to stock multiple sensor types and simplifies service calls across a wide range of Weil McLain boiler applications.
Three Sensing Modes in One
- Outdoor sensor — monitors ambient outdoor temperature for outdoor reset and weather-responsive control strategies
- Indoor strap-on sensor — clamps directly onto piping to measure supply or return water temperatures without system penetration
- Well sensor — inserts into an immersion well for direct fluid temperature measurement in hydronic loops
Key Features
- Universal design compatible with a broad range of Weil McLain boiler control systems
- Single sensor replaces three separate sensor SKUs, reducing inventory and installation complexity
- Durable construction suited for demanding residential and light commercial hydronic environments
- Reliable temperature sensing supports accurate boiler modulation and energy-efficient operation
- Genuine Weil McLain OEM replacement part for assured fit and performance
Applications
- Outdoor reset control systems
- Hydronic supply and return temperature monitoring
- Boiler aquastat and control module integration
- Residential and light commercial hot water heating systems
Product Details
- Brand: Weil McLain
- SKU / Part Number: 389-900-229
- Sensor Type: Universal 3-In-1 (Outdoor / Indoor Strap-On / Well)







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