Description
Xylem-McDonnell & Miller 63-B Mechanical Low Water Cut Off
The Xylem-McDonnell & Miller 63-B is a reliable, auto reset mechanical low water cut off (LWCO) designed to protect hot water and steam boilers from the dangers of low water conditions. With a 1″ NPT connection and a maximum boiler pressure rating of 50 PSI, this unit delivers dependable, code-compliant protection for residential and light commercial boiler systems. The included float block assembly ensures accurate water level sensing and consistent automatic reset operation — eliminating the need for manual intervention after a low water event is resolved.
Key Features
- Auto reset operation — automatically resets once proper water level is restored
- 1″ NPT pipe connection for straightforward installation
- 50 PSI maximum boiler pressure rating
- Compatible with both hot water and steam boiler systems
- Includes float block assembly for accurate water level detection
- Mechanical design for proven, long-term reliability
- Part Number: 142700
Product Specifications
- Brand: Xylem-McDonnell & Miller
- Model / SKU: 63-B
- Part Number: 142700
- Connection Size: 1″ NPT
- Maximum Boiler Pressure: 50 PSI
- Reset Type: Automatic (Auto Reset)
- Application: Hot Water and Steam Boilers
- Includes: Float Block
Why Choose the McDonnell & Miller 63-B?
McDonnell & Miller has been a trusted name in boiler safety controls for over a century. The 63-B continues that legacy with a rugged mechanical design that safeguards your boiler investment and prevents costly damage caused by low water conditions. Its auto reset functionality minimizes downtime and service calls, making it an ideal choice for installers and building owners alike.







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