Description
The Xylem-McDonnell & Miller 51-2-HD (Part Number 135100) is a reliable mechanical water feeder and low water cut off engineered for low pressure steam and hot water boiler applications. This listing covers the snap-acting SPDT switch head mechanism only, making it an ideal replacement component for existing 51-2-HD installations.
Product Overview
Designed to protect boilers from dangerous low-water conditions, the 51-2-HD automatically feeds water to maintain safe operating levels while simultaneously cutting off the burner if water drops below the minimum safe threshold. The snap-acting SPDT (Single Pole Double Throw) switch head delivers fast, decisive switching action for dependable boiler protection.
Key Features
- Dual-function design: mechanical water feeder and low water cut off in one unit
- Snap-acting SPDT switch head mechanism for fast, reliable switching response
- 35 PSI maximum vessel pressure rating for low pressure steam and hot water boilers
- Head mechanism only — designed as a direct replacement for existing 51-2-HD assemblies
- Trusted McDonnell & Miller engineering backed by Xylem’s global expertise
- Compatible with low pressure steam and hot water boiler systems
Specifications
- Part Number: 135100
- Model: 51-2-HD
- Maximum Vessel Pressure: 35 PSI
- Switch Type: Snap-Acting SPDT (Single Pole Double Throw)
- Application: Low Pressure Steam and Hot Water Boilers
- Component: Switch Head Mechanism Only
Application
The 51-2-HD head mechanism is suited for residential and light commercial boiler systems requiring dependable low-water protection and automatic water feeding. Its snap-acting SPDT switch ensures the burner is cut off promptly when water levels fall below safe limits, helping prevent costly boiler damage and unsafe operating conditions.
