Description
The Xylem-McDonnell & Miller 51-S-2-HD is a mechanical combination water feeder and low water cutoff designed for reliable protection and automatic water makeup on low pressure steam and hot water boilers. This listing covers the snap-acting SPDT switch head mechanism only (Part Number 136200), making it an ideal replacement component for existing 51-S-2-HD installations.
Product Overview
The 51-S-2-HD combines two critical boiler safety and maintenance functions in a single, proven mechanical design. The low water cutoff monitors boiler water level and interrupts the burner circuit when water drops below a safe operating threshold, while the automatic water feeder replenishes the system to maintain proper water levels — reducing manual maintenance and protecting against dry-fire damage.
Key Features
- Combination mechanical water feeder and low water cutoff in one unit
- Suitable for low pressure steam and hot water boiler applications
- 35 PSI maximum vessel pressure rating
- Snap-acting SPDT (Single-Pole Double-Throw) switch for reliable electrical switching
- Head mechanism only (Part Number 136200) — ideal for replacement or service
- Trusted McDonnell & Miller design for long-term boiler protection
Specifications
- SKU: 51-S-2-HD
- Part Number: 136200
- Max Vessel Pressure: 35 PSI
- Switch Type: Snap-Acting SPDT
- Application: Low Pressure Steam and Hot Water Boilers
- Component: Switch Head Mechanism Only
Application
The 51-S-2-HD head mechanism is engineered for use on residential and light commercial boilers where dependable low water protection and automatic water makeup are essential. The snap-acting SPDT switch ensures positive, reliable burner circuit interruption when water levels fall below safe limits, helping to prevent costly boiler damage and extend equipment life.
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