Description
The Xylem-McDonnell & Miller 159S is a combination low water cut-off and pump controller engineered to provide reliable boiler protection and automatic pump management in a single, compact unit. Designed for use on steam boilers, the 159S monitors water level continuously and interrupts the burner circuit whenever the water drops to an unsafe level, helping prevent costly boiler damage and potential hazards. Simultaneously, its integrated pump controller function automates feedwater pump operation to maintain proper water levels at all times.
Key Features
- Combination low water cut-off and pump controller in one unit — reduces installation time and hardware costs
- Two snap-acting SPST switches provide independent control of the burner circuit and the pump circuit
- Float-operated mechanism responds quickly to falling water levels for fast, reliable protection
- Designed for steam boiler applications requiring automatic feedwater pump control
- Durable cast iron body construction for long service life in demanding boiler room environments
- McDonnell & Miller’s proven low water cut-off technology trusted by HVAC professionals for decades
- Part Number: 178802
How It Works
The 159S uses a float mechanism to continuously sense the water level inside the boiler. As water drops to the pump-on set point, the pump controller switch activates the feedwater pump to restore proper water level. Should the water level continue to fall to the low water cut-off set point, the second SPST switch opens the burner circuit, shutting down the boiler to prevent a dangerous dry-fire condition. When water is restored to a safe level, the unit automatically resets and allows normal boiler operation to resume.
Ideal Applications
- Steam heating boilers in residential, commercial, and light industrial settings
- Systems requiring automatic feedwater pump control with integrated low water protection
- Retrofit or replacement of aging low water cut-off devices on existing boiler installations
Product Specifications
- Brand: Xylem-McDonnell & Miller
- Model: 159S
- Part Number: 178802
- Switch Type: Two Snap-Acting SPST Switches
- Function: Combination Low Water Cut-Off and Pump Controller
- Application: Steam Boilers
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