Description
Xylem-McDonnell & Miller 42S-HD — Combination Low Water Cut Off and Pump Controller
The Xylem-McDonnell & Miller 42S-HD is a combination low water cut off and pump controller engineered specifically for steam boiler applications. Supplied as the head mechanism only, this unit is designed for straightforward replacement or upgrade of an existing float-type control body without the need to drain the system or disturb boiler piping. McDonnell & Miller’s trusted float-operated design has protected steam boilers in residential, commercial, and light industrial settings for decades, and the 42S-HD continues that legacy with reliable, code-compliant performance.
Key Features
- Combination low water cut off and pump controller in a single, compact head mechanism
- SPST snap action switches provide positive, reliable switching for both burner cut off and pump control functions
- Head mechanism only — mounts directly to compatible McDonnell & Miller float bowl assemblies for fast, cost-effective replacement
- Designed specifically for steam boiler service, protecting against dangerous low-water conditions
- Float-operated control for accurate, consistent water level sensing
- Durable construction built to withstand the demanding thermal and pressure environment of steam boiler rooms
- Trusted Xylem-McDonnell & Miller engineering with a long track record in the HVAC and hydronic industry
Application
The 42S-HD is ideal for replacement or service work on steam boilers where the existing head mechanism has failed or requires upgrading. By supplying only the head mechanism, installation is simplified — technicians can swap the control without draining the boiler or replacing the entire assembly. The SPST snap action switches deliver clean, decisive switching action to cut burner operation when water drops below the safe operating level and to control the feed pump for automatic water makeup.
Why Choose McDonnell & Miller
Xylem’s McDonnell & Miller brand is one of the most recognized names in boiler water level controls. Their combination low water cut off and pump controllers are specified by engineers and trusted by service technicians across North America for dependable boiler protection and long service life.
Specifications
- SKU: 42S-HD
- Brand: Xylem-McDonnell & Miller
- Switch Type: SPST Snap Action
- Function: Combination Low Water Cut Off and Pump Controller
- Application: Steam Boilers
- Supply Includes: Head Mechanism Only
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