Description
Product Overview
The Xylem-McDonnell & Miller 150S-M-HD is the replacement switch head mechanism for the 150S-M-HD combination low water cut-off and pump controller. Designed for steam and hot water boilers, this head mechanism provides dependable low water protection and pump control in a single, compact assembly. The snap-acting SPDT (Single-Pole Double-Throw) switch with manual reset ensures the boiler will not restart automatically after a low water condition — a critical safety feature that requires operator acknowledgment before resuming operation.
Key Features
- Combination low water cut-off and pump controller in one unit
- Snap-acting SPDT switch for positive, reliable switching action
- Manual reset design — requires deliberate operator reset after low water event
- Head mechanism only — replacement component for existing 150S-M-HD installations
- McDonnell & Miller proven reliability for steam and hydronic boiler protection
- Part Number 173203
Application
The 150S-M-HD head mechanism is designed for use on steam boilers and hot water heating systems where a combination low water cut-off and pump controller is required. The manual reset SPDT switch head is the ideal replacement when the existing switch mechanism needs to be serviced or replaced without disturbing the float chamber or boiler piping. It is suitable for residential, light commercial, and commercial boiler installations.
Why Choose Manual Reset?
A manual reset low water cut-off is recommended in applications where it is critical that a technician or operator physically inspect the cause of a low water condition before the boiler is allowed to fire again. This prevents repeated cycling on low water, protects the boiler from heat damage, and ensures compliance with many insurance and code requirements for commercial boiler installations.
Brand
McDonnell & Miller, a brand of Xylem, has been the industry standard for boiler low water cut-offs and pump controls for over a century. Their products are trusted by engineers, contractors, and building operators across North America for dependable boiler protection.
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