McDonnell & Miller 63HD Replacement Head Mechanism with No. 2 Switch

The McDonnell & Miller 63HD (part number 142600) is a replacement head mechanism designed specifically for Series 63 low water cut-off controls. This head assembly provides a complete rebuild solution for steam and hot water boiler protection systems without the need to remove the entire unit from the piping.

Key Features:

• Complete head mechanism assembly with integrated No. 2 switch with automatic reset
• Compatible with Series 63 low water cut-off controls for steam and hot water boilers
• Designed for systems up to 50 PSI maximum pressure
• Quick and easy replacement by simply removing float chamber bolts—no piping disruption required
• Suitable for residential, commercial, and industrial boiler applications
• Manufactured in the United States by McDonnell & Miller, a Xylem brand

This head mechanism includes everything except the float chamber, allowing technicians to service and restore low water cut-off functionality efficiently. The integrated automatic reset switch ensures reliable boiler protection by automatically shutting down the system when low water conditions are detected.