McDonnell & Miller 63-M-HD Head Mechanism 30067439-890 it is technically best practice

it is technically best practice to install it in a position where gravity doesn't compete with the internal spring

this unit provides a stable 240V secondary output

which can be trimmed to fit specific cabinet depths if necessary

it requires a minimum pressure differential of 5 PSI to move the internal diaphragm and open the flow path

or use a multimeter to verify the microfarad reading is within the 145-175 range

McDonnell & Miller 63-M-HD Head Mechanism 30067439-890 it is technically best practiceThe McDonnell & Miller 63 M HD Head Mechanism (Part Number 143200) is a heavy duty replacement head mechanism designed for the Series 63 Low Water Cut Off. Engineered for both hot water and steam boilers, this manual reset mechanical control ensures critical safety by interrupting the electrical circuit to the burner in 15 psi steam or 50 psi water applications. It features a robust float operated design and includes the No. 2 M switch, providing