McDonnell & Miller 94-M-HD Controller

Replace your compromised boiler controls with the McDonnell & Miller 94-M-HD Controller (Part Number 166000). This heavy-duty head mechanism replacement is engineered for steam boiler water level control in high-pressure commercial and industrial environments. It functions as a combination low water cut-off and pump controller, utilizing a magnetic repulsion system that eliminates the common failure points found in bellows-operated units. Designed for a maximum pressure of 250 PSI, the 166000 features two snap-acting manual reset SPDT switches (No. 5-M series) to provide precise burner cut-off and feed pump activation. This mechanism is compatible with Series 94 and Series 194 castings, featuring a 10-bolt flange design for secured, leak-proof integration. Whether managing fluctuating steaming capacities or requiring a rigid safety interface, this manual reset boiler control ensures the burner remains locked out until an operator manually acknowledges the low-water condition, protecting the heat exchanger from dry-fire damage.

• Magnetic Repulsion Technology: Eliminates the need for bellows, significantly reducing the risk of mechanical fatigue and leaks in high-pressure systems.
• Dual Switch Logic: Includes a No. 5-M switch assembly to independently manage the boiler feed pump and the burner circuit.
• High-Pressure Rating: Rated for up to 250 PSI, making it suitable for both low and high-pressure process steam applications.
• Manual Reset Safety: Prevents automatic burner restart after a low water event, forcing a manual inspection of the boiler water level.
• Universal Component Fit: Designed as a direct head mechanism replacement for existing Series 94 combination LWCO and pump controllers.

Is the gasket included with the 94-M-HD head mechanism?
Standard head mechanisms generally require a separate 10-bolt flange gasket (Part No. 92-68) for a proper seal. It is best practice to install a new gasket during any head replacement to prevent steam bypass.

Can I use this to replace an automatic reset model?
Yes, if the application or local code requires a manual reset low water cut-off, the 94-M-HD (166000) can replace an automatic 94-HD, provided the wiring is updated to accommodate the manual reset switch logic.

Does this assembly include the float and rod?
Yes, the 166000 head mechanism is a complete internal assembly including the mounting plate, snap-acting switches, float, and rod. It does not include the outer cast iron body.

This item is not eligible for free shipping.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.