McDonnell & Miller 94 Controller

Working on a high-pressure system requires reliability that won't flake out when the building's steam demand peaks. The McDonnell & Miller Series 94 (Part Number 165200) is a heavy-duty combination low water cut-off and pump controller specifically engineered for commercial and industrial steam boilers. Rated for a maximum pressure of 250 PSI, this unit uses a unique magnetic repulsion mechanism that completely eliminates the need for a bellows—removing a common failure point found in lower-tier controls. It comes standard with two snap-acting SPDT switches (the No. 5 switch) to provide independent control for the boiler feed pump and a low-water burner cut-off or alarm circuit. Whether you are installing a new primary control or looking for a drop-in replacement, the Series 94 delivers consistent water level management regardless of steaming capacity.

Key Benefits for Contractors

• 250 PSI Pressure Rating: Built for high-pressure steam applications where standard 150 PSI controls won't meet the spec.
• No Bellows Design: Uses magnetic force to actuate switches, preventing the leaks and fatigue failures common in bellows-style units.
• Dual SPDT Functionality: Integrated No. 5 switch manages both pump control and low water cut-off in one robust housing.
• 1-1/4" NPT Connections: Standard threaded connections for high-capacity flow and stable mounting on equalizing pipes.
• Interchangeability: The 165200 complete unit is fully compatible with 94-HD head mechanisms (165300), allowing for chamber-in-place rebuilds.

Common Questions

Can I use this on a low-pressure boiler?
Yes. While it is rated for up to 250 PSI, it operates effectively on any steam boiler regardless of its steaming capacity, provided the 1-1/4" NPT tappings match your manifold.

What is the difference between the 165200 and the 165300?
The 165200 is the complete assembly including the float chamber. The 165300 is the head mechanism only, which is used for rapid service when the existing casting is still in good condition.

Does this unit support manual reset?
This specific model (165200) has an automatic reset. If your local code requires a manual reset for the low water cut-off, you would need the 94-M version or a 166000 head mechanism.

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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.