McDonnell & Miller 94-7B Pump Controller

The McDonnell & Miller 94-7B (Part Number 166300) is a heavy-duty combination low water cut-off and pump controller specifically engineered for high-pressure industrial and commercial steam boiler applications. Built to handle a maximum pressure of 250 PSI, this unit ensures precise water level management across any steaming capacity. It features a No. 7B proportional switch with a 135-ohm potentiometer signal, allowing for seamless integration with modulating feed water valves to maintain a constant, steady waterline. Unlike standard controls, the Series 94 uses magnetic repulsion to actuate the switches, completely eliminating the need for a bellows—a common failure point in high-pressure environments. This float-operated assembly includes 1-1/4" NPT equalizing tapping connections and an automatic reset function. For technicians replacing older boiler water level controls, this model provides the reliable, mechanical redundancy required to prevent dry-firing and ensure operational safety in demanding steam systems.

• Bellows-Free Design: Uses magnetic repulsion to operate switches, increasing durability in high-pressure steam environments.
• Proportional Control: The integrated 7B potentiometer switch provides a 135-ohm signal for modulating pump or valve control.
• High-Pressure Capability: Rated for systems up to 250 PSI, making it suitable for industrial high-pressure steam boilers.
• Universal Capacity: Designed to maintain consistent water levels regardless of the boiler's steaming capacity or throughput.
• Robust Construction: Features a 10-bolt flange design and heavy-duty casting for long-term field reliability.

• Can this be used as a primary or secondary cut-off? Yes, the 94-7B is commonly used as a primary pump controller and low water fuel cut-off, but it can also serve as a secondary safety device.
• What does the 7B switch do differently than a No. 5 switch? The 7B switch provides a proportional 135-ohm signal for modulating feed water systems, whereas a No. 5 switch is generally for on/off pump control.
• Is the replacement head compatible with existing Series 94 bowls? Yes, the 166400 replacement head mechanism can be installed onto existing float chambers to simplify maintenance without disturbing boiler piping.

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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.