McDonnell & Miller 67-LQHU Low Water Cut Off

The McDonnell & Miller 67-LQHU (Part Number 149500) is a field-proven mechanical low water cut off engineered specifically for residential and commercial steam boiler applications. Operating as a float-type safety control, this unit is designed to interrupt the electrical circuit to the burner if water levels drop below the safe operating line, preventing catastrophic dry-fire conditions. The 67-LQHU model is identical to the 149500 and features a 3/4" NPT control connection, specifically configured without the quick hook-up fittings to allow for specialized piping requirements. It supports a maximum boiler pressure of 20 PSI and utilizes the reliable No. 11 automatic reset switch.

Built for durability in demanding environments, the 149500 includes a large float chamber and a lever-operated full-port ball valve, which facilitates rapid and effective blow-down for sediment removal. This float-operated LWCO is compatible with 120V, 240V, or 24V circuits, making it a versatile choice for standard steam heating systems. Its dual precision switches also permit the simultaneous operation of an alarm or an electric water feeder, ensuring the boiler remains within optimal parameters while providing clear notification of low-water events.

• Direct 3/4" NPT integration: The "LQHU" version (Less Quick Hook-Up) provides maximum flexibility for installers working with custom piping configurations.
• Sediment Management: Features a high-flow blow-down valve to ensure the float chamber remains clear of scale and sludge.
• Universal Application: Rated for steam boilers of any steaming capacity with a pressure ceiling of 20 PSI.
• Multi-Voltage Compatibility: The No. 11 switch handles various industrial voltages for broad system compatibility.
• Reliable Auto-Reset: Ensures the burner resumes operation automatically once safe water levels are restored, reducing unnecessary service calls for simple level fluctuations.

What is the difference between the 67 and the 67-LQHU?
The 67-LQHU (149500) is functionally identical to the standard Series 67 but is supplied without the quick hook-up fittings. This is the preferred choice when the boiler tappings do not align with standard sight glass spacing or when hard-piping the control is required.

Can this unit be converted to manual reset?
Yes. While this model ships with an auto-reset switch, it can be converted in the field by installing a McDonnell & Miller manual reset switch assembly if local codes or specific safety protocols require it.

How often should the blow-down valve be operated?
For optimal performance and to prevent float binding, the lever-operated ball valve should be flushed weekly during the heating season to remove accumulated solids from the float chamber.

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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.