McDonnell & Miller 369-MV Cut Off

For steam boiler applications requiring integrated safety controls, the McDonnell & Miller 369-MV Cut Off (Part Number 155400) provides a robust solution for monitoring critical water levels. This float type low water cut-off is specifically engineered for residential and commercial systems utilizing a millivolt switch, making it an essential component for self-generating gas valve circuits or 24VAC burner systems. It features a 2 1/2" NPT male threaded connection designed for direct mounting into boiler side tappings, with a 1 3/4" insertion length that ensures precise float response within the chamber. With a maximum steam pressure rating of 20 PSI, this mechanical LWCO utilizes dual precision switches to reliably interrupt the burner circuit during low-water conditions while simultaneously providing a secondary circuit to actuate an alarm or an electric water feeder. The automatic reset functionality ensures the system returns to service once safe water levels are restored, provided the millivolt potential is maintained across the specialized contacts.

• Millivolt Compatibility: Equipped with a No. 11-MV switch featuring red terminal panels, specifically rated for millivolt or 24V applications to ensure seamless integration with standing pilot systems.
• Durable Construction: Features packless bellows and a corrosion-resistant monel bellows assembly for long-term reliability in high-heat steam environments.
• Versatile Installation: The adjustable BX outlet allows for flexible conduit positioning, while the 2 1/2" NPT connection simplifies mounting in standard boiler tappings.
• Redundant Safety: Supports the operation of both a low water cut-off and an auxiliary alarm or water feeder, enhancing overall system protection.

• Can this be used on high-pressure steam systems? No, this model is specifically rated for low-pressure steam applications with a maximum steam pressure of 20 PSI.
• Is a transformer required for the millivolt circuit? The 11-MV switch is designed to work directly with millivolt gas valves; however, if using an electric water feeder, a separate 24V or 120V power source may be required depending on the feeder's specifications.
• What is the purpose of the 1 3/4" insertion length? This specific length is critical for ensuring the float mechanism reaches far enough into the boiler shell to accurately detect the water line relative to the manufacturer's minimum safe water level.

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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.