McDonnell & Miller 61-HD Low Water Cut Off

The McDonnell & Miller 61-HD (Part Number 140300) is a heavy-duty mechanical low water cut-off designed specifically for low-pressure steam boiler applications. This head mechanism serves as a direct replacement component for Series 61 controllers, facilitating reliable burner circuit interruption when water levels drop below the safe line. Rated for a maximum steam pressure of 20 PSI, the 61-HD utilizes a high-buoyancy float-operated mechanism to actuate the integral switch. This unit is optimized for large-capacity residential or commercial steam systems requiring a float-type safety control with a 1" NPT connection. The 61-HD head mechanism is engineered for field serviceability, allowing contractors to restore system safety without replacing the entire housing. Its robust construction ensures precise low water safety monitoring and consistent performance under standard operating temperatures, making it a critical boiler safety control for maintaining the operational integrity of heating systems.

• Universal Series 61 Compatibility: Designed as a drop-in replacement head for all McDonnell & Miller 61-series mechanical controls.
• Heavy-Duty Switch Action: Features a high-capacity switch designed to handle high-amperage burner circuits without premature failure.
• Float-Operated Precision: Uses a mechanical float for steam boiler water level detection, ensuring operation even during power fluctuations.
• Simplified Maintenance: Replacing the 140300 head mechanism reduces labor time and avoids the need for complex pipe fitting during repairs.

Does the 61-HD include the float chamber housing?
No, this is the head mechanism only. It is intended for installation into an existing Series 61 housing body for low water cut-off replacement.

What is the maximum pressure rating for this LWCO?
The 61-HD is rated specifically for low pressure steam systems with a maximum operating pressure of 20 PSI (1.4 kg/cm²).

Can this be used for hot water boiler applications?
The 61-HD is specifically engineered for steam boilers. For hot water applications, consult technical specifications for compatible 764 or 63 series controls.

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.