McDonnell & Miller 309100 Switch

The McDonnell & Miller 309100 Switch, also known as the Model Number 11 Switch, is a heavy-duty replacement switch kit designed for field repairs of float-type low water cut-offs. Engineered for automatic reset operation, this unit features two SPST switches that allow for simultaneous control of a burner circuit and a secondary function, such as an electric water feeder or a low water alarm. It is fully compatible with Series 61, 64, 67, 69, 764, and 767 controls, providing a reliable mechanical interface for 24Vac, 120Vac, and 240Vac power supplies. As a general purpose switch, it ensures proper boiler safety by breaking the burner circuit during low-water conditions while providing high-amperage switching capacity (up to 7.4 FLA at 120V) to handle HVAC repair requirements in both residential and commercial steam systems.

• Broad Compatibility: Standardized fit for McDonnell & Miller Series 67 and other low water cut-off units.
• Dual Control Logic: Includes two single-pole single-throw mechanisms to manage both the burner and an auxiliary alarm or feeder.
• Universal Voltage: Rated for 24V/120V/240V, allowing for flexible integration into various HVAC control systems.
• Field Serviceable: Simplifies repairs by allowing the replacement of the internal switch mechanism without removing the entire control body.

Which terminals are used for the burner and water feeder?
Terminals 1 and 2 are typically dedicated to the burner circuit (low water cut-off), while terminals 3 and 4 are utilized for an electric water feeder or a low water alarm.

Can this replace a manual reset switch?
The 309100 is an auto-reset switch. If your system requires a manual reset for safety compliance, ensure you are utilizing the correct model for your specific boiler application.

Is this compatible with Series 69 controls?
Yes, the Model 11 switch is the standard replacement for Series 69 and Series 767 low water cut-offs used on residential steam boilers.

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.