McDonnell & Miller 307000 Snap Switch

The McDonnell & Miller 307000 Snap Switch (Model Number FS7-31) is an essential replacement SPDT snap-action switch designed for field repairs of high-performance liquid flow switches and air flow switches. This single-pole double-throw component is engineered to restore precise electrical signaling in the FS7-4 Series, including the FS7-4L, FS7-4S, and FS7-4E hazardous location models. It is also the correct OEM replacement part for AF-1, AF-2, and AF-3 air flow series, as well as VFS series units. Built for industrial durability, the FS7-31 switch assembly handles critical heavy-duty cycles in HVACR systems, ensuring that pump circuits or alarm loops respond accurately to changes in flow velocity. When diagnosing a failed flow switch in hydronic heating or process cooling loops, swapping the 307000 snap switch is a cost-effective alternative to replacing the entire housing, provided the paddle and bellows remain intact. Ensure correct wiring of the common, normally open, and normally closed terminals to maintain system safety interlocks.

Key Benefits for the Job Site

• Broad Compatibility: Drop-in FS7-31 replacement for FS7-4, AF, and VFS series, reducing inventory requirements for service vans.
• SPDT Electrical Versatility: Supports both "make" and "break" circuit configurations for various pump control and boiler safety applications.
• Heavy-Duty Reliability: Rated for high-cycle industrial environments, maintaining electrical contact integrity over long service intervals.
• OEM Precision: Direct McDonnell & Miller 307000 genuine part ensures exact fitment and alignment with existing paddle actuators.

Common Technician Questions How do I test if the 307000 snap switch is faulty? Use a multimeter to check continuity across the COM and NO/NC terminals while manually depressing the actuator arm. If the resistance is high or the circuit doesn't toggle, the internal contacts have likely pitted or failed. Can the FS7-31 be used in hazardous location flow switches? Yes, the 307000 is the designated replacement switch for the internal components of the FS7-4E and FS7-4SE explosion-proof series. Does this switch include the paddle or bellows? No, this part is the electrical snap switch only. If the bellows are leaking or the paddle is damaged, a full head assembly or a complete replacement unit is required.

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.