The McDonnell & Miller FS7-4E (Part Number 120100) is a heavy-duty industrial liquid flow switch designed specifically for hazardous environments. Featuring a NEMA 7 and 9 explosion-proof enclosure, this unit is rated for Class I, Groups C and D, and Class II, Groups E, F, and G, ensuring safe operation in volatile atmospheres. The 1 1/4" NPT brass body utilizes a sealed tube construction and a magnetic switching mechanism to provide reliable SPDT snap switch logic for pump control or low-flow protection. Engineered for high-pressure systems up to 300 PSI, the FS7-4E includes trimmable stainless steel paddles to accommodate pipe sizes from 1 1/4" to 6". A dedicated sensitivity adjusting screw allows technicians to fine-tune flow and no-flow setpoints in the field. This liquid flow switch supports a maximum liquid temperature of 300°F and a maximum flow velocity of 10 feet per second, making it a rugged choice for commercial boilers and process cooling loops. Key Benefits for Contractors Hazardous Location Rated: Integrated NEMA 7/9 enclosure eliminates the need for external explosion-proof housing in Class I and II environments. Versatile Piping Integration: The 1 1/4" NPT connection and trimmable paddles allow for precise fitment in various industrial line sizes. High Pressure Durability: Rated for a maximum operating pressure of 300 PSI, suitable for demanding hydraulic and hydronic applications. Maintenance Friendly: The magnetic switching mechanism separates the electrical components from the fluid media, reducing the risk of seal failure. Common Questions & Technical Insights How do I adjust the sensitivity for low-flow applications? Use the sensitivity adjusting screw located under the housing to modify the force required to actuate the SPDT snap switch. Rotating the screw changes the spring tension against the paddle arm. Can this switch be used in vertical piping? The McDonnell & Miller FS7-4E is designed for horizontal pipe runs. Installation in vertical lines is generally not recommended as gravity can affect the paddle's return-to-center position, leading to inaccurate flow detection. What is the maximum fluid velocity for this model? To prevent paddle damage or erratic switching, ensure the system velocity does not exceed 10 feet per second (3 meters per second). This item is not eligible for free shipping. 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.
