McDonnell & Miller FS5-3-4IN-NPT Flow Switch

The McDonnell & Miller FS5-3-4IN-NPT Flow Switch is an inline flow-detection device that senses the movement of liquid through a piping circuit and produces a switch output suitable for triggering downstream equipment, alarms, or control logic. The model designation FS5-3-4IN-NPT identifies a 3/4-inch NPT threaded connection, enabling straightforward installation into standard piping configurations and compatible with typical 3/4-inch NPT fittings. As part of the FS5-3 family, this flow switch functions to indicate flow presence to a control system, providing a binary signal that can be used for automation, interlocks, or process monitoring and can be wired to conventional relay or controller inputs. Manufactured by McDonnell & Miller, the FS5-3-4IN-NPT is a dedicated component for fluid-handling systems where a mechanical flow-detection device is required to confirm whether liquid is moving. In operation, flow switches like this provide a simple, dependable method to verify that liquid is moving and to initiate responses in automation or safety circuits.