McDonnell & Miller FS7-4SJ Snap Switch 30067439-890 The International Environmental 71520318 is

The International Environmental 71520318 is a high-performance digital non-programmable fan coil thermostat engineered for precise climate control in commercial and residential 2-pipe and 4-pipe hydronic systems

You must pair it with an RA2000 operator (sensor/dial) to achieve automatic temperature control

ensuring stable control and preventing pressure surges during modulation

which is critical for preventing premature coil burnout during continuous operation

McDonnell & Miller FS7-4SJ Snap Switch 30067439-890 The International Environmental 71520318 isThe McDonnell & Miller FS7 4SJ (Part Number 120171) is a rugged, industrial grade liquid flow switch designed for high pressure applications where standard brass units fall short. This SPDT snap switch features a durable stainless steel body and wetted parts, allowing it to withstand a maximum pressure of 1000 PSI. Built with a 1 1 4" BSPT connection, it is engineered for precise flow sensing in large pipe systems across hydronic heating, industrial