McDonnell & Miller FS7-4WL Snap Switch Freon and the spring-return time is

and the spring-return time is also typically under 15 seconds for rapid fire safety response

This genuine Reznor heating part provides the precise millivolt signal required for modern control modules

This furnace pressure switch features a SPNO (Single Pole Normally Open) contact configuration and is factory-calibrated to a set point of -

Do I need to replace both rings at the same time

Confirming rotation is vital to ensure your heater directs air forward through the heat exchanger

McDonnell & Miller FS7-4WL Snap Switch Freon and the spring-return time isThe McDonnell & Miller FS7 4WL (Part Number 120301) is a heavy duty, industrial grade liquid flow switch engineered for high demand applications requiring precise flow monitoring. Featuring a 1 1 4" NPT connection and a robust SPDT snap switch, this unit is designed for integration into control circuits that signal alarms, start motors, or cycle pumps. The FS7 4WL is built for durability with an extended paddle arm and trimmable stainless steel