Cleveland Controls NS2-1227-02 Pressure Switch 320720-756 The spring return is a

The spring return is a safety feature that uses stored mechanical energy to return the actuator to its "home" position (either fully open or fully closed) immediately if the 24V power supply is interrupted

This part is the liquid line tube assembly itself

ensuring reliable combustion for models like the Reznor RDF

while the secondary side provides 24VAC control power for the thermostat and relay coil

Cleveland Controls NS2-1227-02 Pressure Switch 320720-756 The spring return is aThe Cleveland Controls NS2 1227 02 Pressure Switch is a high performance OEM replacement airflow sensor engineered for precise monitoring of positive, negative, or differential air pressure in HVAC induction systems and furnace draft control. This NS2 series air pressure switch features a durable, glass filled polycarbonate housing that ensures thermal stability and contaminant free operation in demanding commercial and residential environments.