If the heat exchanger exceeds safe operating parameters—often due to restricted airflow from a clogged furnace filter or a failing blower motor—this switch opens the circuit to kill the gas valve

Conversion from R-12 requires a thorough system flush and an expansion valve adjustment to match the properties of the R-134a refrigerant

240V lead configurations

use 1/4" ID tubing to prevent pressure drop lag

Trane SFTRR75VA Transformer 320819-301 If the heat exchanger exceedsThe Trane SFTRR75VA is a heavy duty 75VA step down transformer engineered specifically for industrial and commercial HVACR control circuits. This multi tap OEM replacement part provides maximum field flexibility, allowing technicians to pull from primary voltages of 120V, 208V, 240V, or 480V to deliver a stable 24V secondary output. Built with a high grade silicon steel core and copper windings, it ensures minimal energy loss and superior thermal