White-Rodgers 90-T40F3 HVAC Control Transformer

The White-Rodgers 90-T40F3 HVAC Control Transformer is a panel- or equipment-mounted device that steps line voltage down to low-voltage power for HVAC control circuits. It provides low-voltage power to thermostats, relays, contactors, gas valves, and other control devices in residential and commercial systems, with typical installations in furnaces, air handlers, refrigeration units, and HVAC control panels. Built for continuous-duty operation, it delivers stable low-voltage output essential for thermostat communication and reliable control of heating and cooling components. This White-Rodgers transformer (part number 90-T40F3) is commonly used as a replacement in HVAC and refrigeration equipment and is often cross-listed with similar transformers such as Honeywell AT140A, Packard PF42440, and Mars 50354.