Resideo AT40A1139 Transformer R-407A Environmental Resilience: Features a rugged

Environmental Resilience: Features a rugged housing designed to withstand extreme thermal cycles from -40°F to 190°F without calibration drift

flow enters from both Port II (A) and Port III (B) and exits through Port I (AB)

Why is there no spark when I press the test button

Does this kit include an alarm circuit

Technicians should measure the micro-amp (µA) signal in series with the sensor wire while the burner is lit

Resideo AT40A1139 Transformer R-407A Environmental Resilience: Features a ruggedThe Resideo AT40A1139 Transformer is a heavy duty 40VA power supply designed for reliable 24V control circuits in residential and light commercial HVACR applications. Engineered with a 240V primary and a 26. 5V secondary output, this NEMA Type D transformer ensures consistent voltage regulation for thermostats, zone valves, and gas valves. The channel frame mounting configuration allows for versatile installation directly onto a junction box or