Manufacturer Name: Carrier Product Number: HH84AA021 OEM Part Number: HH84AA021 The Carrier HH84AA021 is a vital component in your Carrier HVAC system, specifically functioning as the main circuit board. This circuit board acts as the of your furnace, regulating various functions like ignition, airflow, and safety features. It receives signals from thermostats and sensors. https://www.partshnc.com/main-circuit-board-3