Goodman 80 000 BTU 80% AFUE Upflow/Horizontal Gas Furnace model GMH80803BN Two stage gas valve control technology enables the installer to activate the 2 stage valve with the flip of a dip switch Control board has the provision to store the last 5 diagnostic codes in memory Low Voltage terminals and extra provisions for the 24 volt humidifiers and air cleaners Using self adjusting features, the furnace gets adjusted automatically to a high- or- low stage operation based on the temperature outside without any outdoor temperature sensor Low Constant fan enables the users to activate the low heat speed to ensure efficient circulation of air throughout the home