Press the up and down arrows simultaneously for 3 seconds and release. Use the Flame/snowflake to move through the setup until you see df for differential. Use the arrows to adjust the differential to desired amount. It is adjustable from .5-3 degrees in .5 degree increments. Press the flame/snowflake button and you will see d2 for second stage differential. Use the arrows to select desired amount which is adjustable from 1-6 degrees in .5 degree increments. Press the flame/snowflake button to show dL for second stage delay. It is adjustable from 5-40 minutes in 5 minute increments. Press the fan button when finshed to return to the main screen.