Begin by pressing and holding both the down and up buttons for a few seconds. The temperature differential for stage one will appear in the display. Release both buttons. Press either the down or up button to select the preferred setting of 1, 2, or 3. If you have a 2 stage thermostat (models 9515 or 9520) wait for approximately 5 seconds and the temperature differential for stage two will begin flashing in the display. Press either the down or up button to select the preferred setting of 2, 3, 4, 5, or 6. Wait approximately 5 more seconds for the display to return to normal.