There are three common reasons why an outside damper is open during a heating, cooling, and/or fan cycle:
An economizer cycle is active:
If the Pelican PEARL has decided that the outdoor air can be used to cool the room, it will open the outside damper.
A ventilation cycle active:
If a Pelican thermostat is running a Fan, Cool, or Heat cycle, the Pelican PEARL will place the outdoor damper at the configured Minimum Damper Position.
Note: If the PEARL is also controlling a Variable Speed Supply Fan, the Minimum Damper Position will automatically adjusts in proportion to how fast the supply fan is running. For example, at the fasted configured fan speed, the outdoor damper will be at the configured Minimum Damper Position. And as the fan speed is ran slower, the outdoor damper will open further.
A demand ventilation cycle active:
Anytime the CO2 levels exceed the CO2 Ventilation configuration, the Pelican thermostat will start a Demand Ventilation Cycle. The Pelican PEARL will increase the ventilation rate, beyond the Minimum Damper Position, as the CO2 levels rise.
Note: The PEARL will never open the outdoor damper, during a Demand Ventilation Cycle, further than its configured Maximum Ventilation Position.