This can be normal to ensure good airflow and cooling effect if the duct with greater airflow is supplying a larger area. However, if you are unsure you need to contact the company who installed the ducted evaporative cooling system and ask them to balance your airflow within the ductwork. This cannot be achieved by any adjustment on the evaporative air cooler. If you have moved into a house with a system already installed and you don’t know who installed it, you can get someone who is qualified in ductwork design to balance the system. To find your local dealer visit Find a Dealer.