Dynamic Airflow Balancing DAB

Dynamic Airflow Balancing, DAB is unique for a few reasons besides the remote monitoring and control that comes with all of 75F software services.

1. With continuous commissioning DAB is frequently adjusting damper positions to redirect the air in a single duct run to where it is needed.
2. On the assumption that as long as the airflow is not restricted below 70% no harm will be done to the unit, the DAB system profile will have no less than an average 70% damper position at any given time. 
3. DAB has a damper on each diffuser making for a more granular zoning solution.

Space Dampers

We will use a 3 zone example to demonstrated how the DAB algorithm works. For simplicity of explanation this example is assuming the human and electronic loads in each space are equal and that all variation in the load is coming from the sun. 

Image 1 - This is a typical morning where the sun is coming up in the east. You can see the zones on the east temperatures are getting warm. The DAB algorithm will continuously tweak the damper positions to allow the most cold air to flow to the east side of the building while limiting the amount of air on the west side. 

Image 2 - Mid day the loads from east to west are starting to even out. Here the damper positions are going to begin evening out throughout the building. 

Image 3 - Late in the day the sun will be to the West side of the building and you see the damper positions are opening wide in the West and closing in the East to direct the air where it is needed. 

System

Most buildings are not so simple as the example used for damper positions and may have more varied loads in which a decision must be made as to what operational mode the system should be in and when to actually heat or cool. Unlike a standard thermostat where you only have a single temperature reading, with DAB you are now reading temperatures from all spaces on a single duct run. Using a weighted average current/ desired temperature the system will automatically determine what mode to operate in. Lets view a few examples to demonstrate.

Image 4 - the number of zones requiring heating outweighs the zones calling for cooling.

Image 5 - Now the same number of zones are calling for cooling as before but the two zones calling for heating combined have a lower demand, so the system would be in cooling mode here. 

Image 6 - See the same example as example 2 with the addition of zone priority. When you add in the zone priority with the same temperatures, instead of the unit heating, it now decides to cool.