Economizer in HVAC as its name implies is a device that is used to save energy consumption by using the cool air from outside of a building to cool the internal space. It usually works together with the air conditioning system in the building and can cut the electricity cost up to 60% or more depending on the outside climate and the cooling loads required.
Getting fresh air from outside the building will also help to replenish the oxygen level and reducing the carbon dioxide level in the building. This helps to ensure that the occupants always have good quality of air hence increasing work productivity. This device is most suitably used in temperate climate countries and is not suitable for use in hot and humid climates.
The control will determine how wide the damper is to open to draw the outside air and for how long by monitoring the conditions of the indoor temperature, outdoor temperature, humidity levels, carbon dioxide level and other parameters.
It can be used in the air-side type or water-side type. Air-side uses the cool air from outside of the building to cool the internal building whereas water-side uses the natural cool air to cool the water tower.
The typical device consists of a combination of dampers, motorized actuator to open or close the damper blades, sensors, linkages and electronic controller. Depending on the model, it can also interface with building management system.
As there are many mechanical parts that are involved, regular preventive maintenance is always advisable to ensure that the dampers and other actuators are working well. Dampers that are damaged, for instance if they are permanently open will cause the loading condition to increase rapidly hence instead of saving energy, it may cause substantial energy consumption.
During winter or cooler days when the outside humidity level is high, the damper's opening will be reduced to allow only 10% to 20% of fresh air into the building. Bigger building management air conditioning system or heating system will operate simultaneously with the economizer.
When summer comes but outdoor temperature is still lower than indoor, the damper blades will open more to allow more fresh air into the building.
Similarly, if the carbon dioxide level is higher than the set threshold in the building, the damper will also open more to allow more air into the building. Filters are usually installed to filter the outside air from any contaminants before being allow to come into the building.