Fresh Air Calculator for AHU Working with VAV System

Air handling units (AHU) are the lungs of any HVAC system. An air handling unit is a device used to regulate and circulate air as part of the heating, ventilation and air conditioning system. The AHU takes in outside air, filtered and either heated or cooled and supplies it as fresh air to the air conditioned room.

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Fresh Air Calculator For AHU Working With VAV System

Fresh Air Calculator For AHU Working With VAV System

The amount of fresh air needed to be supplied to an air handler in an air conditioning system is a function of the following:

Regional and local outside air quality: If the outside air contains higher pollutant levels, then appropriate filtration is essential prior to supplying to the air handling apparatus.

Volume: There are standard air changes per hour defined in the aforementioned standard. Normally for a comfort application - ACPH is considered 1 to 2 ACPH.

Occupancy: There are standards for the fresh air flow rate needed per occupants which depend on the kind of work the occupants do and the smoking levels.

Infiltration: It is important that a little more than the infiltrating air quantity is added in the fresh air path of the AHU to offset the infiltrating air so that the pressure inside the room is higher than the pressure from outside. Thus, the design capacity of AHU and hence load on refrigerating equipment increase with increase in infiltration.


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