Difference Between TFA and AHU in HVAC System


TFA and AHU are the very important parts of a Building HVAC System. In this article, we are going to know the actual difference between TFA and AHU. TFA means Treated Fresh Air and AHU means Air Handling Unit. TFA is also known as FAHU or Fresh Air Handling Unit. TFA and AHU almost do the same work but they have different application areas, Advantages, and Disadvantages. Of course, design, construction, and cost also important factors.

Difference Between TFA and AHU


1. The main difference between TFA and AHU is, TFA conditions 100% outside air and feeds to the building inside whereas an AHU conditions 100% existing air inside a building, or sometimes it takes a few outside airs and mixed with the inside air.

2. TFA always installed with an Exhaust System. Because TFA takes outside air and fed to the room inside, so the air pressure inside the room will increase. So, to reduce or maintain the air pressure an exhaust system must be required. On the other hand, AHUs may not require any exhaust system which conditions 100% inside air only.

See the below diagram to better understand.

Difference Between TFA and AHU in HVAC



3. As the TFA conditions 100% outside air so, it consumes more energy than an AHU for the same cooling or heating effect. On the other hand, AHU takes the returned air from the room as input which already cooled or heated. So AHU gives less effort or consumes less energy to make cooling or heating.

4. TFAs are mainly installed where air quality and ventilation are the most important factors than cooling or heating. On the other hand, AHUs are mainly installed where cooling and heating are the most important factors than air quality and ventilation.

5. TFA mainly used for comparatively small places or small rooms whereas AHU mainly used for large spaces, large halls, stores, etc.

6. Most of the TFAs are inbuilt with a Heating and Cooling System, but they also be designed to operate with central cooling and heating system.
On the other hand, most of the AHUs are designed to operate with central heating and cooling system. But AHU with inbuilt heating and cooling system also available.

7. As TFA is used for small places so, they use small motors. In most of the TFAs, the motor and fan are separately installed and they connected with a belt. On the other hand, AHUs are designed for large places, so they used a large size induction motor that directly connected with a squirrel cage type fan.

8. Generally, TFAs are installed outside of the building as they take air from the outside and the treated air from the TFA supplied inside the room by ducts. On the other hand, AHUs are installed inside the building, in fact, they are kept in a separate room(called AHU room). 


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Difference Between TFA and AHU in HVAC System Difference Between TFA and AHU in HVAC System Reviewed by ETechnoG on 3/11/2021 Rating: 5
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