Hey, could you guys tell me the difference between a VFD and VAV ?

Question

These are used for Air Conditioning the buildings .

Answer 1

VAV: Variable Air Volume
VFD: Variable Frequency Drive

My guess: They are using a VFD to adjust the motor speed on a fan (blower) to get VAV for the HVAC.

Answer 2

A variable frequency drive (VFD) is an accessory to a motor which allows the speed (RPMs) of the motor to be varied. In HVAC, they may be used on AHU fans, pumps, and cooling towers to reduce energy used by those motors during times of off-peak loading.

A Variable air volume (VAV) refers specifically to air handling systems. You supply air at a medium-to high pressure to a VAV box, which is essentially a combo pressure relief valve and control damper. As the thermostat in the area served by the individual box is satisfied, the VAV damper closes. The more dampers that are closed (for example, off-peak cooling load), the more pressure builds up in the primary ductwork. Sensors sense the pressure increase and slow the supply air fan (using a VFD) accordingly.

Answer 3

First answer is correct.

So your air handling unit must have a single VFD drive on each fan(s), and throughout the HVAC system, you can have several VAV boxes to control air flow to each area.

Answer 4

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