Static pressure in Air Handling Unit

[cktan22]

what will happen if static pressure in supply duct is higher than the fan compartment in AHU?? or vice-versa
thanks

 

[russ_watters]

I'm not very clear on what you are asking. What exactly do you mean by "fan compartment"? Do you mean a discharge plenum? (Note: not all fans have a discharge plenum.) The static pressure in the supply duct cannot be higher than in a discharge plenum. It isn't physically possible as per Bernoulli's principle. The static pressure in the discharge plenum will always be higher than in the supply duct.

 

[cktan22]

what i mean is, the static pressure for hot return air ( red colour arrow) and the static pressure for cold supply air ( blue colour) in the AHU as shown in the picture. What is the effect if the static pressure for blue colour arrow is greater than red colour arrow and vice-versa?
thank for reply.

 

[russ_watters]

The two are not related to each other, so there is no effect. But it is typical for the return static to be lower (in absolute value) than the supply static because of downstream control and distribution devices in the supply duct.

 

[PJC01]

I would like to first clarify that the static pressure in an Air Handling Unit (AHU) refers to the pressure exerted by the air in the ductwork. This pressure is caused by the resistance of the ducts, fittings, and equipment in the system.

If the static pressure in the supply duct is higher than the fan compartment in the AHU, it means that the air is being pushed through the system with more force than it is being pulled by the fan. This can happen due to a variety of reasons such as a clogged filter, closed dampers, or a malfunctioning fan.

In this scenario, the fan will have to work harder to overcome the higher static pressure and maintain the required airflow. This can result in increased energy consumption and strain on the fan, potentially leading to its failure. It can also cause uneven distribution of air throughout the system, leading to poor indoor air quality and discomfort for occupants.

On the other hand, if the static pressure in the fan compartment is higher than the supply duct, it means that the fan is pulling more air than the ducts can handle. This can happen if the ducts are too small or if there is a blockage in the supply duct. In this case, the fan will be working efficiently, but the air distribution will be affected, resulting in uneven temperatures and potential equipment damage due to overworking.

In either case, it is important to maintain proper static pressure in the AHU to ensure efficient and effective operation of the system. This can be achieved through regular maintenance and monitoring of the system's components. Any imbalances in static pressure should be addressed promptly to avoid potential issues and maintain optimal indoor air quality.