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Air filter pressure drop

Views:1     Author:Site Editor     Publish Time: 2021-09-08      Origin:Site

What is filter pressure drop?

An air filter’s pressure drop is the measurement of resistance to air that passes through the filter. The more tightly woven or thick a filter’s media is, the more particles and contaminates the filter can trap. This often coincides with a higher MERV rating; however, this also means that the filter is slightly more restrictive and the airflow rate through the filter is lower. 

There is still a common misconception that having a high MERV rated filter will be too restrictive and strain your unit. However, most HVAC systems built in the last 20 years should have no issue using a MERV 6 - MERV 13 rated air filter. You can help minimize the risk of HVAC equipment issues or damage from pressure drop, by regularly changing your air filter. While it is true that the more the air filter traps the more effective it is at capturing more particles; it will eventually become too loaded, at which point, the airflow could be zero and extremely restrictive. Which is not recommended, and could cause increased energy bills, and undue wear on your HVAC unit. Frequent filter changeouts will help minimize risks from pressure drop.air filter skeleton nonwoven fabric factroy - Jiatecairfilter

How is filter pressure drop measured?

Pressure drop is defined by the National Air Filtration Association (NAFA):  The pressure drop of a filter is a measure of its resistance to airflow through it. Resistance is measured in inches water gauge (w.g.) in the Inch-Pound system of measurement. It is measured in Pascals in the SI system.

What initial pressure drop vs final pressure drop?

A filter’s pressure drop is measured twice, once when the filter is brand new and again when the filter has been in service and is “loaded” with trapped air pollutants. The filter’s initial pressure drop (initial resistance) will vary by the filter type, MERV rating, and size. When a filter is in use, it traps and gathers particles, the more particles that are trapped the harder it is for air to pass through; when this occurs the filter’s pressure drop rises. Once the filter is fully loaded the filter will reach its final pressure drop. 

The final pressure drop/final resistance is measured when the filter has reached its total dust holding capacity and is ready to be replaced. It is not recommended to continue to use your filter beyond it’s final pressure drop point. Doing so could cause strain on your HVAC unit and could cause costly maintenance and repairs.

Does air filter's pressure drop change?

As dirt and debris gets trapped by the filter, there is less space for air to pass through, causing the pressure drop to rise throughout the filter’s life. This one of the main reasons why it is so important to check, change, and clean your air filter every month to help ensure your air filter’s pressure drop does not get too high and cause strain on your air conditioner/handler. Remembering to change your air filter is key to reducing the risk from pressure drop.

What is static pressure?

Static pressure is the measurement of the exertion of air flow your HVAC system is moving throughout the system and ductwork.

What are the signs of unhealthy static pressure in an hvac system?

Noisy systems when running, high static pressure could be the culprit. Hot or cold spots throughout your home? This could be because your system is moving too much or not enough air through its ductwork.

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