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What is Static Pressure?

Static pressure. It might sound harmless, but it affects the entirety of your HVAC system. In this video we’ll discuss what it is and how to avoid it.

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July 13th, 2021

Static pressure. It might sound harmless, but it affects the entirety of your HVAC system. In this video we’ll discuss what it is and how to avoid it.

Hi, I’m Roger with Fire & Ice. Over the years our service techs have gone out on a call to “repair” a system that has completely shut down. They later find the problem to be high static pressure due to a clogged furnace filter. In this video we’ll go over how a furnace filter can cause high static pressure and discuss:

  • What is static pressure?
  • How do filters contribute to static pressure?
  • When to change your furnace filter?
  • And finally, what can you do right now?

What Is Static Pressure?

Let’s begin and determine what static pressure is. Simply put, it is the resistance experienced by air as it passes through your HVAC system. It’s a lot like blood pressure in your body. Too much static pressure can cause strain on your system, reducing its performance, and can result in wasted energy. If left untreated it can result in premature failure of the system. 

The best way to maintain optimal static pressures is to have properly sized equipment and ductwork installed correctly in your home. Additionally, regularly changing your air filter will help maintain static pressure levels.

How Does Your Equipment and Ductwork Affect Static Pressure?

In an HVAC system air is collected from the home by a blower motor inside your furnace, conditioned, and then recirculated throughout the house. When your HVAC system is dialed in, air is able to move freely throughout the ductwork and into your home with optimal static pressure levels. 

HVAC manufacturers have a preferred range for static pressure levels with their equipment. When static pressure levels fall above or below that range can cause damage to your HVAC equipment.

There are a number of contributing factors that can cause increased static pressure such as:

  • The size of your furnace has a lot to do with static pressure levels in your home. An oversized furnace can be too powerful and can cause high static pressure inside your ductwork. While an undersized furnace won’t be able to move enough air through the system to keep you comfortable.
  • Second, is the size of your ductwork. If the ductwork in your home is too small the air moving inside can become too restricted and cause high static pressure. Conversely, if your ductwork is too large the static pressure becomes too low and can rob you of your comfort.
  • Third, is the installation of equipment and ductwork inside your home. Improper installation or too many bends and turns in your ductwork can negatively affect static pressure levels.
  • Fourth is a dirty or clogged air filter.

The best way to maintain optimal static pressure levels is to have load calculations performed to determine the correct size system for your home and to determine any modifications that your ductwork may need. 

In fact, a lot of the estimates we provide here in Central Ohio include the replacement of return air drops because past HVAC systems were undersized. Having a qualified HVAC professional determine the right size system for your home is critical in maintaining optimal static pressure levels. 

How Do Filters Contribute to Static Pressure?

A furnace filter is designed to remove debris from the air. As time goes on, the debris builds up and restricts the amount of air that is able to flow through the filter. Restricted airflow causes an increase in static pressure. This airflow backup makes your system work harder and in the short-term cause:

  • Pockets of hot and cold spots in your home from a lack of airflow coming from the vents
  • Noisier operation as your system works harder
  • Longer run times resulting in higher energy bills
  • And overall, less comfort in your home
  • Long-term effects of high static pressure can result in:
  • Leaks in your ductwork
  • A significant reduction in your system’s lifespan

When to Change Your Furnace Filter?

All filters come with a recommended replacement schedule on their packaging. Some are as early as 30 days while others need to be changed once a year. It’s recommended that you stick to your filter’s replacement interval. Otherwise you may experience an increased static pressure in your system.

However, in some instances you may need to change your filter more often to maintain proper airflow. For example:

  • Pets are notorious for shedding and dander can cause filters to need replaced sooner.
  • During allergy season the increase of pollen in the air may cause your filter to clog quicker.
  • Smokers who smoke inside may find themselves needing to change their filters more often. Particulates found in smoke can build fast in filters.
  • Lastly, the frequency your system runs will also increase the use of your filter.  
  • Continuously running your system will cause your filter to need replaced sooner.

Other signs it's time to change the filter can be seen around the home. Are you starting to notice strange smells? Does dust seem to accumulate more quickly than usual? These could be signs that your filter has become dirty and less efficient and needs to be replaced.

What are the next steps?

I hope by now you have a better understanding of how your furnace filter contributes to static pressure levels in your HVAC system. Changing your filter on a regular basis is one of the easiest ways to maintain optimal static pressure levels in your HVAC system. If you’d like to learn more about filters or you need to order a new filter, click the link in the description below. Thank you for watching and we look forward to making your day even better.

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