As an HVAC expert, I have seen firsthand the consequences of using incorrectly sized furnace filters. Many homeowners are not aware of the importance of properly fitting filters and the potential damage that can occur if they are forced into place. In this article, I will explain why furnace filters must be the exact size and how to determine the correct dimensions for your specific HVAC unit. First and foremost, it is crucial to understand that furnace filters should be securely adjusted, but not forced into place. If you find yourself having to push or bend the filter to fit it into its slot, it is most likely too large.
Forcing an incorrectly sized filter can cause damage and reduce its effectiveness in cleaning the air. This is why it is essential to know the exact size of your air filter before purchasing a replacement. In some cases, HVAC units may require custom filters with unique or unusual dimensions. This means that you will need to order a filter specifically tailored to your unit. The actual size of a filter refers to its exact dimensions when measuring length, width, and depth (thickness).
This measurement is then rounded up and used as the nominal size, which is commonly seen on air filter packaging. However, understanding the difference between nominal and actual sizes can be confusing for those who are not familiar with HVAC systems. When shopping for air filters online, it is crucial to know that there are two sizes to consider: nominal and actual. The nominal size is the rounded measurement used on packaging labels, while the actual size refers to the exact dimensions of the filter. Using an oversized filter can cause damage to your HVAC system and compromise its ability to clean the air effectively.
Therefore, it is essential to learn how to measure your air filter correctly. To determine the nominal size of your filter, round the actual dimensions to the nearest inch. This is the measurement you will use when purchasing a replacement filter. It is crucial to note that using an incorrectly sized filter can allow dust, dirt, and germs to bypass the filter and recirculate in your home's air. This can lead to health issues and decreased air quality.
When I was searching for a new air filter for my own home, I came across a company that had a very informative YouTube video explaining how to properly assemble the filter. This is why I always recommend doing thorough research before purchasing a filter, as it can save you from potential damage and health hazards. Now, let's dive deeper into the difference between nominal and actual sizes. For example, you may see a 20x30x1 filter labeled on the packaging, but when you measure the filter, you will notice that the actual size is smaller than the nominal size. But what exactly does nominal size mean? It refers to the rounded number used on packaging labels for air filters and wood. If your filter does not have the actual dimensions listed on the outside, you can measure it yourself to ensure you are purchasing the correct size.
However, if you are unsure or uncomfortable with measuring your filter, you can always consult an HVAC professional for assistance. They can also install an external filter grille if your unit does not have a factory-installed one, allowing for a thicker filter to be used.