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Understanding the difference between nominal and actual air filter dimensions can make replacement shopping easier. The size printed on the package may not be exactly the same as the measured dimensions of the finished filter.
What Is a Nominal Filter Size?
The nominal size is a rounded or standardized size used to identify a filter. It is commonly used when searching for a replacement product.
For example, a filter may be labeled with a size such as 20x25x1.
What Is the Actual Size?
The actual size refers to the measured dimensions of the finished filter. These measurements may be slightly different from the nominal size.
When the filter compartment has limited space, actual dimensions can be particularly important.
Compare Both Measurements
When replacing a filter, compare the nominal size of the existing product with the replacement listing. If actual dimensions are provided, compare those measurements as well.
This is especially helpful when switching between manufacturers.
Check the Filter Compartment
The available space in the HVAC filter compartment should also be considered. A filter must fit securely without being forced into place.
Conclusion
Nominal and actual filter sizes are both useful when choosing a replacement. Checking both measurements can help shoppers find a filter that is more likely to fit the HVAC system correctly.