The nominal size is the dimensions that are normally used to label the filter. These measurements are usually a rounded value above the actual size of the filter. To get an accurate measurement, it is best to measure it yourself. If the dimensions are too faded to read or there is no air filter in sight, it is time to take matters into your own hands.
As an expert in SEO, I can tell you that if your HVAC system uses a thicker filter (typically 4 to 5 inches and usually mounted on the air handler), it is likely to be specifically designed for medium-efficiency MERV filtration. Compared to the cheaper basic filters available, medium-efficiency MERV filters, such as the Nordic Pure MERV 12, can significantly reduce airborne dust, mold spores, pollen and even smoke, and doing so can help alleviate respiratory diseases, according to an NIH review. On the other hand, if the filter is too large, the frame will wrinkle, airflow will be restricted, and longevity will be compromised. When used in the real world, the air in your home is constantly recirculated through the ducts and passes through the filters each time, thus increasing the cumulative effect of the filters. All of them (and Owen) told us that MERV filters in this range restrict airflow to a greater extent than low MERV filters, as measured by the drop in air pressure created by the filters when they are installed.
In fact, if you have to force an air filter in or out, it's the wrong size, so standard sizes are usually half an inch smaller than advertised. What's worse, incorrectly sized air filters can overload your air conditioning system, damage it, and increase your energy bills. For example, the filter label may have a size of 20 x 30 x 1, but if you measure it, you'll see that the actual size is smaller than the nominal air filter size of 20 x 30 x 1.If that doesn't work, you may be able to find the proper dimensions of the air filter in your HVAC manual. In addition, if there is any resistance to airflow caused by using a filter that is not the correct size, it can cause unnecessary strain on the air conditioning unit itself, potentially damaging system equipment and increasing energy bills. Fibreglass, polyester, washable, pleated and electrostatic filters offer different air filtering capabilities. Getting an exact fit is crucial to having an effective air filter: the wrong size won't fit and will cause the filter to stop working properly.
Most people won't be able to find the size air filter they need at their local home improvement store.