When it comes to purchasing air filters, it is essential to understand how to measure them correctly. Most air filters are sold based on their nominal dimensions, so you should order the filter by its nominal size rather than its actual size. For example, a popular oven filter size is 20 x 25 x 1 inch, but its actual size is 19.5 x 24.25 x 0.75 inches. It is important that the oven filter fits securely, but there should be no need to force it into position.
If you have to force the filter into its slot, it is likely too big and can cause damage to the filter or reduce its ability to function properly. The filters are smaller than their slot to allow for easy replacement. In some cases, you may need a filter with unique or unusual dimensions and will need to order a custom filter. The oven filter should fit snugly but comfortably into the oven without having to bend or force it into place.
The actual size of the filter is the actual dimensions of the filter by length, width and thickness. Using old air filters can lead to high utility bills, costly damage and repairs, and poor home comfort. If you live in an older home with a non-standard size air return frame, you can use foam weatherstrip tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. When buying a filter online, the actual size will appear in the product list or product description.
For HVAC ventilation grilles located on roofs, a slightly larger filter size can be used to prevent it from falling out when the vent is opened. To ensure that you purchase the correct size for your system, you should measure the inside dimensions of the air cleaner inlet. Dense filters tend to get covered in dust and dirt more quickly and can clog faster than filters with a lower MERV rating. When an overly dense filter is used in an HVAC system that does not require that degree of resistance, it can restrict necessary airflow and cause the oven to work harder.
Although there are general timelines for when you should change your oven filter, there are some clear indicators that will let you know when it has become too clogged. Knowing the environmental factors in your home and neighborhood that can affect your oven filter will help you determine how often you should change filters. For common brands of HVAC systems such as Goodman, Lennox, Trane, Rheem York, Coleman and Carrier, most standard air filter sizes will work. It is important to make sure that you purchase the correct size for your system as either error can be quite costly due to having to send back wrong filters.