What Happens When an Air Filter is Too Big?

Learn what happens when an air filter is too big from an expert's perspective with this SEO guide! Find out how incorrect sizing affects performance & more.

What Happens When an Air Filter is Too Big?

If the filter is too large, it won't fit into the filter slot and you won't be able to put the cover back on. This can cause dirty air to infiltrate inside the boiler (and into the home). Folding the filter makes the seal imperfect. Air will filter through and around the bend, bypassing the filter altogether.

This causes dirt and debris to accumulate on the fan, slows down airflow, degrades performance, lowers air quality and generally makes a big mess that you will have to pay to fix or clean it later. Using an incorrectly sized air filter won't necessarily damage your HVAC system, at least not immediately. However, it does have an impact. Using the wrong size reduces the efficiency of your heating and cooling system. This can add up quickly and become an apparent problem that you're likely to notice on your next utility bill.

To avoid this, please check the size of your existing air filter before purchasing a replacement one. If you buy a filter that is too large, it will not slide properly into the slot. If the filter is too small, it will not cover the entire space and may allow dust and dirt to pass through. If you are not sure what filter size you need, check the manufacturer's specifications or ask your HVAC technician for help choosing the right product. The filters of the oven must fit securely, but must not be forced into position.

If you have to force the filter into its groove, it's probably too big. Forcing an incorrect filter size on a filter can cause it to bend, damage the filter, or reduce its ability to function properly. Filters are smaller than their slot to allow easy replacement. Some HVAC units may require a filter with unique or unusual dimensions. In these cases, you need to order a custom filter.

You also don't want to fit a 1 air filter into a 2 slot because the air takes the path of least resistance and will flow around the filter rather than through it if it's not the right size. A purifier is also worth considering if your unit cannot handle a full HEPA filter and someone in your household has the possibility of having respiratory problems. We also recommend consulting your air conditioner's instruction manual or talking to your HVAC technician when the system is first installed to see which filter is best for your unit. While a good quality filter can do a lot for your HVAC system and your home, you should never underestimate the importance of HVAC maintenance. An air filter that is too large will not be able to trap allergens, but will allow them to enter the air.

If you can't find your size in the store or need a custom-made air filter, online sellers are probably the best option for you. Once you reach MERV ratings between 13 and 16, you'll be firmly in the range of medical-grade air filters. You can find the recommended filter size for your unit model here, in the table titled “Find your air conditioner and oven filter by make, model number and size. After Covid-19, many HVAC companies have been hard at work designing systems that can handle HEPA filters so that they can remove viruses and bacteria from the air as it circulates.

For example, there may be a 20x30x1 on your filter label, but if you measure the filter, you will see that the actual size is less than 20x30x1 Nominal air filter size. All filters act as sieves for contaminants that come from a variety of indoor and outdoor sources, including coal, gas, oil and other fuels, household cleaning products, and building materials such as damp or wet carpets, insulation, or pressed wood products. However, the larger surface area of pleated filters allows them to capture more particles than their non-pleated counterparts. Even with regular maintenance, leaving a dirty filter inside the air conditioner can cost you a penny in repair bills and even shorten the life of the unit.

Installing several air cleaners 1 in a slot of 2, for example, can cause costly damage to the air conditioning unit since residential furnaces are not equipped to withstand this level of airflow restriction. The easiest way to identify the size of your air conditioner filter is to remove the existing filter from its slot and examine the filter frame.