When it comes to air filters, size matters. The biggest concern when using an improperly sized air filter is that it may not effectively prevent dust from accumulating on the motors and blowers in your HVAC system. This can lead to costly repairs or replacements, so it's important to make sure you have the right size filter for your home. In short, yes, you can cut an air filter if you know what you're doing and if the filters you're using don't weaken too much from the cut.
No, you should not stack air filters to fit in a larger slot. Generally, a filter with a higher MERV rating will reduce airflow. However, there are many other factors at play, such as the size of the filter and the type of fan motor in your air conditioning system. Virtually any HVAC professional will tell you that thicker filters work better than common 1-inch oven filters.
Thicker filters, known as multimedia filters, are usually 4 to 5 inches thick compared to the ubiquitous 1-inch filters that can even be purchased at grocery stores. Typically, you'll see filters with a MERV lower than 4 in residential ovens, window-mounted air conditioning units, or as a pre-filter in commercial units that need multiple filters. When you change oven filters, the first thing to do is to know what size oven filter you have. But what if your oven's air filter compartment is only 3 inches thick? In that case, the 1-inch oven filter is the better choice compared to the 4-inch filter, however, a 3-inch thick air filter is the best choice.
The type of fan you have in your boiler or air conditioner will largely determine if there will be a reduction in airflow in the system. If your boiler has an air filter in the return vent, changing the filter is easy, since you can do it from inside your home. At the higher end of this range, such as the MERV 11 or 12, the filter will also capture larger bacteria, such as Legionella, providing additional medical protection later on. Ovens come in various sizes and configurations, meaning there's no one-size-fits-all filter.
The first (and easiest) way to find out the size of your oven filter is to check the size of your old air filter. You'll need to do this if your boiler is missing the air filter and you don't know what size the air filter is supposed to be. This ensures that you won't restrict the air flow through the boiler too much and that everything is running smoothly. So, if it fits your oven, then a 4-inch air filter is better than a 1-inch air filter for improving air quality.
Look for where the return duct connects to the boiler and there should be a plate that covers the slot through which the air cleaner enters. Although it sounds exhausting to dive into the world of air filters right after researching your air conditioner or oven purchase, it's very important to make sure you have the right one. These filters can block larger particles such as dust, pollen and carpet fibers but not many more. When it comes to choosing an oven filter for your home, make sure you get one that fits properly and has a high enough MERV rating for your needs.