Stacking two pleated filters is not recommended as it will increase static and negatively impact system performance. Instead, you should use a two-fold filter. Stacking two disposable filters may be fine for the system, but it is not necessary. In some cases, the air controller's intake grilles or ventilation grilles have a filter depth greater than one inch. One-inch air filters are the most common, so some homeowners may think it is okay to place one-inch air filters in a two-, three-, or four-inch air filter slot.
However, this is not recommended. Stacking one-inch filters creates multiple layers for air to pass through. With media filters, there is still a single filter layer, but it has much more surface area. No, you should not stack air filters to fit in a larger slot. Depending on the size of your home, you may have more or fewer entry holes, but in most homes, the central air system has two intake openings covered with an air filter.
Some systems that accept two-inch filters have rails that can be inserted to accept a one-inch filter without it twisting and air surrounding it or, worse, getting inside. If you live in a large enough house, condo, or apartment, you'll have several return ducts to effectively recirculate air throughout the house; after all, no one likes poorly ventilated rooms and irregular temperatures. This means that you have more than one air treatment filter and you are likely to have several return grilles, at least one for each duct system per HVAC system. This is the metal box that contains the fan, the fan motor, the condenser coil and the compressor, many of the crucial components of the air system that allow warm air to enter and cool it before it circulates around the house. Because air controller filters have more filter material because they are larger, they can collect and retain more dust, pollen and smoke before they need to be replaced.
Technically, both components can be referred to as “ventilation grilles” because both are places where air circulates in your home. This tip from a Houzz discussion forum is worth mentioning: If you see a return duct that can accommodate a two- or four-inch air filter but has several one-inch filters stacked on top of each other to fit the slot, get rid of this configuration immediately. These vents can come in a wide range of sizes but are generally larger than the vents that release air into the house (which are usually similar in size to a sheet of paper). The lifespan of filters varies so the number of times it is necessary to replace the air filters in the return duct compared to the air controller varies because they have different sizes. Understanding the parts of your central air system is important because it helps explain cases where multiple air filters are used in several places. The MERV air filter rating is a measure of how effective an air filter is at removing particles from the air.
Because there is more surface area, more air can pass through the system, putting significantly less pressure on the motor, compressor, coil and other components. The technical specifications say that the maximum air flow of 2000 CFM must have a quantity of two disposable air filters measuring 20 x 25 with a minimum area of 960 cubic inches.