Locate the interior air-conditioning unit. Typically, it's located in an attic, basement, laundry room or small closet.
Access the interior unit's blower compartment. Up-flow air-conditioning units place the blower compartment at the unit's base, whereas down flow air-conditioning units locate the blower compartment at the unit's top.
Open the blower compartment by removing the protective screws with a screwdriver.
Pull the old filter from the indoor unit. Push the new electrostatic filter into the same position. Verify that the new filter fits exactly like the previous filter within the blower compartment.
Replace the blower compartment cover and reattach the screws with a screwdriver.
Turn on the Trane XL 1200 and test all functions. Whereas the positive effects of the filter may not be readily discernable, there should be noticeable improvements, such as less dust accumulating near vents and increased air quality, especially for those who are allergic to airborne particles, pollen, mold spores and the like.