At the beginning of each heating/cooling season, the system should be checked as follows:
Filters may be duct-mounted or installed in the cabinet. A filter is installed at the factory. Note that filter access door fits over access panel. Air will leak if the access panel is placed over the filter door.
Filters should be inspected monthly and must be cleaned or replaced when dirty to assure proper furnace operation.
To replace filter:
See the tables below for replacement filter sizes.
NOTE — To use one inch filter bend tabs up as illustrated in figure 32.
Supply Air Blower
Outdoor piping insulation should be inspected yearly for deterioration. If necessary, replace with same materials.
Source: MaintainX (Community Member)