I have a Lennox G43UF furnace and I am not sure if I need to have both a filter for a side return and bottom return. If I do (which sounds logical), where would the location of the bottom return filter be? I just bought a home and there were no filters in place.
The manual for the filter states the following: "This unit is not equipped with a filter or rack. A field−provided filter is required for the unit to operate properly. Table 1 lists recommended filter sizes. A filter must be in place whenever the unit is operating."
Table 1 per above lists the size of filter that I would need for side return (16x25) and bottom return (20x25).
I have located the side return filter which seems to be behind the tin foil in image 1 (in centre of picture) but I have no clue where the bottom return filter would go.
Any advice would be appreciated!