Where is the filter on my Carrier 8000 model furnace/air conditioner? I keep changing the filter in the air return grill but do not know where or if there are more filters to be changed. The owners manuel is of no help. Thank-you.

May be 2, 1 directly under Coils, and 1 at intake.

Usually if there is a filter in the return air grill that is the only filter you will have. Two filters would cause too much air restriction so one is all that is used.

Our House had 2, sort of like a belt and suspenders?

Two separate filters at separate locations is not desirable. Read the manual for the proper static pressure of the system. Usually two filters will cause the unit to be out of the static pressure range for proper operation.

hvac1000, The House came with 2, years ago we had removed the one under the coils, and only change the one at the intake, thanks for the info.