Re: Air filter Location?
There are 'return filter grilles' made for this very purpose. Be sure though, that if you are going to use this, that you have one at every return. If it is a single, central return, then no problem; you have one inlet and one filter. If you have returns throughout the house this may not be as practical.
I would have someone come out and look at the system and see how difficult it would be to install an "external filter rack." This is a filter compartment that is mounted outside the furnace that eliminates the need to access the furnace in order to change the filter. It can be incorporated into the sheet metal itself, or a separate cabinet can be installed. Many of the higher efficiency filtration systems utilize a separate cabinet that goes in the return ductwork anyway.
Just be sure that whatever return air there is on the system gets filtered on its way back to the furnace.
All the best, Irishmist
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