I have an American Standard high efficiency gas AUY060 furnace (60,000 BTU heating and variable speed DC motor).
I believe this is the same as the Trane TUY080.
I don't have any external filter box, and until now have been using the OEM washable filter inside the furnace. I just tried the 3M Filtrete "Micro Allegen" filter, which looks like it will clean the air a lot better.
Unfortunately 3M doesn't make the 17x25x1 size that this filter requires, but they do make a 16x25x1 which fortunately fits fine, thanks to the spring loaded filter holder.
Are these 3M filters too restrictive for the variable speed furnaces in the long term? I will be sure to keep up with inspecting/changing the filter once a month. What should I look for to ensure that the filter isn't making the blower work too hard?
I would consider an external filter, but due to the furnace location and the side/upflow configuration, the return duct would have to be rerouted and angled funny away from the furnace so that there would be room for an external box, and that isn't feasible in my case.
Also are there any better 1" filters than 3M Filtrete (more air flow for the filtering, better value, etc.
Thanks for any advice!