Previously, I used a MERV 8-10 Filter / kind of mid range.
Today I cleaned the cold-air returns (as best I could).
Before cleaning, I installed the Filtrete 1900 / to better collect any dirt I loosened up.
It collected quite abit of dirt.
Now the question is "how long can I use this filter, before the differential pressure is to great?
I installed an Inclined Manometer
to show me exactly the pressure difference.
To me, using a Manometer (differential pressure gage) is essential in not over-working the blower motor.
Any filter, any MERV, any thickness, .... I read the gage / other then that, you're guessing how long to use the filter
The furnace manufacturer shows .50 inch max. of water column.
I plan on using any filter to a max of .40"wc
/ gives me a little wiggle room.
When I installed the Filtrete 1900, the gage showed .27"wc
The less restrictive filters (1085) have a 'higher' gage reading of .30"wc
WHY? .... because the 1900 filter has 48 pleats, vs 19 pleats / it's a bigger filter.
NOW, .... the question is, "how long will the filter last till the gage reads .40"
Ideal situation for me is the 1900 lasts 8-9 Months.
If only 2 Months, I would have to use a less restrictive filter, or have my furnace reworked to fit a 5" thick filter.
Another important thing to do is, clean your floors (more often) so the cold air returns are not sucking up excess dust.
I do not believe in using the furnace filter as an air cleaner, but I also don't want all that dust in the duct work.
Photo of my Differential Gages.
I like the 'red' liquid one most / dial one is for double checking, if needed
View attachment 91485
If anyone wants to buy the liquid Manometer, they are expensive, like $500.
I was lucky to get one on E-Bay for way cheaper.
View attachment 91487