View Full Version : Merv 8 to Merv 11?...Homeowner Question
12-19-2007, 05:52 PM
My American Standard Freedom 80 furnace has been using AirBear filters (20x25x5) with a Merv 8 rating.
It is time for me to replace my filter and I see that there are some AirBear filters rated Merv 11.
Can I safely use the Merv 11 filter with my furnace? I would like to have the better filtration of the Merv 11 but I don't want to damage my furnace.
Thank you, BertB
12-19-2007, 05:57 PM
the higher the merv rating the small the particles it will capture are.. this one would get 1 to 3 microns in size... higher the number better at filtering it will be, some will also say they are more restrictive though i dunno how much it would be
12-19-2007, 06:27 PM
MERV 11 is more restrictive than MERV 8. You will require greater surface area to maintain your current air flow. The AirBear folks should have charts giving initial pressure drop at standard face velocities. Filter change out occurs at double the initial pressure drop. MERV 11 will have higher initial pd and reach changeout pd faster than a MERV 8 with the same surface area.
MERV 8 in a 5 inch thick (pleated) filter offers good filtration with high dust holding capacity. I use a 1" MERV 8 pleated filter in my system and am very satisfied. Your system is designed for a limited pressure drop. I would not put a MERV11 on the average residential system or my system.
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