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Filter Replacement Interval

369 Views 5 Replies 6 Participants Last post by  surferdude2
I have a 3-year-old Trane HVAC furnace and AC system for my house (tuned & cleaned yearly). When the filter is brand new the unit works great, and is appropriately sized for my home.

However, after about 3 months I find the unit will sometimes have hard a time keeping up during extreme cold (for North Texas) 20-30 degrees, or extreme hot 95+. The outside air vent is also set to lockout during those extreme temps, so no outside air is coming in the house.

Once I replace the filter, it will go back to working fine. I have tried both OEM Honeywell & 3M filters (Merv 11), and the 4" filters say they are supposed to last 12 months! My house is kept very clean - is this just marketing lies, or is there another reason these filters are only lasting me 3 months?

1 - 6 of 6 Posts
my thermostat tells me when to change,
but I have in the past done it like every 3 months
after 3 months you should see the filter, disgusting
and NO one in our hose smokes BTW
In the 37 years ours has been in service we've never had a filter problem or a dirty blower that needed cleaning with a fiberglass / hog hair electrostatic stacked. I believe we'll stay with what has worked by washing the filter, usually 4 times / year and replacing the fiberglass a couple times/year. Also maybe filters that measure 14x24 in two returns for a 2.5 ton unit has something going for it.


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Do you live in a dusty area?
How many people live in your house? Skin cells create a lot of indoor dust.
Do you have animals? Did a previous owner? I worked on a house where dog hair reduced a 6” duct to 2”.
Do you have carpet or hard flooring? When we got rid of all our carpeting we got more dust in the filter.
Can the fan be set to a higher speed? Perhaps your system is restrictive.
Do the filters look filthy? As they get dirty they filter better until they restrict too much.
Cooking fumes can kill a filter pretty fast. It depends on what kind of diet you have and how well your range hood works.

We have carpet in all rooms, including the full basement. We get plenty of the type of dust that carpeting produces but filters last 30 days and still look usable although I pitch them.
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