Will increasing my furnace filter thickness hurt my Furnace?

Question

I just purchased a home and the unit calls for a 1" thick furnace filter. Would it be okay to modify the ducting to allow for a 2" thick pleated filter? I've got terrible indoor allergies and would like to increase the filter thickness but not at the expense of decreasing my furnaces life....Please let me know what you think...

Answer 1

No it will not. It will better the air quality in the home. I've installed 5" media filters in my home. These should be replaced twice a year. The 5'' Media filters can be found @ any wholesale heating supply vendor. The airflow is the issue that you are referring to in regards to the furnace. As long as proper airflow is maintained, the filter will no affect the life of the furnace. With a 1" filter, someone with allergies, should be cleaned or replaced monthly. The hepa filter is a very good filter with someone with allergies. They also sell those in a 1" size. Email me if you have any questions.

Answer 2

Good answer by Obsean.

I just wanted to add that 4" pleated may restrict less but filter as well as a 2" pleated. The 4" will have much more surface area.

But in most cases the filter location is part of the ductwork and not the unit so what fits is particular to the design of the house or the plenum. For instance those in a "V" shape over the furnace if the plenum is tall you can put in bigger and thicker (but not wider) filter with no problem and increase the area for the air to flow even more.

But it is possible to restrict air flow and overheat the furnace with some filters that are "tight" filtering but not enough surface area.

And testing is about the only way to know for certain the effect.

Good Luck.

Answer 3

A 2" pleated filter has more surface area than a 1" filter so it should be OK. Most residential duct systems suck because they are undersized. Pressure drop on added components is what kills air flow. The pressure drop on a thicker filter should be less because of the increased surface area. If you know the tonnage on your A/C system, multiply by 400 and that is your ideal cubic feet per minute (CFM). The filter may tell you the pressure drop for a given CFM. The lower the better. There are also 4" thick pleated filters that work awesome and have little pressure drop (way more surface area).

Just be careful if you put the 2" filter in. Check the airflow at a register with and without the filter and see if you can tell a big difference. If it seems like a big difference, just put a standard 2" filter in or go with the 4" pleated.

Also, older units have smaller blowers-newer equipment is installed with butt kicking blowers because manufacturers figured out that most house duct systems are undersized or poorly installed. I know from experience.

Answer 4

I don't think you have an issue.  Remember, always clean your filters more often that you think you should.

Answer 5

A pleated filter would be fine. It's 2" thick, but it's not going to restrict air flow. If you bundles two normal 1-inch filters, that would definitely cause a problem.