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StringedInstruments
Auburn Fan
Member since Oct 2013
9216 posts

HVAC Filters - Thick or thin better for blower?
I just moved into a new house and it seems to have a dust problem. The return vents are individual to each room and after listening to my wife sneeze a hundred times a day, I decided to open them up for cleaning. They were atrocious with a thick layer of fluffy dust in every one. I vacuumed them as best I could but fear a little about the state of the ducts.

The system runs through a horizontal air supplier in the crawl space. I went to check the status of the filter and it looks like it hasn't been changed in years. It's a 20x25x1 MERV 7 that's a bit crumpled. It fits into a small slot but the entire space for the filter could accommodate a thicker filter.

I'm thinking about going with a 20x25x4 MERV 13 since the supplier is in the crawl space and the house already has dust issues.

I don't know the specs of the system but the house is about 2500 square feet.



tigerfoot
Pittsburgh Fan
Alexandria
Member since Sep 2006
33329 posts

re: HVAC Filters - Thick or thin better for blower?
off subject, but where is the thermostat?

Why not check into a duct cleaning service? To my knowledge you can put too much pressure on your system by going way up on your filter rating, reducing airflow and hurting your air quality. But, I am also pretty ignorant


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13
Scooba
LSU Fan
Member since Jun 2013
15779 posts

re: HVAC Filters - Thick or thin better for blower?
From experience, the thicker ones blow the best.


MaleB
NC
Member since Jul 2016
82 posts

re: HVAC Filters - Thick or thin better for blower?
If it's just for blowing, the thicker ones try harder


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120
diat150
Tulane Fan
OPELOUSAS
Member since Jun 2005
28055 posts

re: HVAC Filters - Thick or thin better for blower?
First, if it has this much dust your coils are probably caked full of dust and mold. I would get that checked out.


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10
bamarep
Alabama Fan
Monkey Town
Member since Nov 2013
35397 posts

re: HVAC Filters - Thick or thin better for blower?
Merv 13 is a good filter.


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01
tigeraddict
LSU Fan
Baton Rouge
Member since Mar 2007
6480 posts

re: HVAC Filters - Thick or thin better for blower?
Unit may not be able to handle a 4" pleated filter. Filters add a lot of static pressure drop. The supply fan must be sized correctly to overcome the pressure drop at the coin, filter, grills and the duct work.

You can try a 4" pleated filter, but i doubt the unit can handle it. My recommendations is replace the filter more often for the next few month as a clean filter is more effective than a dirty filter. i would also look at the evaporator coil in the unit to see if it is dirty, and if so, clean it as well.





Perrydawg
Georgia Fan
Middle Ga Area
Member since Jan 2014
2562 posts

re: HVAC Filters - Thick or thin better for blower?
I have been told and based on limited research that unless you have a high efficiency system, the basic or cheap filters from Lowes or similar are your best bet as the more expensive ones can cause issue due to restricted air flow.


StringedInstruments
Auburn Fan
Member since Oct 2013
9216 posts

re: HVAC Filters - Thick or thin better for blower?
Is the evaporator coil easy to access and clean? Any special equipment to use?

And I've read that a thicker filter can actually be easier on the air flow than a thinner one because thin filters are more dense than the thick ones. Further, once the thin filter gets clogged, it's going to block air flow whereas a thick one will have more breathing room to the extended surface area.


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11
statman34
Houston Astros Fan
Member since Feb 2011
894 posts

re: HVAC Filters - Thick or thin better for blower?
I agree. I used to use expensive filters but found that they did indeed restrict airflow. I now use the cheap ones and find my a/c works much better.


Spankum
LSU Fan
Miss-sippi
Member since Jan 2007
46999 posts

re: HVAC Filters - Thick or thin better for blower?
that sounds kind of odd....I am not sure why there would be that much dust in the ductwork. I generally buy some mid-grade filter and change it regularly (which I think is the most important thing). you may want to have someone come in and clean the ductwork up to give you a fresh start in your new house.

ETA: to answer your original question, heavier filters more effectively filter the air, but also provide more resistance to airflow. you have to find a filter that provides both filtration while still allowing decent airflow across the coil.
This post was edited on 7/7 at 9:17 am


MardiGrasTexan
LSU Fan
Grapevine, Texas..from Baton Rouge
Member since Sep 2005
3576 posts

re: HVAC Filters - Thick or thin better for blower?
My recommendations:

Without knowing the specs on the air handler/furnace, I would suggest not going any thicker than a 2" MERV8 on your system. Also,your evaporator coil is filthy and needs cleaning. I'd suggest using an a/c company versus using a duct cleaning company. An a/c company will properly clean both the indoor and outdoor coils and many do duct cleaning, too. They can also make sure your system is operating properly. Don't tell them you're having a problem with your a/c system or you will pay the ultimate price. Just call around and ask for estimates on a complete cleaning.

In the meantime, tell your wife to purchase some Flonase SensiMist. You can thank me later for that one.


MardiGrasTexan
LSU Fan
Grapevine, Texas..from Baton Rouge
Member since Sep 2005
3576 posts

re: HVAC Filters - Thick or thin better for blower?
quote:

I am not sure why there would be that much dust in the ductwork.


Because of the loss of air flow (dirty filter and coil),the airflow is restricted and slows down. The dust has no where to go, will swirl around in the return ducts and will build up in the ducts.


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10
MardiGrasTexan
LSU Fan
Grapevine, Texas..from Baton Rouge
Member since Sep 2005
3576 posts

re: HVAC Filters - Thick or thin better for blower?
quote:

I now use the cheap ones and find my a/c works much better.


You should use a better filter and change it monthly. Most people don't understand air "conditioning". Air conditioning is adding or removing heat from a space. It's also about air quality....dust, humidity, etc. You may believe it's working better but your house is probably quite a bit dustier using the cheap throw-away filter. This dust (which is rather gross when you know what's in it) is also in the air you breathe.


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11
14&Counting
Southern Cal Fan
Manhattan Beach, CA
Member since Jul 2012
15913 posts

re: HVAC Filters - Thick or thin better for blower?
quote:

I agree. I used to use expensive filters but found that they did indeed restrict airflow. I now use the cheap ones and find my a/c works much better.


This...go to Lowes, get a pack of cheap filters, and replace once a month


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BeerMoney
LSU Fan
Baton Rouge
Member since Jul 2012
4552 posts

re: HVAC Filters - Thick or thin better for blower?
I'm no expert but I believe you're supposed to use a MERV rating your unit is rated for otherwise you might damage the unit. So a 13 could hurt you. Hopefully some expert says yay or nay on that. Google that shite yo.


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brew400
LSU Fan
West side Best side
Member since Sep 2009
473 posts

re: HVAC Filters - Thick or thin better for blower?
I work on ac's from time to time. Get the cheapest finerglass filter you can find on amazon or lowes. Second get a stand alone air purifier and set it up in the living room, it will clean the biggest mass of air in the house and circulate to the other parts using the ac. The air condition is not meant to clean your air, only condition it.


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Duke
USA Fan
Gonzales, La
Member since Jan 2008
25949 posts

re: HVAC Filters - Thick or thin better for blower?
quote:

Also,your evaporator coil is filthy and needs cleaning.


This.

Not only are you impacting the airflow, you're limiting the heat transfer. AC has to run harder and longer to cool the house.


StringedInstruments
Auburn Fan
Member since Oct 2013
9216 posts

re: HVAC Filters - Thick or thin better for blower?
Just replaced the filter. Went with the one inch since I already had it but will check soon on its dirt level and then check the serial number on the unit to see if it can handle a thicker filter.

I peaked into the blower/furnace and it's fricking disgusting. Looks like a grey haired Wookiee got shoved inside. Unfortunately this is a rental home and we've already requested a bunch of needed repairs. Not sure how the landlord is going to respond if I insist on the furnace being cleaned especially when considering the fact that this guy hasn't thought twice about it being an issue.

I watched some YouTube videos on cleaning the evaporator coil and I could definitely do it myself if it wasn't in the crawlspace. I had to replace the filter nearly on my belly because of the tight fit between the floor and the ground. I didn't feel comfortable dealing with those parts while in that position.

I've also noticed the inside of the house has a "crawl space" smell. So thats great too! /S


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