DIY Home Improvement Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
My ac/heat system uses a 4 inch 20x25 filter. I was wondering if i could use a smaller filter or possibly two 2 inch filters. This would save me money on filters but I don't know if there would be any other problems.

Thank you and I really hope this isn't a stupid question!!
 

·
AKA HVACTECHFW
Joined
·
2,426 Posts
use a 4 inch.... they should last at least 6 months if not a year at a time.... DO NOT USE TWO 2" FILTERS! That would be too restrictive.
 

·
Super Moderator
Joined
·
39,516 Posts
As above, stay with the 4" media filter. it should last at least 6 months, were as 2" filters will only last about 1 month. Along with the 4" providing much better filtration, and air flow, keeping your heating and cooling bill lower.
 

·
Registered
Joined
·
3,630 Posts
1" filters cost less and do a fine job change those every month if you have pets and carpeting...$$$$ :thumbsup: 4" gives better air flow:huh: you can't even see thru them :no:how does air get thru them even new out of the box....Home Depot on the 1" use that extra money for gas.4" cost a ton and restrict the return air into the coil.cooling runs Hi fan speed heating runs Med Lo and or Lo so consider what that 4" does...
 

·
Super Moderator
Joined
·
39,516 Posts
1" filters cost less and do a fine job change those every month if you have pets and carpeting...$$$$ :thumbsup: 4" gives better air flow:huh: you can't even see thru them :no:how does air get thru them even new out of the box....Home Depot on the 1" use that extra money for gas.4" cost a ton and restrict the return air into the coil.cooling runs Hi fan speed heating runs Med Lo and or Lo so consider what that 4" does...
Many of the "good" 4" media filters only have a beginning PD of .13 to .17", a rock catcher filter(the see through fiberglass ones) have a beginning PD of .07", and don't catch much dust or dirt.

A MERV 8-1" filter has about as much(more depending on brand) of a PD as 4" media filter, and doesn't last as long (some almost need to be changed every 2 weeks), or allow as much air to flow through it freely.

Its the total filter surface area that allows the higher and longer air flow over the same MERV in a 1 or 2" thick filter.
 

·
AKA HVACTECHFW
Joined
·
2,426 Posts
1" filters cost less and do a fine job change those every month if you have pets and carpeting...$$$$ :thumbsup: 4" gives better air flow:huh: You can't even see thru them :no:how does air get thru them even new out of the box....home depot on the 1" use that extra money for gas.4" cost a ton and restrict the return air into the coil.cooling runs hi fan speed heating runs med lo and or lo so consider what that 4" does...
wrong!
 

·
Registered
Joined
·
6 Posts
i thought the thicker the filter the more restrictive the air flow. at least that's what my furnace installation book says. it said something to the effect that if i use a 4 inch filter to expect and airflow decrease of 7% and that if need be i can use a 1 inch instead. maybe i am reading that wrong.
 

·
AKA HVACTECHFW
Joined
·
2,426 Posts
you are thinking about it wrong. a 4" filter has pleats its not a mass that is 4" thick full. Think of the pleats as one long sheet and if you were to take the filter apart and stretch out the pleats it would be much longer than a 1" filter that was pleated if you stretched it out. Therefore it is going to be less restrictive because there is more material for the air to flow through. Trust us, most of us here are professionals. it may be more restrictive than a blue fiberglass filter, but those don't catch anything but dust bunnies and they tend to harm systems by allowing too much particulate into the system and plugging up the blower wheel and evap coil. Those types of filters are not good for hvac systems. Obviously your system was designed to be used with a 4" filter, that is what I would use.

You get the most bang for your buck. A decent 1" pleated filter costs around $8 (they typically only last 1 moth tops).....and lets say your 4" filter only lasts 6 months $8 x 6 months replacing your 1" filter every month= $48 A typical 4" filter from the hardware store is around $30. That's a $18 dollar difference.

Now lets do the same thing and figure the 4" last a whole year $8 x 12months = $96
and the 4" cost $30 thats now a $66 difference.
 

·
Registered
Joined
·
3,630 Posts
4" filters are overkill in residential i service commercial rooftops TRANE 75 ton rooftop units doing 20,000 cfms and they ***** about 2" pleated vs fiber glass with VAV applications...never saw 4" only on Liebert computer rooms:wink:.unless this guy is building space shuttles:laughing: in his living room its a waste of money.change a 1" fiberglass tops 2Xs in the cooling season hold it up to the light if you can see light then air willl pass...minimal restictions go flip those burgers and have a beer let it ride...go to HD buy 4 filters and your good into next year same time
 

·
AKA HVACTECHFW
Joined
·
2,426 Posts
4" filters are overkill in residential i service commercial rooftops TRANE 75 ton rooftop units doing 20,000 cfms and they ***** about 2" pleated vs fiber glass with VAV applications...never saw 4" only on Liebert computer rooms:wink:.unless this guy is building space shuttles:laughing: in his living room its a waste of money.change a 1" fiberglass tops 2Xs in the cooling season hold it up to the light if you can see light then air willl pass...minimal restictions go flip those burgers and have a beer let it ride...go to HD buy 4 filters and your good into next year same time
Please, if you dont have experience in Indoor air quality for residential, then stick to what you know, which is apparently commercial.
 

·
Registered
Joined
·
3,630 Posts
try putting 4" in this job and you would thrown off the roof by the building engineers and mall manager...the only reason you can sell it residential is they believe all your numbers as there driving home in bumper to bumper traffic breathing...these units have all 2" and are right off a major expressway in upstate new york and the units do 100% OA in the winter to maintain 55F discharge air ..you want to change 4" filters in the snow you better stick to your info lacking home owners and that awesome Light Commercial you work on:whistling2: this 2500tons of rooftop your seeing
 

·
Super Moderator
Joined
·
39,516 Posts
4" filters are overkill in residential i service commercial rooftops TRANE 75 ton rooftop units doing 20,000 cfms and they ***** about 2" pleated vs fiber glass with VAV applications...never saw 4" only on Liebert computer rooms:wink:.unless this guy is building space shuttles:laughing: in his living room its a waste of money.change a 1" fiberglass tops 2Xs in the cooling season hold it up to the light if you can see light then air willl pass...minimal restictions go flip those burgers and have a beer let it ride...go to HD buy 4 filters and your good into next year same time
Residentila IAQ often uses 4" and 5" media filters, and even HEPA filters. Can't compare commercial to residential.

While I can walk in a 80 ton commercal unit to chage those 2" filters, I have yet to se a residential unit that big.

I work on little 1.5 ton and 100 ton units. They are not the same when it comes to air filters.

Malls with 6000 plus tons often just use 1 or 2" thick rock catcher filters, because of all the fresh air they require. A good air filter would plug too quickly. And they would be changing them on a weekly basis and not get anything else done. So they allow most of the dirt to go through to the coils and then onto the people.
 
1 - 13 of 13 Posts
Top