Altering My Furnace Filter

[1990C4S]

My furnace uses an oddball filter, 20" x 25" x 4.375". Pleated filters are about $30 locally.

Any reason not to modify the furnace locator and switch to a 20" x 25" x 1"?

The smaller filters are about one quarter the price.

[cabmandone]

Yep you can put a rack in the filter housing that accepts 1" thick filters. I modified several to accept 1" filters because the homeowner was tired of the thicker filter and them being more difficult to source.

With the room you have I'd put in 2 channels for 2 1" filters. The first would be changed more frequently as a "pre filter" and the second could be changed every other time or whenever necessary.

[1990C4S]

Good idea, thanks.

[masraum]

I assume a 4" filter is better (higher flow for the same or better filtration) and presumably can go longer between filter changes due to having 4x the filter surface area than a 1" filter.

I've wondered about swapping for a 4" filter, and wish I'd done that in our old house.

You can buy filters on Amazon, so you may be able to save some money that way.

[billybek]

I wouldn't change it.
Find a filter supply company and buy them by the box. I buy my 2" 40% pleats from a filter supplier by the box and it lasts a few years.

People put in 1" high efficiency pleats and wonder why their furnace is cycling on the high limit and the heat exchanger is defective. High pressure drop and reduction in flow across the filter and it gets much worse as the filter loads to the point where air bypasses the filter. They load very quickly.

A 4" pleated filter should last a very long time unless you have very dusty conditions or a pack of wild dogs living in the house.

You might find a light fiberglass pad to put in front of your pleated filters as a pre-filter.

[bob deluke]

Had an electric air cleaner on the furnace for years. The mother board crapped out and I gutted it and installed a mirv 13 pleated 4” filter in its place.change it twice a year. Have an air purifier running during the day, as we have two dogs in the house. Air in the house seems fresher and cleaner. Wife says her dusting is less too. Got the filters on line that are an exact fit for the filter box housing.

[1990C4S]

Did someone say dog hair??

[masraum]

Originally Posted by 1990C4S

Did someone say dog hair??

That looks like a dog that's happy to be sitting in the snow. What a good lookin' pup!

Yeah, I'd think that you'd be much better off with the 4" than a 1". You'll be changing filters more frequently, so will the added work and cost of extra filters save you much?

[Zeke]

Much less restriction on a 4" filter of the same MERV. Same MERV, at 1" might strain your motor. Know what you are doing. Ntoe: if you have a 4" depth capacity, you can get a MERV 1 thru 4 in a 1" and then put a spacer in (could be the frame of an old filter with the element removed) and put in a 1" MERV 9 thru 12 behind it. You will replace the first one more often as it will catch all the big stuff. Now if you have a contaminated home with lots of fine dust, that will likely pass thru the 1st filter and get filtered out at the 2nd stage. At that rate you may be changing the filters together.

The point is there are ways to use filters that cost less money. At the very least I'd place a washable filter in front of a high efficiency filter just to protect it be being clogged by large dust fibers like those from carpet, etc. Wash that every week if necessary. Takes less than an hour to dry.

[techman1]

Was in the same situation, the old HoneyWell electric air cleaner that died. Ordered the filters in a two pack thru Amazon.
Change every 6 months. This is in central Florida, so good air flow is a necessity!

[red-beard]

I'm using MERV 13 from an on-line source for about $55 for a pair. The issue, the higher the MERV, the more often they need to be replaced. I'm replacing about every 2 months to deal with allergy issues for my wife.

Aerostar Home Max 20x25x5 MERV 13 Honeywell Replacement Pleated Air Filter, Made in the USA, Captures Virus Particles, (Actual Size: 20"x24 3/4"x4 3/8"), 2-Pack, White

[rwest]

On my iPad, so can’t imbed this video, but it is from Project Farm and he tested furnace filters. I watched it a few weeks ago and if memory serves, the 4” filters hardly showed any airflow restriction.

You probably can go much longer on filter changes making the price similar.

https://m.youtube.com/watch?v=RkjRKIRva58

[cabmandone]

Check out filterbuy dot com (don't know if PP will allow if I type it normal). I bought 4 merv 11 filters for my spaceguard 20x25x6 for $117.

[rfuerst911sc]

Scan Amazon you can find decent filters for a good price . My fancy smancy 18 SEER dual fuel setup installed last year takes a 4" filter . In a pinch I installed four 1" filters .......... that was not good . Too restrictive but it bought me time to order online . Now my min/max reorder point is order more when I install the last I have on hand . I am using a MERV 10 or 12 can't remember which at the moment .

[cabmandone]

https://filterbuy.com/air-filters/20x25x4/

Here ya go. $16.54 each.

[1990C4S]

Plus $65 shipping to me...

I'm going to suck it up and pay, no alterations are forthcoming.

[cabmandone]

Originally Posted by 1990C4S

Plus $65 shipping to me...

I'm going to suck it up and pay, no alterations are forthcoming.

OOF!

Technically that's like $15USD shipping.

Honestly though, I wouldn't hesitate to modify your current system to hold a 1" that's easier to source.

[cabmandone]

Remember, It's all about air movement and cubic feet per minute moved. As long as the CFM is sufficient to move enough air across the heat exchanger to keep the heat exchanger from getting too hot and opening the limit switch, you should have no issues.

[1990C4S]

Originally Posted by cabmando

OOF!

Technically that's like $15USD shipping.

Honestly though, I wouldn't hesitate to modify your current system to hold a 1" that's easier to source.

They don't appear to ship outside the US, so that's $15 to my son's house, then north across the border...

[cabmandone]

Contraband!

If you meet somewhere in New Hampshire he can just hand it across the border... or so I've been told.