HVAC filters too tight


The air return for my HVAC is 14x24. I use 14x24 3M Filtrate filters. However, the fit is extremely tight, and I have to crush the cardboard filter somewhat to force fit it into the opening. It seems like the opening is 1/16" too small or of the filter is 1/16" too big. Is this a common problem? Are some brands of filters slightly smaller?
Best, Christopher
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I guess someone sometime bent the metal, maybe use a peice of wood to get it the right size
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I'm the original owner of this home that was built ten years ago. There are two 14x24 returns, and they are both undersized for the 14x24 3M filters. It appears the framing was constructed from a long piece of sheet metal.

I don't think I can make the hole bigger using wood and a malet because three of the corners are bends, so making the hole bigger would reguire "stretching" the lengths of sheet metal. I'm guesing the only solution (other than crushing the filter) would be to replace the current framing with new framing.
Best, Christopher
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If the hole is just too small, that would be your option. Before you do all that, take out the sheetmetalwork, and cut it in half at one corner. Reinstall with it tight in the two remaining corners, and just make it fit as tight as you can. Maybe use something like a screw jack in the opening to stretch it. You probably only need an eighth to a quarter inch.
Steve
visit my blog at http://cabgbypasssurgery.com watch for the book
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Yeah, I think that would work. Thanks for the suggestion.
Best, Christopher
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Try a scrap of wood and a hammer. You may be able to enlarge it a little.
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if wood doesnt work Vige Grips come in wide versions for metal holding while welding , I used to have a pair of 6" wide ones, most any big hardware store should have them but a peice of wood hammered right should fix it and maybe use pliers. you need the filter tight so no dirty air bypasses it.
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The answer is yes, no, absolutely, maybe, and I don't know.
I just had the same problem with some 20 x 25's. They fit two abreast. I got the medium grade ones, and they are a little flimsy. I turn on the air to get suction to hold them in place for placement. When I did that, the air sucked them inward so much it collapsed them. I had to run two wires along the middle edges to keep them from collapsing inward. Some of the filters fit great, others seem inconsistent in size.
But! One of the big deals is that the frame is held on with 1/4" head screws and the heads sticks out and contact the outer edge of the filter. Those types of fasteners are very common to HVAC sheet metal people. So, I removed them and put common drywall screws so that it would not stick out, and that they could be tightened a bit to suck that portion of the frame outward and make more room.
It could be the screws, maybe the opening is a little out of square, or just badly produced screens. I am going to have to do the wire thing with all my returns (four) so that as the filters age a little, and the pressure builds up, they are not sucked up. And that is made worse by any crimping in that flimsy outer cardboard frame.
I'd change those screws, and perhaps add a couple of wires for strength. But the wires MUST be far enough inside that they don't hold the face of the filter out.
HTH
Steve
visit my blog at http://cabgbypasssurgery.com watch for the book
A fool shows his annoyance at once, but a prudent man overlooks an insult.
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The returns do have the 1/4" head screws, but are recessed about 3/4" from the outer edge of the framing. The cardboard filters won't even clear the framing until they have been crushed a bit.
It's been ten years, but I think the original filters installed when the home was new were those cheap pieces of fiberglass cut to size and stuffed into the hole.
Best, Christopher
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Christopher Glaeser wrote:

I encountered the same problem with the Filtrete filters (16x25) a year or two ago. I had been using the same Filtretes for several years without a problem.
I believe 3M uses various sources for manufacturing the filters. The actual (not NOMINAL and not the "actual"-as-printed-on-the-filter) thickness of the filters changed. I measured an old one which had worked fine and a new one that was approx 1 mm thicker. Both the old and the new had an "actual" thickness of 2 cm. printed on the filter.
I spoke with a 3M customer service person who claimed he "checked with the lab" and there had been no change in specs and no reported problems. I told him all he had to do was measure the thickness and compare it to the specs printed on the filter itself.
I think many furnace installations have a lot of play in the filter frame; mine doesn't and it sounds like yours doesn't either -- which is great, as long as the filter manufacturers produce filters with actual dimensions as specified.
I stopped using Filtretes.
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Perhaps I should switch to reusables. I see some online that can be ordered with tolerances of 1/8". Any comments, opinions, or recommendations for reusables?
Best, Christopher
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Reusable filters are junk.....IMO
I buy "DP Max" filters from here http://www.airguard.com
12 for $50.00. (14x20)
Their filters are actually 1/2" smaller in length and width. So that would solve your problem. IOW, my 14x20's are actually 13 1/2x19 1/2.
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wrote:

Reusable filters are junk.....IMO
I buy "DP Max" filters from here http://www.airguard.com
12 for $50.00. (14x20)
Their filters are actually 1/2" smaller in length and width. So that would solve your problem. IOW, my 14x20's are actually 13 1/2x19 1/2.
Thanks for the link. I may try a pack on my rentals. They cost about what they do at the borg.
Steve
visit my blog at http://cabgbypasssurgery.com
A fool shows his annoyance at once, but a prudent man overlooks an insult.
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I have historically bought 3M products anytime they are available because o f their historical quality. I use the same filter and it actually is the s ame size. I have 4 of them in my house. The 3M Filtrate filters have alwa ys been too large. I use a putty knife to slip behind the filters to help work it into the opening sort of as you would use a shoe horn. I also have one 14 X 14 return vent and the Filterate filer is equally oversized for i t. I've tried different brands with mixed results. There is a difference in the exact sizes of filters from brand to brand. Some are too small whic h allows the filter to move around enough to even bang up and down on cei ling mounted filters as the HVAC cycles on and off. Very anoying. With s ome effort I have been able to get the 3M's in but they have to be forced a nd even a lot of care they have at least some distortion. Im not sure if a ny significant amount of air is getting buy unfiltered. The biggest issue is that my filters are 12 to 16 feet above floor height. 3M filters create a dangerous situation to have to work with both hands and get beside or ab ove them to get them in. We shouldn't have to set up scaffolding or deform our frames to change the filters because 3M cant keep their tolerances wit h an acceptable range. It also could be that 3M is trying to use the same f iler for metric and SAE filters.
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snipped-for-privacy@gmail.com posted for all of us...

of their historical quality. I use the same filter and it actually is the same size. I have 4 of them in my house. The 3M Filtrate filters have always been too large. I use a putty knife to slip behind the filters to help work it into the opening sort of as you would use a shoe horn. I also have one 14 X 14 return vent and the Filterate filer is equally oversized for it. I've tried different brands with mixed results. There is a difference in the exact sizes of filters from brand to brand. Some are too small which allows the filter to move around enough to even bang up and down on ceiling mounted filters as the HVAC cycles on and off. Very annoying. With some effort I have been able to get the 3M's in but they have to be forced and even a lot of care they have at least some distortion. Im not sure if any significant amount of air is getting buy unfiltered. The biggest issue is that my filters are 12 to 16 feet above floor height. 3M filters create a dangerous situation to have to work with both hands and get beside or above them to get them in. We shouldn't have to set up scaffolding or deform our frames to change the filters because 3M cant keep their tolerances with an acceptable range. It also could be that 3M is trying to use the same filer for metric and SAE filters.
Historically this means nothing to me.
--
Tekkie

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I used them for about four years. They are difficult to get clean. Very difficult. They are mostly expensive, some VERY expensive. The size micron particles they trap is not that small. You can put sprays on there like Lysol that help catch particles, and provide some degree of disinfectant, but I hate the smell of Lysol or similar products from diving days when we used it in our helmets and decompression chambers.
I like the midgrade waffle shaped ones with a lot of wire to keep them from caving in. The paper ones, not the snaky thread kind.
Steve
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