Furnace filters

So I was gonna replace my gas furnace filter today before the cold weather starts, or at least the cold night weather. But for the life of me I can't find any information on or about my gas furnace - except for the brand and the date of installation. Heck, even the filter is one of those freeform washable filters that doesn't have a cardboard border with the dimensions on it (basically just a rectangular mat of green fibers that is totally impregnated with dust and looks about a useful as a third tit). So I took it out and measured it - it comes out to be 14x27
So I go out looking for a filter for it and no one I know of sells anything even remotely like that size, 14x30 14x24 14x25 but not 14x27.
So anyway I have a Payne furnace installed in 1983, there is a wiring diagram on the inside of the filter cover and that give a model number of 397H or 375A but that's it. There's nothing on the outside of the furnace and nothing that I could see on the inside where the motor and burners sit.
So what's the story, the Payne homepage is about a useful as a 4th tit and I couldn't pull anything up about a 375 or 397.
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I'm no expert. But we had the same problem. My local hardware store sells the big fiber mat, though, so we just bought that and cut our own filter. We get about two filters out of the mat.
BUT, and I don't know if it makes any difference, there are a lot of loose fibers after you handle and cut that green stuff, so we always run the vacuum hose over it a couple of times before installing. Goodluck, tina Eigenvector wrote:

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On Sun, 10 Sep 2006 13:44:21 -0700, "Eigenvector"

Perhaps get the next size down standard filter and make a cardboard frame to fit from box cardboard.
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I would pick up a 16 x 25 and see how it fits it is possible it stretched and that made it longer and narrower!
Eigenvector wrote:

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Eigenvector wrote:

filters have a / installation with an angle of 20- 70 degrees others have a /\\ installation. Actually, the steeper the angle the more air flow and filtering surface. So, if you can put it in at an angle, a 14 x 30 should work. If it has to be flat just cut 3 inches off and tape the end with whatever type of tape you want to use.
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Eigenvector wrote:

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Yeah but the thing that bothers me is that NONE of the filter sites let you search by FURNACE - which would be more helpful.
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Eigenvector wrote:

should be a shade more than one of the numbers you found at Filters Now
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Thank you that's the best information I've managed to glean from here and alt.hvac.
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Well so I measured the rack size, 13x23" Not exactly what I had hoped for, but that's what the dimensions work out to.
So I decided to cram a 14x24 in there until I can figure something out. I tried a 12x24 and that was way too skinny, so skinny it wasn't wide enough to be held by the filter supports. I ought to take a pic of it, because I swear it should be 14x27 but there is a retaining loop that cuts into the filter rack.
I would have totally thought that residential furnace filters would be standard sizes.
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