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Thread: 1978 Rheem

  1. #1
    Join Date
    Jul 2005


    I guess I should feel lucky that this 1978 Rheem furnace actaully got a 1 year certification after it's inspection last summer. But now, I need to replace the filter and I can't tell what size I need. I tried to measure the filter area and came up with 22 x 16.5 inches. Doesn't seem to be a standard size. Oh, I should mention that the filter the previous owner had in there looks like an adjustable plastic frame with a cut -to-fit filter.

    Does anyone know if I will ever find a standard filter to throw in this furnace, or if I need to go the custom fit route?

  2. #2
    Join Date
    Aug 2003
    Fort Worth, TX
    Is the entire 16.5 x 22 opening free area, or is there a sheetmetal lip or flange that might reduce the actual opening to 16 x 20 (a very common filter size)? Even so, there should be a retainer device of sorts to prevent the filter being sucked up into the blower when the blower door is closed. If a 16 x 20 filter will cover the free area below the blower wheel without any gaps and can be retained by a clip or other device, you should be good to go with this filter size.

    Your other option would be to have a filter grill installed adjacent to the furnace (in the wall, for example) with a sealed return to the furnace (stud cavites can draw air from non conditioned spaces if they are not sealed) and a standard filter size (such as 20 x 20) can be used in this grill.

    Don't do this if the grill will draw the same air the furnace uses for combustion, such as in a basement.

    [Edited by shophound on 07-10-2005 at 07:20 PM]
    Building Physics Rule #1: Hot flows to cold.

    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure

    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  3. #3
    Join Date
    Nov 2004
    Originally posted by gav76
    Does anyone know if I will ever find a standard filter to throw in this furnace, or if I need to go the custom fit route?
    Yea man,you might need to go the custom fit route.Easiest
    way is to use the adjustable frame.Go to a supply store(look it up in the phone book)and ask for cut to fit filters.They are available.

    Change your filter often!

  4. #4
    Join Date
    Jul 2005
    Thanks guys. I had tried to measure the actual filter space (so, inside teh flanges, not just the rough opening.

    I just bought an adjustable frame filter, but I had to drill holes to get a good fit.

    I went to install it, and the frame itself is too wide to fit in the recess flange. So the thing just flops against the squirrel cage. I think I am going to adjust the frame open a little more and duct tape the dang thing in place.

    I really don't see this furnace lasting too much longer anyway.

    Thanks again.

  5. #5
    Join Date
    Jul 2005


    Thats what we call a field transition!! Thats using your head gav.

  6. #6
    Join Date
    Apr 2004
    When the furnace is replaced, make sure your furnace installer installs a good filter rack outside the unit. I dont think opening and closing the blower door regularly is a wise move for a home owner. In an upflow, you have to take the top door off, then the bottom and fight with a wire when some forthought by the original guy would have made life alot easier.

    Darn that reminds me, I still need to go clean mine, its been a few months, I keep forgetting.

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