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  1. #14
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,005

    Lightbulb

    The 24x30 return is already there and unless I rip it out and alter the wall and the ductwork it remains the bottleneck so to speak. (when in second stage)
    Well, it's not in the high BTUH 2nd stage much...
    However; how difficult would it be to make another 24X30 (or 24X24) filter rack somewhere in the conditioned area?

    A lot depends on how much depth there is between the filter & the return area before entering a RA duct; we also need to know those factors.
    Is it a rectangular RA duct within the wall?
    The duct area could also be a problem...

    The two (2) RA Filter-Grilles would improve the filtering process & improve airflow efficiency.

    You wouldn't have to change filters as often, & it would really reduce the pressure-drop during the filter loading process...
    Last edited by udarrell; 08-07-2011 at 02:58 PM. Reason: two (2) RA Filter-Grilles

  2. #15
    Join Date
    Jul 2011
    Posts
    24
    Quote Originally Posted by udarrell View Post
    Well, it's not in the high BTUH 2nd stage much...
    However; how difficult would it be to make another 24X30 (or 24X24) filter rack somewhere in the conditioned area?

    A lot depends on how much depth there is between the filter & the return area before entering a RA duct; we also need to know those factors.
    Is it a rectangular RA duct within the wall?
    The duct area could also be a problem...

    The two (2) RA Filter-Grilles would improve the filtering process & improve airflow efficiency.

    You wouldn't have to change filters as often, & it would really reduce the pressure-drop during the filter loading process...
    Hi Udarrell,

    As far as the 1st stage vs the second stage my reasoning was based on the reduced cfm in the 1st stage which would be 1300cfm (1st stage) vs 1550cfm(second stage)

    I will get the dimensions of the connecting duct work to the return in a few min, and post accordingly.

  3. #16
    Join Date
    Jul 2011
    Posts
    24

    Return Duct connection(s) size

    I'll try to describe this the best I can.

    Starting at the units filter location...
    28"h x 28"w x18" long duct...then
    4' long 18" round flex...then
    Connects to (remnant of old return line) 32" x 1' x 6' long (another installer left the extra 6' to reduce oil canning possibility) then...
    that is attached directly to the vertical grill box which is 24" wide x 36" high and 20" deep.

    The grill box being 36" high internally includes the amount it goes thru the floor aprox. But the grill filter size is 24"x30".

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,311
    Adding a second return would be beneficial.
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  5. #18
    Join Date
    Jul 2011
    Posts
    24
    Udarrel and Beenthere,

    Adding a second return...

    That's something I'm going to have to see about, precisely where one would go.
    Of course not so much on what wall the grill would be as much as if there is enough space behind the wall for another return box.

    If I can find a location, I'm thinking that the second return line should start off of the box/duct attached to the unit itself which is 28 x28x18.
    Attaching after that would have the second return also going thru the 18" round flex which would seem to me to be creating another bottleneck.

    Something to think about...Thanks

  6. #19
    Join Date
    Jul 2011
    Posts
    24

    2 grill plenum?

    Ok, this might be a stupid question.
    I'm quite capable of them from time to time.

    The Plenum that the current 24x30 return grill is installed to is 24" wide 36" tall and 20" deep.

    It is installed in a somewhat useless small triangular closet (a remnant of the builder 30 yrs ago)

    Could another return grill (and filter) be located on the backside of the current plenum 'in the closet' and then replace the current 30" wide closet door with a louvered door? Or perhaps thru the wall vents from the closet.
    Exercise room (x-bedroom) and Hallway are adjacent.

    This would put both return vent intakes around the corner from each other with the t-stat in between.

    Modification of the current plenum in the closet is available. Possibly lengthening it taller for the additional grill/filter so they aren't back to back, if that's a problem.

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,311
    As long as the closet is only used as a utility room, and its not a gas or oil furnace.
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  8. #21
    Join Date
    Jul 2011
    Posts
    24
    Quote Originally Posted by beenthere View Post
    As long as the closet is only used as a utility room, and its not a gas or oil furnace.
    The closet (if you can call it that really) is a triangle 5' wide at the door and 8' in comes to a point. literally.
    Besides the Plenum there's vacuum cleaner and some obscure junk thrown in there.
    As long as the vacuum stays there will be peace in the house.

    So having 2 filters 24x30 on the same plenum of that size is ok?
    Plenum 24wx36hx20d.

    The heating system is a ground source heatpump in the basement right below that closet aprox.
    No oil or gas in the home at all.

  9. #22
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,311
    It is a code violation to use a closet as a return path. Since its used as a closet, the return grille can't be in it.
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  10. #23
    Join Date
    Jul 2011
    Posts
    24

    Update

    Ok I decided to get the 4" filter for now and the General Aire 4002 - G99
    Honeywell merv 10
    24" X 30" RETURN GRILL FILTER FC40R1177 4" pleated. NEW
    vs
    1" biosponge OLD

    I know this isn't terribly scientific but I installed the 'General Aire 4002 - G99'
    Put in the new 4" filter and set it up with the fan on it's highest setting.

    Then I removed the 4" filter and installed a 'new' 1" biosponge filter that I had been using previously.

    The new 1" biosponge showed as not only needing replacement but was over halfway thru the 'replace' section of the General Aire 4002 - G99.

    Apparently the 4" filter does allow 'way' more air flow, at least when it's new.

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