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  1. #1
    Join Date
    Jan 2007
    Location
    Southern California
    Posts
    23

    Arrow Rheem Mod, Coil & Filter Match

    After several estimates, no Manual J or D calculations, and estimators who did not want to deal with the complications of my install, tight space and old ducts, I decided I would have to design my own spec system, and then put it back out for bid. So I purchased HVAC-Calc, and I’m now going through all the Rheem Design Specs (yes, I’m an Engineer).
    I’ve selected the Rheem RGFD-O9EZCM Upflow Modulating Furnace and the RARL-048JEZ AC Condenser (thanks for all the recommendations here). Now the challenges are figuring out how to shoehorn the new FAU and Coil to my 61” opening (with 19” Return Platform, original built-in with 2x4 and drywall.) I may tear it out to get the entire 80” opening.

    I sure would appreciate any of you pros with Rheem / Rudd experience chiming in with your opinions.

    Questions:
    1) With the 34” Rheem RGFD Furnace, I must now select the best Coil, the problem arises in the selection and associated transition to the existing 19” x 22” built-in Plenum. I will only have 1 – 12” available for the transition, depending on the Coil and Air Filter selected. I would prefer to go with the RCQD Coil (28" tall, 15.10 SEER), but would have only 1” to transition from the 19x22” Plenum to the 22x24.5” Coil, is this enough or will I have airflow, turbulence or noise problems? (the plenum is another 16” deep up into the ceiling cavity where it branches to three supplies).

    2) If the RCQD Coil will not work, I would have to go with the RCHL Coil (17 1/2" tall, 14.75 SEER) and then I may be able to get 12” to transition from the 19x22” Plenum to the 22x24.5” Coil. Again, will I have airflow, turbulence or noise problems? (Could I get away with say 4" or 8" for the transition?)

    3) Any other concerns using the RCQD Multiflex W Style Coils vs the taller RCQD Coils?

    4) I will go with the Aprilaire 2200/2400 or the Honeywell F200E Air Filter. If I leave 6” between it and the cement floor of the return box, drawing air from all four sides, will this be enough airflow space to avoid noise or Static Pressure issues? (I need to keep it this shallow to have enough room for the Coil).

    Thanks for the help and advice, SCR
    Last edited by SoCal Residence; 02-19-2007 at 03:54 PM.

  2. #2
    Join Date
    May 2004
    Posts
    1,462
    Quote Originally Posted by SoCal Residence View Post
    (yes, I’m an Engineer).
    That's all I needed to know I don't want anything to do with it.......LOL
    If all else fails....Try reading the directions!

    Tell it like it is and let the chips fall where they may.

    Any views or opinions stated here are strictly my own.


  3. #3
    Join Date
    Jan 2007
    Location
    Southern California
    Posts
    23
    Quote Originally Posted by plain spoken View Post
    That's all I needed to know I don't want anything to do with it.......LOL
    Hi Plain Spoken,
    Thanks for the LOL, I understand, it was apparent from the estimates I received so far, if they could not just slap in a replacement unit and go, they did not want to deal with someone asking questions, oh well, that's the cross we engineer's must bear, LOL. But next time you fly and the audio video equipment box under you seat works and does not burn up, you can thank engineers like me.

    Anyway, back to the design, waiting for the Rheem / Rudd pros for input.
    Regards, SCR
    Last edited by SoCal Residence; 02-19-2007 at 03:46 PM.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,599
    The RCQD will give you a slightly higher SEER as you found due to larger surface area. Besides being tall, it is slightly more restrictive though the ECM in the mod should overcome that just fine.

    The Multiflex coils are great. Very low static drop over the coil. A good tinman should have no trouble making transitions from the coil to the plenum.

  5. #5
    Join Date
    Jan 2007
    Location
    Southern California
    Posts
    23
    Quote Originally Posted by BaldLoonie View Post
    The RCQD will give you a slightly higher SEER as you found due to larger surface area. Besides being tall, it is slightly more restrictive though the ECM in the mod should overcome that just fine.

    The Multiflex coils are great. Very low static drop over the coil. A good tinman should have no trouble making transitions from the coil to the plenum.
    Hi BaldLoonie,
    Thanks for the information, I was hoping you would show up, I've read many of your posts and reviewed your website. Thats good to hear about the RCHL, what is the minimum number of inches you recommend for the transition? I will have to go from the 24.5" to the 19" Plenum.
    Best Regards, SCR

  6. #6
    Join Date
    May 2003
    Location
    chesterfield, michigan
    Posts
    93
    Just a word of thought...I always change the plenum and transition to tie into the existing duct, it makes for a cleaner look and for professional.

  7. #7
    Join Date
    Jan 2007
    Location
    Southern California
    Posts
    23
    Quote Originally Posted by Chuck 999 View Post
    Just a word of thought...I always change the plenum and transition to tie into the existing duct, it makes for a cleaner look and for professional.
    Hi Chuck,
    Thanks for the reply, I thought of requesting that on my bid, but the current plenum only has 1" of exposed sheet metal, the remaining 15" is above the drywall, which I want to avoid tearing out, if possible. There are three take offs from the plenum, one 9", which goes to the living room, only 10" to the register. The second is 9" to the remaining first floor rooms. The third is a 14" duct to the second floor.

    The 14" flex duct is squeezed in between the 16" floor joists on the way through a softit to the attic. I may need to replace that, I suspect it is contributing to the low airflow in the second floor rooms, that is why I need someone to run a Manual D calcs for me when I get the bids. HVAC-Calc says I need a 13" Flex for the second floor, so maybe I'll be okay with the variable speed fan in the RGFD, but I know I better get a static test done.
    Regards, SCR

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