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  1. #1
    Join Date
    Nov 2008
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    2 piece installs for coil/air handler or coil/furnace?

    Ok so i like to read instructions on installs even though i have done so many they are normal for me but of late with smaller furnace/modular blower being engineered and the large azz coils we are forced to think hard on how to install them together with limited space and cost etc..


    So normally on most brands we can get a coil to match the furnace/air handle either perfectly or the coil comes with a 3-4inch block off plate to cover the offset. Int hose situations all seems ok and havent come accross any issues.

    So the issues come when you read install instructions especially with gas furnaces and it specifically states that IF the coil is so much larger the the furnace you need to center the furnace to the coil and NOT to attach directly to furnace..

    So interpret that as needing a transition to the coil but my issue is IF we are shortening furnaces and shrinking footprints to fit closet and access holes this isnt possible many times and can be cost prohibitive to customers.

    why is the single block off plate ok but not when its a larger offset?

    also when we are using the single block off plate We usually put it at the bottom thinking that where the pan is and its not effecting the force thought of air being installed like this so we flush the tops of coil and furnace and then block off bottome of coil with supplied plate..

    Now back on subject how are we suppose to transition a furnace to coil say where the coil is 5 to six inches bigger then furnace and 1. in a closet?, no way this can work well as it can make the vertical height 70 inches or so 2. in an attic there may not be room horizontally to do this as well.. seems counter productive to shrink equipment size but then require transitions.

    so what's the theory behind this and also whats the down side to not using the transitions?


  2. #2
    Join Date
    May 2000
    Indianapolis, IN, USA
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    If you block off a few inches on 1 side you can block off airflow over 1 cell of the HX causing it to fail prematurely. Only takes a few inches for a good tinman to make a transition.

  3. #3
    Join Date
    Mar 2011
    Galveston Texas
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    I've made transitions in as little as 3" for a vertical furnace and box coil, I've also done custom stuff for both slab and box coils that are located in an attic and the furnace is in a closet. For our typical horizontal attic job the transitions I make are 18" with a 4" rise.

  4. #4
    Join Date
    Aug 2011
    North West FL
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    I have had to rethink my approach on change outs these days. We have had to move the location of the AH, just because we could not fit the new equip through the opening. Takes some out of the box thinking sometimes.

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