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  1. #1
    Join Date
    Jul 2008
    Posts
    11

    Slab Coil vs "A" Coil

    What is the difference between a slab coil and an "A" coil of the same size/capacity and what the benefits of either?

    We are in the process of replacing our upstairs AC with a new condenser and coil. Most installers have quoted A coils (which we have now), the last quoted Slab coils saying they were better, but not really giving me a reason.

    There is plenty of space in the attic where the current coil

    Help is appreciated. I am trying to pick a system this weekend.

  2. #2
    Join Date
    Feb 2003
    Location
    garland, texas
    Posts
    680
    A slab coil is just a flat coil. For the last 30-40 years or more they were the coil most often used when furnace was in horizontal position, A coils were used in the upflow or downflow position. Slabs require a duct transition to adapt to usually smaller furnace opening which is an extra expense to someone. In the last 10 years manufactures have adapted the A for use in the horizontal position. It does not require a duct transition. Coil style does not matter if the coil is matched to the condenser.

  3. #3
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    Slab coils give better airflow performance than A coils because the pressure drop through them is significantly lower.
    My experience has been that they also tend to have fewer condensate disposal problems too.
    If more government is the answer, then it's a really stupid question.

  4. #4
    Join Date
    Jul 2008
    Location
    Alabama
    Posts
    658
    Quote Originally Posted by mark beiser View Post
    Slab coils give better airflow performance than A coils because the pressure drop through them is significantly lower.
    My experience has been that they also tend to have fewer condensate disposal problems too.


    Yeah! They are easier to clean once you get through the transition too!

  5. #5
    Join Date
    Jul 2008
    Posts
    11
    So for a horizontal application sounds like you would all recommend a slab coil then?

  6. #6
    Join Date
    Feb 2003
    Location
    garland, texas
    Posts
    680
    We frequently see slabs retrofitted to existing furnaces and supply air plenums with a large majority of the surface area on both the entering and exiting sides of the coil blocked off because no transition was used and existing supply air plenum is smaller than coil opening. Use an appropriate length transition, new supply air plenum, and if cleaning the the coil in the future is a concern have an access door installed in the transition.(an access door is not foil tape over the flap of sheetmetal cut out to look at coil)

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