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  1. #1

    Cool evap coil 1/2 ton larger then condenser?

    Word has it in my shop that upsizing the evap coil will give you maximum dehumidification.

    I am a commercial service tech, I am not a res. installer so.....


    Question for you is: a 3 ton evap coil with txv going to work with a 2.5 ton 13 seer condenser?

    I spoke to the mfg. and they said you dont need a txv with a 13 seer only the 14 seer. I thought all 13 seers required txv for maximum eff. ???

    Now I am asking this question looking for real answers so for those of you who enjoy bashing people (you know who you are) please keep your comments to yourself.

    Thanks..........

  2. #2
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    See thread 84031 and udarrell web.

  3. #3
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    Upsizing the evap coil sometimes lowers latent capacity (so it wouldn't give you maximum dehumidification--downsizing the coil would, but you'd have to make sure it's rated by the manufacturer), but it's done to get higher efficiencies in most cases (for residential). It may depend on the manufacturer. There are some ARI matchups with 1/2 ton or even 1 ton upsize on evap coil. Hope this helps.

  4. #4
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    One of the nice ones will be along sometime.
    Last edited by beenthere; 06-23-2008 at 08:47 AM. Reason: retype
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  5. #5
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    Quote Originally Posted by beenthere View Post
    Wow.
    If you want to keep that attitude. i won't tell you the real answer, and how to size the ID coil for better humidity removal, and highest efficiency.
    Be nice to beenthere. He's got a lot of experience and a large wealth of knowledge regarding HVAC.

    Some, if not all manufacturers have performance data that provides the SHR and latent/sensible capacity of different coil matchups.

  6. #6
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    In terms of there in the user handle beenthere. I thinks it's a safe assumption there = everywhere.

  7. #7
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    Quote Originally Posted by beenthere View Post
    One of the nice ones will be along sometime.
    My back pain has me in a not nice state.

    I'm just waiting for someone to happen along and argue that the larger coil increases humidity removal due to the larger surface area.....so I can rip out their spleen.
    If more government is the answer, then it's a really stupid question.

  8. #8
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    Aug 2006
    Location
    Houston, Texas
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    Smile

    I went on a call the other day and the complaint was the upstairs system was not cooling as well as the old unit did.
    It was a new install and i could not get more than 12 degrees split
    I checked and re-checked everything and even charged the system with new refrigerant 410A, I still couldnt get more than a 12 degree split

    I got tired of the homeowner looking over my shoulder so i gave him a bucket of pukkie and made him seal his return chase
    TXV was good, static pressure was fine on both ends
    This was a Amana ASX14O301AB condensor with the factory matched 3 ton evap coil
    The coil was huge and I ended up replacing the condensor with a ASX140361AB and BAM welcomed a 18 degree split
    The homeowner had puckkie all over his ass when he emerged from his return chase...
    I was so happy i popped a wheelie on the way home
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  9. #9
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    Quote Originally Posted by mark beiser View Post

    I'm just waiting for someone to happen along and argue that the larger coil increases humidity removal due to the larger surface area.
    That myth has been around for longer then I can remember.

    Of course, these days my memory isn't as long as it used to be.
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  10. #10
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    Quote Originally Posted by fitterchick View Post
    Word has it in my shop that upsizing the evap coil will give you maximum dehumidification.
    Question for you is: a 3 ton evap coil with txv going to work with a 2.5 ton 13 seer condenser?
    I spoke to the mfg. and they said you dont need a txv with a 13 seer only the 14 seer. I thought all 13 seers required txv for maximum eff. ???

    Now I am asking this question looking for real answers so for those of you who enjoy bashing people (you know who you are) please keep your comments to yourself.

    Thanks..........
    If you are unable to fine tune the air flow over the coil, smaller coils remove a higher latent ratio because they are colder-less eff.-slower cooling. If you can fine tune air flow and can handle very cold air without getting condensation on the ducts, larger coils remove more moisture. Mainly because you can get the air colder without freezing. The negative of large coils is much more moisture retention to evaporate back to the structure during the off cycle. Most are better off not messing with this. The modern a/c has a larger coil with a smaller compressor. The current two speed a/cs use low speed on the entire coil. How good does that work? OK
    Real humidity control is supplemental dehumidification for low/no cooling load conditions. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  11. #11
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    A former member of this board used much smaller rated coils with condensers to remove more humidity.
    The larger coils couldn't have the air slowed enough to to remove as much moisture.
    Even though the sensible drops with lower air flow, it doesn't drop enough, and the stat is satisfied too soon.
    The smaller coil with lower air flow already having a lower sensible heat capacity will still remove more moisture because of the lower run time required to drop teh temp to stat set point.

    You can't apply the same pricipals of a decicated dehumidifier (where a larger coil may be better)to an A/C that also has to remove sensible heat.
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  12. #12
    Quote Originally Posted by teddy bear View Post
    The negative of large coils is much more moisture retention to evaporate back to the structure during the off cycle. TB
    can you explain that.......structure meaning plenum or evap coil?

    Sorry

    I would like to thank everyone with their replys, my service manager has been upsizing the evaps for a while and everytime I have asked why he tells be its for better eff. and dehumidification, I am glad to here other peoples point of views.

  13. #13
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    What ever brand your company installs.

    Gather up some of the model numbers of the condensers and coils you have been putting in.
    Go to the ARI website, enter those numbers and pull up the efficiency rating for those matches. And then look what the rating is for a smaller coil.

    If you can get the spec/technical guide for your brand, look at the ratings of the various matches. It should have efficiency ratings, and give you the TC, and SC of the match.

    You'll find that some 1/2 ton bigger match ups don't get more then a .5 SEER increase if that, and will have a lower latent capacity. With that lower latent capacity, some people turn their stats lower, so they use more electric then if a smaller coil was used.

    Structure, in Teddy's reference, would be the house, or building that the system is installed in.
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