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  1. #1
    Join Date
    Apr 2008
    Posts
    8

    Carrier AC mismatch of Condensing unit and Evaporator coils

    Hi,everyone

    I get a question about the size mismatch of Condensing unit and Evaporator coils for Carrier AC. After consulting several parties, including the factory certified dealers, Carrier corporate, I am a little confused now. Here is my story

    I am building a 2 story, 3200sqft house (facing south) in west Houston by Meritage Homes. Here is my HVAC setup (from my house inspection report)

    FURNACE SYSTEM:

    System: Lower # 1
    Furnace unit Carrier
    Model # 58STA090
    88,000 BTU Input
    The energy source for this unit is natural gas.

    System: Upper # 2
    Furnace unit Carrier
    Model # 58STA070
    66,000 BTU Input
    The energy source for this unit is natural gas.

    AC_SYSTEM:

    System: Lower # 1
    Condensing unit Carrier
    Model # 24ABA448A320
    The energy source for this unit is 240 volt electrical
    Evaporator coils unit Carrier
    Model # CNPHP6024ATAABAA

    System: Upper # 2
    Condensing unit Carrier
    Model # 24ABA436310
    The energy source for this unit is 240 volt electrical
    Evaporator coils unit Carrier
    Model # CNPHP3617ATAABAA Serial # 4607X38496

    The #1 system appears to be operational as indicated by the 67.2/48.9 temperature differential reading across the evaporator coils, which in this firm's opinion, is at a normal rate for the Houston area.

    The #2 system appears to be operational as indicated by the 66.7/46.9 temperature differential reading across the evaporator coils, which in this firm's opinion, is at a normal rate for the Houston area

    However, The # 1 system evaporator coils are not the same size as the condensing unit and is over sized by one ton (5 ton of evaporator coils Vs. 4 ton of condensing unit)

    As I talked with my coworkers and friends, the consensus is that usually evaporator coils should be equal or half ton bigger than condensing unit. I also looked up this forum, it seems there are still a lot of debates about this. I also called two Carrier factory certified dealers in west Houston, one who claimed he has been in the industry for 30 years, thinks it is OK to have one ton difference. The other dealer, a lady, said the two should be size match. I also called the Carrier customer service, the guy is not technical (the consumer has no access to the direct technical support from Carrier, except the commercial side or the dealers). After I provided all the model numbers for the system, he told me from the company internal document, having one ton bigger of evaporator coils than condensing unit is fine, and actually is more efficient for this two particular models match(condensing unit 24ABA448A320, evaporate coils CNPHP6024ATAABAA ). He would not provide any reasonings behind it. My house inspector (he is pretty experienced in house inspection for 30 years, but not HVAC
    trained and certified) called me this evening that after he talked with two friends in HVAC field, such size mismatch may be OK with the Carrier new AC system. His two friends have done similar work recently and it works well. Frankly, I am a little confused now and not sure whether to push the builder hard to replace the evaporate coils for the system #1 with 4 ton unit to get size match. The house is very close to the final closing now. Any advice will be highly appreciated, Thanks,

    BTW, our AC fans outside is a bit abnormally noisy. Any ways to fix it?

  2. #2
    Join Date
    May 2007
    Location
    Boise, Idaho
    Posts
    91
    If you are really worried about it remove the piston and replace it with a txv. Very smart devices!

  3. #3
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,113
    Quote Originally Posted by gqchen View Post
    BTW, our AC fans outside is a bit abnormally noisy. Any ways to fix it?

    Yea I have a good fix for that get them to remove those Carriers and install RUUD's and you
    won't have any problems period, and surly not a noise problem outside, matter fact you will
    have to listen hard to hear them...
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  4. #4
    Join Date
    Apr 2008
    Posts
    8
    Quote Originally Posted by Alantoy13 View Post
    If you are really worried about it remove the piston and replace it with a txv. Very smart devices!
    Thanks for your reply.
    The builder always uses the low end model to cut the cost, I am not sure if they are willing to do that.

  5. #5
    Join Date
    Apr 2008
    Posts
    8
    I wish the builder could do that.

    Quote Originally Posted by Mr Bill View Post
    Yea I have a good fix for that get them to remove those Carriers and install RUUD's and you
    won't have any problems period, and surly not a noise problem outside, matter fact you will
    have to listen hard to hear them...

  6. #6
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246

    bottom of the line units

    Those units are noisey and would compare to ruuds higher end models. But if you want something far better try Carriers APA5 or ANA1 s . Then you will have no problem with noise or efficiency and I don't think Ruud can even get on the same page.
    Do it right the first time.

  7. #7
    Join Date
    Dec 2006
    Location
    Fayetteville,Arkansas
    Posts
    1,427
    The STA and the ABA are the entry level systems offered from Carrier. I would have to check the match ratings but most likely the reason for the 5 ton evap coil is to get the rated 14 SEER from the condensor. Looking over that list of mathed systems I have seen a few that I thought were pretty far out there. Like using a 2.5 ton condensor with a 4 ton evap coil matched to 5 ton drive furnace to get 15 or 16 SEER. Your system should be just fine.
    If you choose not to decide you still have made a choice.

  8. #8
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,113
    Quote Originally Posted by mannyleonard View Post
    Those units are noisey and would compare to ruuds higher end models.
    Yea right looks like you know a whole bunch about RUUD's units, everyone I install the very first thing "every" customer says is man that thing is quiet and only a carrier blue oval cult person would say what you did.
    Bottom line is they all really suck in some way there is none perfected yet not even your Blessed Blue Ovals, I actually work on more of them than any other unit out there, and don't even get me started on there leaky evaporator coils, were changing out one this morning.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  9. #9
    Join Date
    Jul 2007
    Location
    Jacksonville, Fl
    Posts
    219
    You are fine,
    The A/C contractor who installed the system should supply you with the product data sheet upon request.
    Here is
    Product Data Sheet 24ABA
    You will find that the combination is ok,

    Scroll down to the combination ratings
    048---31
    CNPH*6024A**
    46,000 BTU
    TDR&TXV
    13.50 SEER
    11.20 EER
    58CV(A,X)090---16

  10. #10
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    THe BTU output is determined by the compressor not the evap coil, they shouldnt even put BTU ratings to them as it just causes confusion such as in this case.

    that appears to be an ARI listed match, so stop worrying

    ARI reference # 737065

    http://www.aridirectory.org

  11. #11
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    Quote Originally Posted by Mr Bill View Post
    Yea right looks like you know a whole bunch about RUUD's units, everyone I install the very first thing "every" customer says is man that thing is quiet and only a carrier blue oval cult person would say what you did.
    Bottom line is they all really suck in some way there is none perfected yet not even your Blessed Blue Ovals, I actually work on more of them than any other unit out there, and don't even get me started on there leaky evaporator coils, were changing out one this morning.
    come on, they have fancy thermostats, that makes them better.

    [IMG]http://www.*************.com/images/smilies/jerry.gif[/IMG]

  12. #12
    Join Date
    Dec 2006
    Location
    Fayetteville,Arkansas
    Posts
    1,427
    Quote Originally Posted by Mr Bill View Post
    Yea right looks like you know a whole bunch about RUUD's units, everyone I install the very first thing "every" customer says is man that thing is quiet and only a carrier blue oval cult person would say what you did.
    Bottom line is they all really suck in some way there is none perfected yet not even your Blessed Blue Ovals, I actually work on more of them than any other unit out there, and don't even get me started on there leaky evaporator coils, were changing out one this morning.
    Talk about the pot calling the kettle black. You're just as loyal to the brand you sell as anyone else. Seems you said to toss out the Carrier and install the Rudd/Rheem name and all of her problems would be solved.

    I do have to wonder why I can call the local Rheem distributer and be told that a high seer rated R410-a unit is not available other than special order even though there is a Rheem/Ruud plant 30 minutes away. The reason? The TM says there just isn't any interest from the dealers to offer and install the better line of equipment so they don't tie up warehouse space.

    I sell Carrier and like you or anyone else I'm proud of what we sell. Carrier and Trane are always leading the way in new products and designs and as you would expect there are problems from time to time. Rheem/Ruud plays it safe and waits to see how new technology fares and then 4 to 5 years later join in. That's why they're not the best nor are they the worst, just sort of middle of the road.
    If you choose not to decide you still have made a choice.

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,594
    Keep in mind. Their is no 4.5 ton.
    So the coil match up for a 4 ton condenser can't be 1/2 ton larger, it has to be the full ton when going to a larger indoor coil.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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