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  1. #1

    New Home - Concerned about install

    I have a new home that is nearly completed. The AC Company is ready for their final draw, but I am concerned that the system is not working properly.

    Home Size: 6200 sqft
    System - Trane XL19i Heat pump 5-ton (lower-1), 4-ton(upper-1), and 3-ton(lower-2) / c variable speed air handler.

    To test the system I set all 3 to 68 degrees. The house was 85 downstairs, and 84 upstairs prior to the test beginning @ 9:30am. Outside Temp was 85.

    10:35am - Outside 86, Temp 78 in house
    12:22p - Outside 92, Temp 75 in house
    2:15p - Outside 92, Temp 72 in house
    4:11p - Outside 95, Temp 72 in house
    6:30p - Outside 95, Temp 70 in house

    To compare, I went to my current home @ 2:30p, went to my master bedroom, temp was 83. I changed the thermo to 68, and at 3:45, it was 68. This is a trane XL14i 2 ton unit (NOT HEATPUMP)

    I believe I have a problem, but I don't know what basis to complain about other than this just isn't right. I mentioned to the tech on Friday that it wasn't coolling proper, and he checked pressure (very quickly) and said it is normal, and new systems need to break in. I feel that is BS, so I am hoping someone with a little knowledge might tell me a smart question I can ask.

    Thank You,
    Ronnie

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,174
    Do you have a lot of windows, or large windows.
    A lot of glass sliding doors.
    Any large exhaust fans that were running.
    Did they actually do a load calc, 12 tons for 6200 sq ft new construction, seems way oversized. Sounds like a rule of thumb sizing.(500 sq ft per ton), Your coming out to 516 sq ft per ton.

    What mod thermostats do you have.

    If the humidity was high. It could take a long time for them to cool down the house for the first time, while reducing the humidity most newly constructed houses have.
    But with what sounds like a large over sizing, it shouldn't take too long.



    Questions to ask.

    How was system size determined. Rule of thumb, or actual calculations based on construction.
    Were the ducts tested for leakage. If so what is the leakage rate.
    Are the units wired right.
    What are the SC, and SH of the units in first and second stage.
    What are the blower speeds set to.
    Do you have fresh air intakes on any of your systems. If so, what CFM are they set for.
    How are they controlled.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Aug 2008
    Posts
    35
    "New systems need break in" ?

    LOL!.....the wonderful world of heat pumps perhaps but was the shell of the house cool to start with?....no right?
    I would keep in mind that you cant kick many systems down mid day and ask for perfection.
    Start and keep the system running from A.M. through P.M. and see what happens.
    You cant expect this system to be able to cool against a hot envelope while the sun continues to add to it.

    If a 24 hour period doesn't do it then you have a real issue.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,245
    Sounds pretty good to me! Dropping 6200 sq ft from 84/85 to 70 in the same day is impressive. Remember you aren't just cooling the air, you are cooling everything in the house. Heat in walls, floors/carpet, furnishings... and as been mentioned, you may have a lot of humidity in the air from being open. I'd hazard the guess you are oversized for normal conditions. Lucky it is 2 stage equipment.

  5. #5
    Join Date
    Feb 2006
    Location
    Tn.
    Posts
    1,344
    Quote Originally Posted by BaldLoonie View Post
    Sounds pretty good to me! Dropping 6200 sq ft from 84/85 to 70 in the same day is impressive. Remember you aren't just cooling the air, you are cooling everything in the house. Heat in walls, floors/carpet, furnishings... and as been mentioned, you may have a lot of humidity in the air from being open. I'd hazard the guess you are oversized for normal conditions. Lucky it is 2 stage equipment.

    a/c is not designed to reach 68 on a 95 degree day. Sounds good to me too.

  6. #6
    Quote Originally Posted by beenthere View Post
    Do you have a lot of windows, or large windows.
    A lot of glass sliding doors.
    Any large exhaust fans that were running.
    Did they actually do a load calc, 12 tons for 6200 sq ft new construction, seems way oversized. Sounds like a rule of thumb sizing.(500 sq ft per ton), Your coming out to 516 sq ft per ton.

    What mod thermostats do you have.
    I have the honeywell / trane top of the line /c humidity control, etc.
    If the humidity was high. It could take a long time for them to cool down the house for the first time, while reducing the humidity most newly constructed houses have.
    But with what sounds like a large over sizing, it shouldn't take too long.
    The system has been running keeping the house at 50% humidity or 83. When I started the test the house was at 51% humidity, so it was comfortable, just not cold.

    I did have 3 bids, and 2 of those included load studies, that were very close to the same. The house is using a very good quality window, with the larger windows on the north / south, and large porches over them. THe east/west side has very few, very small windows. 2x6 construction with 4" foam, and cellulose insulation. The attic has foam, loose insulation and metallic backed boards to reflect. Prior to the ac being installed, the house was so tight that it was very comfortable with just a few fans.

    We also have the trane "FreshEffects" ERV, but i have it set to 10% right now.

    Questions to ask.

    How was system size determined. Rule of thumb, or actual calculations based on construction.
    Were the ducts tested for leakage. If so what is the leakage rate.
    Are the units wired right.
    What are the SC, and SH of the units in first and second stage.
    What are the blower speeds set to.
    Do you have fresh air intakes on any of your systems. If so, what CFM are they set for.
    How are they controlled.
    Thank you. Can you tell me what SC and SH stand for?

  7. #7
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,569
    I would say it is a bit oversized to be able to draw the temps down to 70 from 85 as the day was getting hotter. I would also say a manual J could have been done, but ignored. You can complain about the manual J, but then they are probably going to tear out the equipment you have and put in smaller equipment and it most likely will not get the house colder than mid 70's during the heat of the day.

  8. #8
    Quote Originally Posted by bt1 View Post
    "New systems need break in" ?

    LOL!.....the wonderful world of heat pumps perhaps but was the shell of the house cool to start with?....no right?
    Yes, it was running prior to my start. It was keeping the humidity at 50%. I did start the test around 9:30a.

    I would keep in mind that you cant kick many systems down mid day and ask for perfection.
    Start and keep the system running from A.M. through P.M. and see what happens.
    You cant expect this system to be able to cool against a hot envelope while the sun continues to add to it.

    If a 24 hour period doesn't do it then you have a real issue.
    My current home is within 3 miles of the new home, and the construction is absurdly different. New home is foamed walls, and laid out with consideration to sun patterns etc. Old home has 2x6 with cellulose but no foam, and major windows facing east/west. Old home has alum windows.

    All that to say that when I went home mid-day and cooled the house I got performance that I would expect.

    I believe the problem to be that the second stage cooling is not working. Based on fan speed, and air temp (no thermo, just my face and hands and gut feeling), it is not fast enough nor cold enough.

  9. #9
    Quote Originally Posted by bmathews View Post
    I would say it is a bit oversized to be able to draw the temps down to 70 from 85 as the day was getting hotter. I would also say a manual J could have been done, but ignored. You can complain about the manual J, but then they are probably going to tear out the equipment you have and put in smaller equipment and it most likely will not get the house colder than mid 70's during the heat of the day.
    What is a manual J?

  10. #10
    Quote Originally Posted by redbaron73 View Post
    What is a manual J?
    Found it here http://www.hvacloadcalculations.com/

    The AC company provided me with a computerized printout "Wrightsoft version 6" Building analysis, Entire House.

    Lots of pages in a pdf doc, I could post if anyone here would understand it.

  11. #11
    I should also mention that all ducts are R8 unless they are between floors, then they are R6.

  12. #12
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by BaldLoonie View Post
    Sounds pretty good to me! Dropping 6200 sq ft from 84/85 to 70 in the same day is impressive. Remember you aren't just cooling the air, you are cooling everything in the house. Heat in walls, floors/carpet, furnishings... and as been mentioned, you may have a lot of humidity in the air from being open. I'd hazard the guess you are oversized for normal conditions. Lucky it is 2 stage equipment.


    i agree,

    except for the oversized comment!

    are you saying you don't think 95 degrees is a normal condition!

    my comment to the home owner would be to get the installing company to send a service tech out

    expect to pay for his time

    make sure you are there to watch so you understand the operation of the system

    get the service tech to check one system at a time for these things

    1. all dip switches set properly
    2. all t-stats are set-up properly
    3. all refrigerant charges are correct
    4. all systems run in high speed and low speed properly
    5. all filters are installed properly
    6. all ductwork is intact

    if all systems are operating properly atleast you will be happy!

    if adjustments are needed, the installing company should deduct the time it takes to adjust those things!



    .

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,174
    Quote Originally Posted by redbaron73 View Post
    Thank you. Can you tell me what SC and SH stand for?
    Sc, Subcooling.
    SH Superheat.

    You can post your load calcs.
    Contractor locator map

    How-to-apply-for-Professional

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

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