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  1. #27
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    Quote Originally Posted by BaldLoonie View Post
    3 tons for well insulated new construction in WI sounds big to me. Here, further south, a 20 year old house that size with less insulation would be 2.5 tons. Something fishy somewhere. 64 out the vents is really high for a 76 degree house.
    My take on the possible plethora of causes:

    Grossly over sized system trying to pump through drinking straws, per chance? There be holes in them there ducts?

    3 tons feels too big for a brand new energy star insulated house with very little glazing exposed. The HERS raters I communicate with on another site instantly suspect shoddy engineering when the spec calls for more than one ton per 1000 sf.

    Something is definitely wrong, that thing should recover in 15 minutes. And with long run cycles you report, AND A DEHUMIDIFIER RUNNING, the RH is way high.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  2. #28
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,431
    3.0 tons
    12,000 BTU per hr/Ton
    36,000 btu/hr
    66% Efficiency
    23,760 Effective BTU/Hr
    0.74 SHR
    17,582 SENSIBLE
    390 CFM/TON
    1,170 CFM TOTAL
    13.91 F

    So, I guess one has to say that the system was likely underperforming by at least 30%.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #29
    Join Date
    Jun 2008
    Location
    NW Florida
    Posts
    713
    Quote Originally Posted by rickboggs View Post
    If humidity is in the low 40's
    And the outside temperature is not above design conditions of 95*.

  4. #30
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by meoberry View Post
    And the outside temperature is not above design conditions of 95*.
    I just used Goodman expanded data. I used the 3 ton. And yes, at 95 outside, 75 inside, 59 wb, 1275CFM gives you a 20 degree temperature across the coil and 75db/59wb is about 40% rh.... I think.... you might want to check for yourself, I've been known to be wrong.

  5. #31
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by dan sw fl View Post
    3.0 tons
    12,000 BTU per hr/Ton
    36,000 btu/hr
    66% Efficiency
    23,760 Effective BTU/Hr
    0.74 SHR
    17,582 SENSIBLE
    390 CFM/TON
    1,170 CFM TOTAL
    13.91 F

    So, I guess one has to say that the system was likely underperforming by at least 30%.
    What are these numbers

  6. #32
    Join Date
    Dec 2005
    Posts
    1,923
    Quote Originally Posted by meoberry View Post
    And the outside temperature is not above design conditions of 95*.
    This is the best that I have seen.

    I wanna buy that for $1.00 and I hope the owner does too.

  7. #33
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,431

    Hmm ? ? What's reasonable ...

    Quote Originally Posted by rickboggs View Post
    What are these numbers
    Trying to 'rationalize' how one can come up with a dT of only 14'F.

    I expect S.H.R. should be ~ 0.74,
    if the Relative Humidity is reasonable ( 48% _ +/- 5%).

    So, the performance must be 'off' some with a Rather Low dT.

    http://www.engineeringtoolbox.com/la...oad-d_245.html
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  8. #34
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by dan sw fl View Post
    Trying to 'rationalize' how one can come up with a dT of only 14'F.

    I expect S.H.R. should be ~ 0.74,
    if the Relative Humidity is reasonable ( 48% _ +/- 5%).

    So, the performance must be 'off' some with a Rather Low dT.

    http://www.engineeringtoolbox.com/la...oad-d_245.html
    Dan, have you looked at the expanded data in the Goodman link I posted?

  9. #35
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by just_opinion View Post
    This is the best that I have seen.

    I wanna buy that for $1.00 and I hope the owner does too.
    Dude, you're losing money!

  10. #36
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,431

    Hmm Poor Performance ... ...

    Quote Originally Posted by rickboggs View Post
    Dan, have you looked at the expanded data in the Goodman link I posted?
    Page 12
    75 DB / 63 WB / 51.6% R.H.
    http://www.thermalinc.com/math/wetbulbcalc.htm

    S.H.R. 0.76 to 0.79
    18' -19 'F dT at 95'F outside / 51% inside

    Any dT < 18'F seems to be poor system performance @ range of 50% R.H.,
    if the air flows are comparable. ( 1,125 - 1,275 CFM)
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  11. #37
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by dan sw fl View Post
    Page 12
    75 DB / 63 WB / 51.6% R.H.
    http://www.thermalinc.com/math/wetbulbcalc.htm

    S.H.R. 0.76 to 0.79
    18' -19 'F dT at 95'F outside / 51% inside

    Any dT < 18'F seems to be poor system performance @ range of 50% R.H.,
    if the air flows are comparable. ( 1,125 - 1,275 CFM)
    I think this has gone past my point, which was at certain conditions I can have a different delta t's, the expanded data shows a range from 10 to 20, with performances from 31500 btus to 37700 btus and shr's from .88 to .38. I'm done.

  12. #38
    Join Date
    Mar 2007
    Location
    wedged in freezer shelf
    Posts
    7,210
    Quote Originally Posted by MM#7 View Post
    what exactly is a plethora of factors mean?
    http://www.youtube.com/watch?v=-mTUmczVdik

    Is there a central return and where it the t-stat mounted?
    “If You Can Dodge A Wrench You Can Dodge A Ball”

  13. #39

    Additional Ino

    Sorry but you're losing me with some of the technical speak here.

    To answer a couple of more questions that have been posted. The day that we measured this (as well as most days) we've kept the AC on all day. Our cycle is 80 during the day when we're gone, we drop it to 78 at 4pm about 1.5 hours before we get home, then down to 76 at 9pm when we go to bed.

    There is a cold air return on the wall that the thermostat is mounted on. It is right next to it. Is this good or bad.

    We've got the HVAC guy coming back shortly and am also planning to call Carrier and a second technician in if he continues to say nothing is wrong.

    I measured the temp coming out of the vents by placing a thermometer over the vent and leaving it there for around 10 minutes while the air had been running the whole time.

    Seems to be an agreement that something is not running right about this system from what I'm gathering?

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