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  1. #1
    Join Date
    Apr 2006
    Posts
    81

    Thought my home was tight?

    Very hot....it was 109 here today. I have a Carrier 16 seer 4 ton infinity heat pump. My home is a 2000 sq ft home with high celings. Set thermostat at 77, and it held there until 3:00p.m.. Then it went to 80 and has not come down yet. I have my unit serviced twice a year and just had it done. Measured the temp out of the return and intake. There is a 18 degree difference at the moment. Since its close to 20, I assumed that its doing its job. So, to my question. If my temp difference is 20, why cant my unit keep up?

  2. #2
    Join Date
    Jan 2008
    Posts
    1,992
    Outdoor temp is above design temp?
    If it is, then your system is probably sized right, and performing properly.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  3. #3
    Join Date
    Apr 2006
    Posts
    81
    Quote Originally Posted by 2old2rock View Post
    Outdoor temp is above design temp?
    If it is, then your system is probably sized right, and performing properly.
    I have been told that our design temp for our area is 100.

  4. #4
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    Quote Originally Posted by kkmcewen View Post
    I have been told that our design temp for our area is 100.
    If your design temp is 100 and its 109 and you are 3 degrees above your set point, you are doing good.
    Karst means cave. So, I search for caves.

  5. #5
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    I know my home is tight.
    4,000 sq. ft. 2 ton heat pump, 108 outside, 73.8 inside.

  6. #6
    Join Date
    Dec 2007
    Location
    houston, texas
    Posts
    3,787
    Quote Originally Posted by paul42 View Post
    I know my home is tight.
    4,000 sq. ft. 2 ton heat pump, 108 outside, 73.8 inside.
    It's either the tightest home in Texas or your pulling my leg, 2 tons isn't gonna do much on 4000 sq ft, much less in Dallas
    I'm not tolerating Political Correctness anymore, from now on it's tell it like it is.

    Veto Pro Pak - The best tool bag you'll ever own






  7. #7
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    Quote Originally Posted by Texas-Tech View Post
    It's either the tightest home in Texas or your pulling my leg, 2 tons isn't gonna do much on 4000 sq ft, much less in Dallas
    Put the air handler & duct work in conditioned space.
    Shade all the windows in the summer.
    Make the house air tight.

    West end of Fort Worth.
    Upstairs, it is 73.9, downstairs is 68.

  8. #8
    Join Date
    Jun 2009
    Location
    Northwest IN/Chicago
    Posts
    268
    Quote Originally Posted by paul42 View Post
    Put the air handler & duct work in conditioned space.
    Shade all the windows in the summer.
    Make the house air tight.

    West end of Fort Worth.
    Upstairs, it is 73.9, downstairs is 68.
    Are you sure that's not two two ton units? Either way I would love to know your secret. Even if it is perfectly shaded and insulated, sealed etc that still sounds crazy.

  9. #9
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    Quote Originally Posted by Gus-Herb94 View Post
    Are you sure that's not two two ton units? Either way I would love to know your secret. Even if it is perfectly shaded and insulated, sealed etc that still sounds crazy.
    It is an unusual house.
    The house is on a slope. The top floor is the living quarters and is 2,300 sq. ft.. The bottom floor is storage and mechanical with no windows and only one exterior door.

    The bottom floor is all above ground with the exception of the east end which faces the fill under the garage. The bottom floor is the same size as the top floor, but due to the slope of the ground, the ceiling is only 6' at the east end, so I call it 1,700 sq. ft. So, I have at least 4,000 sq. ft. of conditioned space, all above ground.

    All of the duct work is in the bottom floor and feeds wall stacks with vents about a foot below the 10 foot ceilings in the top floor.

    The house has 3 foot eves and large porches which shade all of the windows on the north & south. The east is shaded by the garage. The west has 3 small windows tucked up under the eves. They have very low e glass and don't get any sun until after 6. The rest of the windows in the house don't see any sun at all during the summer.

    The attic has R49 insulation. The walls have 2" of polyiso foam board between the sheathing and the brick, all sealed with aluminum foil tape. I spent a lot of effort air sealing the house while in construction. I sealed the outlets, sealed the top plates, added gaskets behind the drywall, and spent a few hours in the attic with a foam gun before the insulation was blown in. On the walls, between the polyiso foam and the sheathing is a peel & stick roofing membrane that is completely air & water tight.

    I heat & cool at least 4,000 sq. ft. with one 2 ton heat pump in north central Texas.

  10. #10
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,541
    Quote Originally Posted by Texas-Tech View Post
    It's either the tightest home in Texas or your pulling my leg, 2 tons isn't gonna do much on 4000 sq ft, much less in Dallas
    Maybe 2500 of that is an unconditioned garage? I find it hard to believe as well. 2000 sq. ft. per ton? Holding 74 at 109? I've worked on some pretty efficiently built houses and 1000 sq. ft. per ton in Texas is really pushing it.
    I like DIY'ers. They pay better to fix.

  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by Texas-Tech View Post
    It's either the tightest home in Texas or your pulling my leg, 2 tons isn't gonna do much on 4000 sq ft, much less in Dallas

    Oh, it's possible, but the he pluncked down at least an extra $25k in insulation when he built his home... and probably doesn't have a lot of whole lot of windows... or those windows were mighty expensive as well. SO let's see, increased construction costs of $30k, so with a 30 year loan and interest that's what, $150/month extra?

    I have a 3200swft home that requires around 4-1/2 tons of cooling, if I cut my cooling and heating bills by 70%, I'd still only be saving around $140/month. And I'd probably have to give up 1/2 of my 42 windows to do it.


    Sorry, I just like to deflate the ego a little of those that gloat how low their electrical use is. There's no free lunch. You cna live in a berm home and have very low bills and low constructon costs, but then you have to live in a berm home... a cave.

    Nope...no free lunch. Goethermal for example is great, but you have to drop 5 figures to drill the wells.

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,317
    Quote Originally Posted by motoguy128 View Post

    Sorry, I just like to deflate the ego a little of those that gloat how low their electrical use is.
    I don't think Paul is gloating much, just stating facts arising from the extra care he took planning and building his home.

    He also hasn't said much about energy consumption. He's said a great deal about how well his supposedly undersized system keeps his house comfortable.

    We tend to get overly hung up on energy costs, IMO. Comfort drives energy costs. If people aren't comfortable, they'll run their HVAC into the ground to get comfortable, and faint when the high bills come since they can never meet their goal.

    Paul has an advantage over many of us. Should the electrical grid drop power to his house in the dead of winter or on a 110 degree day like we had yesterday, he's not immediately in a world of hurt. Unless he has a backup generator, he could probably coast through the cold or heat until power can be restored without a great deal of discomfort.

    What Paul has, over and above low energy cost, is a house that is truly a shelter in more ways than one. Not only will it keep him dry, it keeps him warm and cool easily. I also suspect he does not live in a cave. When you begin to understand what makes buildings that are difficult and costly to heat and cool be that way, you begin to realize it's not always what folks want to blame for being the culprit. And sometimes it's a combination of the obvious and less obvious. That is why energy audits can have value, but if I had my way they'd be called "comfort audits", because low bills are just one source of comfort. Peace of mind that your house won't freeze you to death or kill you via heat stroke is another form of comfort.


    There's no free lunch. You cna live in a berm home and have very low bills and low constructon costs, but then you have to live in a berm home... a cave.
    As one who participated in earth-sheltered housing concepts in my younger days, there are good and bad examples of this concept, as is true with anything. If you want an example of an early prototype berm home that was light and airy, check this one out:



    This house was designed by Frank Lloyd Wright and built in the 1940's. Some would say it's a bit heavy on glass, and on cloudy winter days that might be an issue, but think about when this house was made, and what could be done with current technology.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  13. #13
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,963
    I have the next thing to a free lunch.

    Two very low cost half-ton room A/Cs in a1937 farm home that I didn't have to do anything with to get extremely low electric bills.

    If I had central installed that new furnace indoor blower (.5-hp; high spd; 7-amps @115-volts 805-watts.) would use as much or more wattage than either the 1st floor or 2nd floor A/C uses. The window A/C on the 2nd floor doesn't get used much;usually only a short while before I hit the sack.

    The floor fan for the room A/C doesn't use but little juice on low or medium.

    Well, that's if you're running 3-Ton of cooling; I'd probably be running 1.5 or two Ton so I could us a 3-Ton indoor coil for lower pressure-drop resistance operating in the heating mode.
    Last edited by udarrell; 08-04-2011 at 11:32 AM. Reason: Clarity...

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