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  1. #14
    Join Date
    Jul 2011
    Posts
    354

    Hmm

    Quote Originally Posted by Mr Bill View Post
    4-tons? maybe they thought she was one hot Momma.
    she was 68yo going on 75, but is still kicking!

  2. #15
    Join Date
    Mar 2010
    Posts
    195

    Everbody is working it backward, Starting with the answer.

    Quote Originally Posted by tedkidd View Post
    Many ask if there is a tonnage to sf rule of thumb, afraid that if equipment gets too small they will sail off the edge of the earth. Kinda like happened to explorers up until Columbus magically reshaped the earth from a pancake to a globe.

    That reshaping is occurring now in our industry. (of course stupid setback strategy thing needs to be weeded out of the public consciousness to really succeed).

    Well, there are some using this rule of thumb in reverse. If your equipment is more than 1 ton per 1000 square feet, the HERS guys suspect crappy work and pull out the magnifiers.

    Here's a GREAT article on the subject...
    Hey Kid,

    Manuel J Says,

    "If they want to do ENERGY STAR new homes, though, and their Manual J reports are coming to me, they should know that I've got my own rule of thumb - 1000 square feet per ton. When that 2000 square foot house comes to me with a 3 ton air conditioner, I have no choice but to look further because they didn't pass my rule-of-thumb test."

    Hey but what about a 3 ton 2 stage. 21,000 BTU/hr on fist stage does he throw this out for being to big or to small?

    So if you want to get past this guy He's telling you where you gotta be.
    The fact that if you're not moving enough air, and the builder added 3 skylights, and he's not the one the doesn't get their final check, gets sued, etc...In Boston, with tight houses he may also be correct. Either way, it doesn't matter.
    You gotta work it backwards. Give em the number they want. Fist thing you learn with your new super duper load calc program.

    Some utility guys look at your sensible: latent ratio. Other inspectors have their own pet ratio's, kinda like a game . Weather we are doing RNC or Replacements we learn how to get the numbers we need. No one uses the tool and just says OK, that's it (in AOR you would be 1 ton under the rest of the guys and look silly if you followed the bible). It's all about getting the number we want, need, or have to have. Science? Give me a break. At least with new houses we have prints, specs, codes, etc..with old houses we have no clue on any of this, just 6-7 guesses. What number do you want? No problem.

    So what to do? Take control of the distribution(focus on this), tighten/seal as best you can and sell modulating stuff to smart customers that Give.A.S.ht.

    But lets not pretend we use our program to give us an answer, we started with that.

    ACBD

  3. #16
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,290
    My house is 1587 sq ft. Currently has a 3 ton which is way too big. 1.5ton for 1587 sq ft seems quite small. i don't mind the AC not keeping up when outside temps exceed design conditions but don't want it to be 85 in here either.

  4. #17
    Join Date
    Dec 2008
    Location
    Littleton, Co
    Posts
    54
    The guy that is supposed to be installing my system didn't like the 3.5 tons that HVAC Calc came up with. He and the counter guy at the supply house think that I really need 6 tons. He will install the 4 ton unit, but he won't guarantee that I'll like it. He won't guarantee the 5 ton unit he bid either. The only way I'll get a guarantee is if I get the 6 ton?

    Adam

  5. #18
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,002
    I feel all the current sq. ft. per tons rules will be out the window, when the new Al Gore global warming LC Guide comes out, I am guessing we will be looking at around 150 sq. ft. per ton.
    __________________________________________________ _______________________
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  6. #19
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989

    Hmm

    Quote Originally Posted by MLeonhardt View Post
    Judging by the area I am in this summer, 27 days straight of over 100 degree temps. I have 4 neighbors that did the energy audit and did the recommended. Guess what ! Not one of them can hold less than 85 in the house with the units running 24/7. Expensive lesson in electricity usage and equip cost.

    So much for design temps..
    Well, then they have some unresolved problems, because I have well over 1200-sq.ft to the TON & a week or so ago WI Public Radio announced a 127-F Heat Index very close to my home.

    My (two) Half-Ton Window units kept the temp around 77-F & the humidity around near 64%, it felt like a refrigerated home compared to outdoors; I was very comfortable.

    When I go to bed 10:30 or 11-PM I turn the Room A/C's off, & I'm comfortable until morning! 80-F is about as high as it gets overnight & I'm very comfortable!

    If they do everything right those systems will do far better than an 85-F, & will keep them comfortable; something is not right besides the BTUH sizing..

  7. #20
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989

    Lightbulb

    Quote Originally Posted by adamt View Post
    The guy that is supposed to be installing my system didn't like the 3.5 tons that HVAC Calc came up with. He and the counter guy at the supply house think that I really need 6 tons. He will install the 4 ton unit, but he won't guarantee that I'll like it. He won't guarantee the 5 ton unit he bid either. The only way I'll get a guarantee is if I get the 6 ton? Adam
    Okay, let us hear what U have that U even need 4 or 5-Ton; let alone 6-Tons.

    When 4-Ton & larger is installed it seldom has adequate ducting, usually low airflow per ton, & not nearly enough RA filter area, etc.

  8. #21
    Join Date
    Mar 2010
    Posts
    195

    Several Suggestions

    Quote Originally Posted by udarrell View Post

    Well, then they have some unresolved problems, because I have well over 1200-sq.ft to the TON & a week or so ago WI Public Radio announced a 127-F Heat Index very close to my home.

    My (two) Half-Ton Window units kept the temp around 77-F & the humidity around near 64%, it felt like a refrigerated home compared to outdoors; I was very comfortable.

    When I go to bed 10:30 or 11-PM I turn the Room A/C's off, & I'm comfortable until morning! 80-F is about as high as it gets overnight & I'm very comfortable!

    If they do everything right those systems will do far better than an 85-F, & will keep them comfortable; something is not right besides the BTUH sizing..
    Hey Udarrel,

    Several suggestions,

    1st, don't listen to public radio, it will fill your head with communist thoughts like unfunded federal mandates so support HVAC sales.

    2nd, stay up latter and watch Leno, it will be cooler when you go to bed.

    ACBD

  9. #22
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,411
    Quote Originally Posted by udarrell View Post


    Okay, let us hear what U have that U even need 4 or 5-Ton; let alone 6-Tons.

    When 4-Ton & larger is installed it seldom has adequate ducting, usually low airflow per ton, & not nearly enough RA filter area, etc.
    Here ya go Darrell.
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  10. #23
    Join Date
    Feb 2010
    Location
    Cal
    Posts
    1,596
    Quote Originally Posted by udarrell View Post

    Well, then they have some unresolved problems, because I have well over 1200-sq.ft to the TON & a week or so ago WI Public Radio announced a 127-F Heat Index very close to my home.

    My (two) Half-Ton Window units kept the temp around 77-F & the humidity around near 64%, it felt like a refrigerated home compared to outdoors; I was very comfortable.

    When I go to bed 10:30 or 11-PM I turn the Room A/C's off, & I'm comfortable until morning! 80-F is about as high as it gets overnight & I'm very comfortable!

    If they do everything right those systems will do far better than an 85-F, & will keep them comfortable; something is not right besides the BTUH sizing..
    What would your opinion be of your tonnage performance if attached to a typical/old duct system?

  11. #24
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,781
    Guidelines rarely, if ever work out optimally... but they will most likely get you close if set correctly for a given region/building construction.

    1ton/1000sq. ft. is laughable in my region, where homes are built cheap, and the weather is quite hot. I've got 1.66 ton/1000sq ft, and it doesn't quite maintain on the hot days. (seriously tempted to get a single 1 ton window unit to help out on the hottest days).

  12. #25
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,781
    Quote Originally Posted by udarrell View Post

    Well, then they have some unresolved problems, because I have well over 1200-sq.ft to the TON & a week or so ago WI Public Radio announced a 127-F Heat Index very close to my home.
    To be fair, if you have a reasonably tight home, heat index is not proportional to cooling demand, only sensible (dry bulb) is. If the humidity isn't getting in, that 127°F heat index is NOT contributing to your cooling demands, but only the, say 90°F dry bulb is pushing heat into your home. Heat index has no bearing on condenser efficiency either (in fact, to a minimal degree, more humid air at the same temperature will work better on the condenser, as it will attain less temperature rise crossing the coil, due to a higher heat capacity).

  13. #26
    Join Date
    Jul 2011
    Posts
    354

    Confused

    Quote Originally Posted by 54regcab View Post
    My house is 1587 sq ft. Currently has a 3 ton which is way too big. 1.5ton for 1587 sq ft seems quite small. i don't mind the AC not keeping up when outside temps exceed design conditions but don't want it to be 85 in here either.
    you say 3 tons for 1587sq.ft. is way too big? you say a 1.5 ton seems quite small, what do you think is the right size for your house as it sits this minute w/o improvements.one observation i'll tell you right now, and at least this is in the nyc tri state area. if you go into a guys house who's owned his house,20 years , and say he has a 3 1/2 ton unit and he's happy, you do a load calc, you decide to give him a 2 1/2 ton unit! w/o any other modifications! and then he runs into a 97 degree day! do you think you'll get a call? do you think he'll be ######@? do you think he'll want to hear, it's running all day and look at all the humidity, he's taking out? good luck. these are tough areas your getting into when you start down sizing peoples units after the've lived with the other unit for years. tread gently out there!JMHO.

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