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  1. #14
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by BaldLoonie
    In our suburb, we have a common floorplan 3 bedroom 1800 sq ft ranch. We've installed 2, 2.5 and 3 tons of cooling on this exact same house. So which is right? Can you guys in Louisiana or California tell me? You told him his was wrong without seeing the house or knowing much about it.

    The answer is all of them are right. Anybody going by sq ft doesn't know what they are doing. The 2 ton homes are well shaded. The 2.5 ton homes aren't shaded but face north-south with no east-west windows. The 3 ton homes are east-west facing with no shade. Hmmm, all the same house, same sq ft with radically different cooling needs. Guess that's why the Manual J was invented.

    Do your California and Louisiana homes have the same insulation as his? Gee, you can't answer that - you don't know what he has yet you know his A/C is undersized. Well, my guess is he has R38 ceiling and R19 walls. That what they do in your area?

    Ricardo, if you are staying comfy in the extreme heat we've been having in the upper Midwest, your system is NOT undersized. hilton's 5 ton would have you running dehumdifiers all over the place in the normal humid 82 we typically have because it would be short cycling something fierce.

    All very true!

  2. #15
    Join Date
    Jun 2002
    Posts
    38
    Insulation is R15 in the walls. Most of the ceilings are R-38 except in the cathedral ceiling areas where they used R-30 batts. The house is fairly air tight. The contractor did a pretty good job sealing it up. Anything that he missed I've taken care of over the past two years. It definitely felt very refreshing coming in the house after doing three hours of yard work in the ninety-five degree heat.

  3. #16
    Join Date
    May 2005
    Posts
    428
    Baldloonie is correct. hey bald staying busy in indy i bet im just down the road in terre haute

  4. #17
    Join Date
    Jun 2004
    Posts
    956
    thanks for pointing that out Baldloonie,

    I can bet hilton and moe have heating systems waaaayyyyy undersized

  5. #18
    Join Date
    Apr 2005
    Location
    Inland Empire,CA
    Posts
    56
    bald loonie. not an installer or engineer.i'm in service. thousands of homes like this in cali. are you saying these home installers don't use manual j or using cheap insulation material.no difference if house on north or west shaded or not.i have also worked in resi additions never used manual j. boss used sqft and some duct calculations. this is also in a class given by ihaci in san diego. bottom line houses, customers have been fine.

  6. #19
    Join Date
    Jun 2004
    Posts
    956
    I think loonie is trying to point out there are many variables to consider when sizing

    you are in cali, much different enviroment than chicago, you cant say the system is undersized, it may be for your area but not this way.

    with the example he shows that a rule of thumb could have led to some very unhappy people or worse situations.

    I have found that out this way, no one, does a man j.

    sister needs one for an addition and cant find a company that can do one.

    I dont install so have'nt had the need.

  7. #20
    Join Date
    May 2005
    Posts
    428
    let me see if i understand this. we size the equipment by the sq ft and thats it ? that sounds easy enough. And all this time i have been wasting my time accounting for r-values ,window sq footage, etc,etc,etc. I remember some years back i installed central air system i home that was poorly insulated then a few monthes later the customer calls and said that mold was growing on baseboard.when i went to customers home she told me that she had the house re insulated, well now the system is to big this is why i dont go sq footage alone.

  8. #21
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    hiltontech & moe-air: damm glad you did not do my house?
    I suppose you think that 5000btu/hr does not keep my downstairs at 77F, upstairs at 75F = 2133sf, tri-level, Huntsville AL -- today --
    my util bill went up $20 last month due to a/c! from $64 to $84 = whole bill = water, sewage, elec, garbage ($14)

    had to stop & get T-shirt -- since I have cooled down from am walk

  9. #22
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    BaldLoonie and Dash are both right on the money. Every home has a unique heat load. Whether the house is shaded or not makes a huge difference in sizing requirements. It's called solar gain. Sounds like your system is sized properly, and running great. Have the coils cleaned yearly and have a preventative checkup done. Just don't let some bonehead try to add gas to it unless they can find and fix that leak. Refrigerants don't just leave a system slowly, unless there is a leak.

  10. #23
    Join Date
    Jul 2000
    Location
    NW IL.
    Posts
    3,935
    Loonie, The Bald One, is right manual J needs to be done for your house and heat gain, shading, window locations etc.





    Believe this link was posted somewhere here or another site, but needs reading again.

    Bigger Is Not Better:
    Sizing Air Conditioners Properly
    http://www.proctoreng.com/articles/bigger.html

    Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.

  11. #24
    Join Date
    Jul 2000
    Location
    NW IL.
    Posts
    3,935
    Design temp for Chicago area is 91 degree outside with a 75 inside according to HVAC Calc. With the temps and humidity we have been running right now in the midwest a perfectly designed system may run continuous during the day time and run a couple degrees higher temp. If you are staying comfortable don't panic the weather will soon change, hope soon, back to normal temps.
    Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.

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