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  1. #14
    Join Date
    Aug 2004
    Location
    Tyler TX
    Posts
    676
    Originally posted by coco
    wow i never thought about such large a/c 's down south we it takes a 4-5000 sq ft house to get 4 or 5 tons of cooling in mn
    Your homes up north are designed for severe temp differences in the winter being the reason yo can cool maybe up to a 3000 sqf home with a 2.5 to 3 ton ac. Just for kicks someday recalculate with wall insulation of r11 and cieling insulation of r19 and see the difference.

    I use the 600sqf per ton for estimating only. All of my homes are manual j calculated before quotes are given. In the Tyler Tx area I have homes of about 1800sqf with 2 to 4 ton systems. most get a 2.5 to 3 ton on new construction and 3.5 and 4 ton on older less well insulated homes
    HVAC Contractor, Tyler Texas.

  2. #15
    Join Date
    Jun 2005
    Posts
    64
    55 years of company experience my boss knows in 10 seconds what size furnace and a/c w/o manual j

  3. #16
    Join Date
    Feb 2002
    Location
    Houston Tx
    Posts
    344
    This question was most likley asked a week ago when our heat index was up around 105*, My own a/c at home would do the same thing, As far as 1800 sq ft per 3 tons is 600 per ton, in new construction here that would be called okay. not exact but close..

  4. #17
    Join Date
    Aug 2004
    Location
    Tyler TX
    Posts
    676
    Originally posted by coco
    55 years of company experience my boss knows in 10 seconds what size furnace and a/c w/o manual j
    After 55 years I bet he would know what will get it done.
    HVAC Contractor, Tyler Texas.

  5. #18
    Join Date
    Mar 2005
    Location
    Louisiana
    Posts
    211
    "As far as 1800 sq ft per 3 tons is 600 per ton"

    I misread, I thought it was 2400sq. ft.

    3 ton is about right.

  6. #19
    Join Date
    Aug 2004
    Location
    Texas
    Posts
    88
    this is only a suggestion, but I have been scratching my head over the same thing for some customers. I finally broke the code. Problem exist especially in the afternoon evening hours hottest part of day. What I found was that the return air grills are mounted in the wall in the hallway. The units are in a closet in the hall. you know mounted up off the floor, plenum going through the ceiling. Underneath is the return air area. Also opened up to the bare 2x4s, you could see the back of the bathtubs from the bathrooms. I am thinking you only want return air from the living area, but in this situation you are pulling return air right down from the attic by way of 2x4 channel. This is by default. So I closed the inside up. Pulling more return from the house and improved the air pressure coming from vents. Boy are those folks happy. They said they actually got cold sleeping last night.

  7. #20
    Join Date
    Mar 2005
    Location
    Louisiana
    Posts
    211

    thanks for the post thewoodman

    I might try the same here at my home because I as many others have a problem cooling my home between 3:00 and 6:00 pm, after that is cools like crazy, I insulated everything I could, I put this unit in when my home was built, even when it was brand new I had the problem, I understand why but explaining to the customers is not that easy to make them understand.

  8. #21
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323

    Question How BIG is Large

    Originally posted by coco
    wow i never thought about such large a/c 's down south we it takes a 4- 5,000 sq ft house to get 4 or 5 tons of cooling in mn
    FLoridian Architects just LOVE GLASS.

    5,000 S.F. house sometimes has > 1,300 S.F of Glass.
    That's > 5 tons right there.

    Whole house may need total of 10 to 12 tons depending on ceiling height ( upto 14') and house orientation.
    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

  9. #22
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,326
    It amazes me how every one thinks that they can determine what a house needs sight unseen. What works in Florida or Minnesota will not work in Houston. What works in Dallas or Tyler will not work in Houston. Conversely what works in Houston will not work anywhere else.

    Manual J's and other load calc programs are great but will not provide you with the appropriate design or size system only being in the house and asking questions and running a load calc can do this.

    We have houses here in Houston that are 1800 sq.ft. that require 2.5-tons and some that will require 5-tons. The most common problem I find on systems that are properly sized is airflow issues namely lack of sufficient return air capacity and restrictive supply ductwork including cheap plastic grills.

    The OP stated the system cooled sufficiently 3-years ago and now it doesn't cool as well.

    Well let’s see it is much hotter this summer than the past two summers could be relevant. I have found most of the clown techs in this town couldn't properly charge a system if their lives depend on it. I reduce system charge as often as I find systems undercharged.

    To the OP how many return air grills do you have and where are they located are your supply registers plastic. How old is the house just three years or is that how long you have been there. Sounds like it is older since you have different brands of equipment indoor and out. Also is the evaporator coil a Rheem or is it a Tempstar like the condenser. Does the coil have an expansion valve or is it fixed orifice.



  10. #23
    Join Date
    Aug 2004
    Location
    Texas
    Posts
    88
    hiltontech, good luck

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