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  1. #14
    Tech Blue - I would love to know what you are thinking. I will say though that when the 4 ton Goodwin 10 Seer 16 year old unit was working fine (up until the last month) it did cool down my house to the thermostat setting, shut off for a while, repeat. It was in fact meeting the demand. Even when I set the thermostat to 68*. If it was undersized I would guess (and that is ALL it is) that it would never reach my desired temp. My original thinking with the 5 ton was that it would not have to work as hard and therefore would be more efficient and last longer - but that was an incorrect assumption on my part.

    What am I missing?

  2. #15
    r-290 - I was quoted both 5 and 10 year labor warranty for what I felt was a reasonable amount. I do not know if it was manufacturer though...I will follow up on that. Great point.

  3. #16
    Join Date
    Aug 2011
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    16
    UPstateChris,
    I would love to hear from some other techs what they feel about the "rule of thumb"; it is JUST an estimate and maybe totally different depending on climate; The high head pressure could be the simplest factor so far. If your condenser coil is dirty (visibly or not) your system will run at higher "head pressures". If it was working fine before try using a water hose to clean off your condenser coil (just gentle spray to avoid bending the fins) and no chemicals (ask your professional to do that).

  4. #17
    Join Date
    Feb 2007
    Location
    Ohio
    Posts
    205

    Step by step?

    Did you take a temp drop across the evaporator? what is the head pressure/suction temp? are there service valves? can i front seat one to see what happens? can i front seat the other to see what happens? come on man.................................

  5. #18
    Join Date
    Nov 2004
    Location
    SW FL
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    6,295

    Thumbs up

    Quote Originally Posted by Tech Blue View Post

    definitely seems like an issue, and ... I'm wrong but I thought general rule of thumb was 400 sqft/ton of cooling with ... HIGH HEAD PRESSURE!!! ?
    General Rule : 500 to 2,000 sq feet / ton

    High Head Pressure is usually good ...

    It shows THINKING grows the brain.
    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

  6. #19
    Join Date
    Aug 2011
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    [QUOTE=dan sw fl;10993912]General Rule : 500 to 2,000 sq feet / ton

    does that change depending on climate/location and where is that info I'd like to check that out?
    Last edited by Tech Blue; 08-09-2011 at 10:03 PM. Reason: goofed still learning this site

  7. #20
    Join Date
    Dec 2010
    Location
    Down by the river
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    1,664
    Quote Originally Posted by Tech Blue View Post
    Ductwork definitely seems like an issue, as well as heat load; and maybe I'm wrong but I thought general rule of thumb was 400 sqft/ton of cooling with 8' ceilings. You have 12' ceilings and 2700 sqft. hmmmmmmmm. 2700/400=6.75 figure in the high ceilings and high number of windows, french doors etc. ... next step from a 5 ton is 7.5; but I think one key thing is being over looked here. HIGH HEAD PRESSURE!!! What does that usually mean?? could explain why it cools but not very well. Anyone thinking what I'm thinking?
    there's no such thing as ''rule of thumb load calcs. example I have done several houses in the 800ft to ton, have seen scenarios of 1200 to the ton, it all depends on the building envelope.

    my house is at 620 and that was for heating purposes full shade. if I would have just done a/c with gas furnace for heat I would have come in around 930 per ton.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  8. #21
    Join Date
    Nov 2004
    Location
    SW FL
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    6,295

    Hmm

    [QUOTE=Tech Blue;10993952]
    Quote Originally Posted by dan sw fl View Post
    General Rule : 487.6 to 1,918.4 sq. feet/ ton

    does that change depending on climate/location
    and
    where is that info I'd like to check that out?
    Yes & No - it's a general bounding conditons summary that indicates it is - USELESS - to try to address huge differences in climate, building envelope/ age and life style in an overly simplistic manner.

    Of course, there's always going to be some outliers.

    Somebody might think 81'F is a nice , Cool indoor temperature.
    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
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    [QUOTE=Tech Blue;10993952]
    Quote Originally Posted by dan sw fl View Post
    General Rule : 500 to 2,000 sq feet / ton

    does that change depending on climate/location and where is that info I'd like to check that out?
    that there info can be checked out on the manualJ residential load calculation.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  10. #23
    As per the AOP Rules only Professional Members * can reply with
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    Last edited by beenthere; 08-10-2011 at 05:20 AM. Reason: Non *

  11. #24
    Join Date
    Aug 2011
    Posts
    16
    thanks so I'm not crazy after all. I havent had a chance to confirm the manual j but maybe I'm confusing commercial with residential. would you mind sharing where you got your info?

  12. #25
    Join Date
    Aug 2011
    Posts
    16
    Southern Mech,
    I do agree with you it is always a good idea to do a load calc. and like i said originally the rule of thumb was just an estimate

  13. #26
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
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    Thumbs up ACCA J

    Quote Originally Posted by Tech Blue View Post
    thanks so I'm crazy l.

    I havent had a chance to confirm the manual j but maybe I'm confusing commercial with residential.

    would you mind sharing where you got your info?
    Residential @ < 666 sq. feet /ton is Very POOR Practice for a well built house.
    Many thumbs need re-Training and also need to be real versatile.

    My info is based on running 600_+ Manual J calcs.
    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

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