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  1. #1
    Join Date
    Apr 2016
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    Duct sizing / residental HVAC replacement mess - how to size or how to know PROs can?

    First let me say I do understand this is not DIY place.

    I am a small business owner in a service field and I understand very well where all this comes from; no argument with it except...

    Well here's the situation:

    Some 6 or so years ago the single 5 ton split compressor for my 1 story 2400 sqft HVAC house failed.

    If I knew then what I know now I would have found a Mexican to replace the compressor only for 1/4 the price, but I did not.

    I called licensed HVAC pro from the area.

    They talked me into replacing furnace and ducts along with compressor. To be frank there are some good arguments for that too, especially if you have the money and I did.

    Ever since then the three rooms that look west and which happen to be furthest from the furnace, are seriously misbehaving: they are cold in the winter and warm in the summer.

    One of them used to actually be the best room in the house, despite of actually being the furthest; I thought it was because it has a restroom on the west side, so it's actually shielded from the afternoon sun; the other have windows directly facing west and were a bit warmer in summer, but mostly acceptable.

    Now, though, all 3 of them are notably 3-4 degrees off the rest.

    In the winter, when it starts blowing, it is first freezing, then gets warm, but neither as warm nor as strong as the other rooms.

    And when the heater up there stops working, but fan still works, they get back to blowing cold before the fan stops.

    So either there's a leak OR new ducts were not properly sized (and/or insulated).

    I don't think it's a leak, but I'll check. Don't think so because my wife says it's that way ever since HVAC was changed...I just never paid attention and she is more sensitive than me.

    So here's the question...licensed and not cheap HVAC provider was here. I did what they asked and they got paid.

    It just so happens I called them for a different (commercial) job later and they failed it...had some issues there, but each side eat their loss and no major problem has happened....but I am fairly convinced that after paying them IF I had called 2 months later to tell them the above problem they would NOT have changed the ducts.

    Don't trust me, just assume they would have come up with all kinds of explanations, but would not have done it.

    So what is an owner to do in this case?

    I care about resolution of a problem, not about revenge.

    How do I pick a vendor that I know will do better?

    My business side says I should simply not pay until I am happy.

    But you professional guys do not work that way; you want payment when job is complete.

    It is not an option.

    So please do not get offended if I ask DIY questions...of how to verify if the ducts have been properly sized.

    Which is more or less how do I design HVAC, even if only for the purpose of proofing and fixing it.

    Either that or tell me how to make it so that it is not a roll of a dice again.

    because I just made another post - this time with the solution - to another problem that brought me to the site and for the VERY same reason - something had to be fixed after installed by pros.

    I just learned enough to diagnose it and do the fix, only I paid someone to do the fix as space was tight and I was afraid to do my first metal cutting and duct attachment in a very tight space.

    Point still valid though...experience shows I should NOT simply trust offense meant to anyone in particular.

  2. #2
    Join Date
    Nov 2006
    Athens, Ohio
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    There is a link in my sig for locating site members. We are here because of our interest in the trade.

    Or this site to locate techs with specific training in Ning in such areas as air balanacing, system performance, and combustion analysis.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator:

    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  3. #3
    Join Date
    Aug 2002
    Southold, NY
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    You seem to have a few 5-Ton units?
    Quote Originally Posted by kolevbg View Post
    I came to the site for a different problem, but I found this old thread and wanted to give the resolution to whoever may stumble across the same issue.

    So as was to be expected there was nothing grand and mysterious about the issue - it was insufficient return.

    Since it wasn't sufficient it was building negative pressure and the condensation, instead of dripping outside of the unit, was building up until it was getting high enough to start running down the cooled air channel down to the building.

    Adding two extra returns solved the leaks for good.

    What I wanted to say to all the advocates of the "against DIY" and "professional only" principles is this: the problem here is that your professional brothers simply fail to live up to expectations. And expectations are not over the limit unless you consider condensate draining through ducts to be normal.

    It is not that we owners - me in my case - want to save money and deprive you of your right to earn some.

    it is that way too often you - as a professional society - simply fail to deliver.

    So we're simply forced to either be DIY or risk be made fools by just the next one who comes, takes money, and at best doesn't solve the problem, at worst introduces a new one.

    My return to this site for a similar problem is just another proof of that...I am just about to post it.
    they corrected that issue let them at the new issue!

  4. #4
    Join Date
    Aug 2009
    Beatrice, NE
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    In order to properly install a new duct system one must do a proper load calculation. If that was not done then all bets are off on what you got. If the load was not done then the 5 ton unit you put in may not be the right size. The duct may be sized correctly but not for the material they used, example flex moves roughly 20% less than metal, or may not have been installed correctly. One final thought is just because someone is licensed and gets paid for their work does not mean that they are actually qualified to do the job. This is a prime example.

    Sorry for your troubles.

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