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  1. #1
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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 pros...no offense meant to anyone in particular.

  2. #2
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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.
    https://www.myhomecomfort.org/
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    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
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    You seem to have a few 5-Ton units?

    https://hvac-talk.com/vbb/showthread...ng-water/page2
    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
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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.

  5. #5
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    You seem to have a few 5-Ton units?

    https://hvac-talk.com/vbb/showthread...ng-water/page2


    they corrected that issue let them at the new issue!

    Just to be clear they did not correct any issue - I did.

    I learned enough to understand what was going on and why and called someone with simple instruction to add two more returns.

    (which may have been too much; I am not saying I did it by the book).

    My impression as a small commercial building landlord is that most of the techs you call are not good for what they do.

    With luck their experience helps, but that same experience also often prevents them to look outside of their comfort zone.

    Most of the young ones will promise everything, hack something and leave.

    You would have thought that it can't go wrong replacing existing system - all vents remain the same, tubing needs replacing, new furnace and new compressor, but same tonage...I mean it is copy and paste.

    Apparently not.

    And now I don't know what the original was, so I need someone to measure and correct it without breaking the wallet.

    But it's not breaking the wallet that bothers me; it s that if I do not have way to control the outcome then I am not doing it any better than the first time.

    So guys, it may be unusual question, but how do you hire a HVAC specialist in a way that guarantees they won't leave with poorly working system?

  6. #6
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    Quote Originally Posted by kolevbg View Post
    Just to be clear they did not correct any issue - I did.

    I learned enough to understand what was going on and why and called someone with simple instruction to add two more returns.

    (which may have been too much; I am not saying I did it by the book).

    My impression as a small commercial building landlord is that most of the techs you call are not good for what they do.

    With luck their experience helps, but that same experience also often prevents them to look outside of their comfort zone.

    Most of the young ones will promise everything, hack something and leave.

    You would have thought that it can't go wrong replacing existing system - all vents remain the same, tubing needs replacing, new furnace and new compressor, but same tonage...I mean it is copy and paste.

    Apparently not.

    And now I don't know what the original was, so I need someone to measure and correct it without breaking the wallet.

    But it's not breaking the wallet that bothers me; it s that if I do not have way to control the outcome then I am not doing it any better than the first time.

    So guys, it may be unusual question, but how do you hire a HVAC specialist in a way that guarantees they won't leave with poorly working system?
    Now that is the $64,000 question isn't it. How do you hire any profession and know that you are getting what you are suppose to. If a person can come up with that formula you could sell it for millions, and you may create a standard that companies would try to model for more customers. Sadly greed is going to win more times than not. Human nature is that we want the most for less. That street runs both ways. Customers want the most for the least, most companies want the most money for the least work. That sets us up for failure on a grand scale. There are a few companies that just want to do the job right. They know you need to do X,Y, & Z for the job to work properly and they refuse to leave any of those steps out. I would venture to guess if you hired most of the companies represented on this site you would get the type of job you want, you just may not like the price as well.

  7. #7
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    Quote Originally Posted by BNME8EZ View Post
    Now that is the $64,000 question isn't it. How do you hire any profession and know that you are getting what you are suppose to. If a person can come up with that formula you could sell it for millions, and you may create a standard that companies would try to model for more customers. Sadly greed is going to win more times than not. Human nature is that we want the most for less. That street runs both ways. Customers want the most for the least, most companies want the most money for the least work. That sets us up for failure on a grand scale. There are a few companies that just want to do the job right. They know you need to do X,Y, & Z for the job to work properly and they refuse to leave any of those steps out. I would venture to guess if you hired most of the companies represented on this site you would get the type of job you want, you just may not like the price as well.
    I disagree.................

    We charge too much!

    Love the fact he comes here.......... denies we helped but goes in the direction pointed then claims HE fixed it!

    Yep We Charge Too Damn Much!

  8. #8
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    Quote Originally Posted by pecmsg View Post

    I disagree.................
    We charge too much!
    Love the fact he comes here.......... then claims HE fixed it!
    Yep We Charge Too Damn Much!
    THAT has a VERY EFFECTIVE Solution.

    ALL Your misappropriated funds should be promptly Directed to my PayPAL account.
    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. #9
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    Quote Originally Posted by pecmsg View Post
    I disagree.................

    We charge too much!

    Love the fact he comes here.......... denies we helped but goes in the direction pointed then claims HE fixed it!

    Yep We Charge Too Damn Much!
    I did say "most" not all, I was thinking of you when I wrote it.

  10. #10
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    I disagree.................

    We charge too much!

    Love the fact he comes here.......... denies we helped but goes in the direction pointed then claims HE fixed it!

    Yep We Charge Too Damn Much!
    See that is the type of response that makes me doubt that "any company I pick from this site" (per another post) will do the trick.

    If someone here helped me find the right answer the first time it is escaping me.

    I do not know what "static pressure" is and I am not aware of a single response back then which has made up my mind; it's not like it was a one time event that helped me solve it either - it took about 2 months of eliminations until I eventually discovered 2 things that convinced me it was a pressure problem: first, then AC stopped working and fan stopped blowing the RTU would start leaking water on the roof like crazy; If I had seen that earlier maybe I would have figured it out sooner; and second, when I built a wall inside the RTU which would allow water to collect longer before starting to go in, the leaking stopped - apparently it was for long enough to allow the AC to naturally stop cooling and for the collected water to drain out.

    So clearly it was pressure problem and clearly the apparent way to resolve it was to allow more return.

    NOTHING in the past responses made that clear or convincing to me.

    "Find someone who knows static pressure" does not even come close.

    No offense meant, this is how I see things.

    Feel free to feel like you've provided the answer, no feelings will be hurt on this end.

    But comes to illustrate why I am reserved to input I receive, be it in place like this forum.

  11. #11
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    Don’t know what Static Pressure means but claim we’re all incompetent overcharging crooks

    I am paraphrasing but that’s the way us knoladgeble technations take your reply’s.

    Try a Google search
    Static
    Pressure
    TESP
    mr know it all!

  12. #12
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Don’t know what Static Pressure means but claim we’re all incompetent overcharging crooks

    I am paraphrasing but that’s the way us knoladgeble technations take your reply’s.

    Try a Google search
    Static
    Pressure
    TESP
    mr know it all!
    If you do your job with the accuracy of your written statements I most definitely would not want to hire you :-)

    Stopping here, you've presented your point and so did I.

    Doesn't have to get personal and in my view, after reading it, I did not start it.

    Thanks to everyone who tried to help, whether I got them right or not :-)

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