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Thread: Do I need to have my ductwork redone?

  1. #21
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    Look up Manual D
    Quote Originally Posted by mnoone View Post
    Can you please explain where I have made a mistake? Or if there is a good resource on duct planning I'm happy to work my way through that.
    Sent from my SM-G965W using Tapatalk

  2. #22
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    Quote Originally Posted by mnoone View Post
    I'm trying to choose one. That is the problem. Repeatedly telling me to ask a professional is unfortunately not helpful right now as I am trying to *choose* a professional. I recognize that people on this forum are sensitive to DIYers as they represent a loss of business so DIYing is heavily discouraged - but that is not my goal here. I have little interest in doing my own system. I just want somebody to do my system well and for a fair price.
    Then get the duct work redone!

  3. #23
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    This forum is full of homeowners coming here asking for help with a new system that they hate. The complaints on the AC side range from lack of humidity removal, short cycling of the AC, constant service calls for nagging issues that the installer just can't seem to figure out (or admit they cut corners), noisy vents/duct work/equipment, energy bills that they were guaranteed would be less but turned out to be way more than they thought they'd be. If you want to educate yourself about the whole HVAC process then there is no better place to start than reading the tens of thousands of posts here about problems after installations of new systems. The other thing you'll read about is professionals sharing their horror stories about jobs they've been on where someone installed a system/ductwork that was not adequate to meet both the systems needs but also to make the customer happy.

    I appreciate your not wanting to spend more on the job than you believe you need to while getting a system you believe will do everything you need and want it to do. You could always ask the other three contractors to guarantee in writing that when the job is done that you will be 100% happy with everything or they will change/modify things until you are, at no added cost. At least that way you will get a feel how confident they are in the recommendations they're making.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #24
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    Sizing ductwork is based on an accurate ACCA Manual J Load Calculation, this will provide the required CFM per room of the house, in both heating and cooling. The contractor then takes that info into ACCA Manual D to correctly size the ductwork. Go to the contractor locator map on this website and find a contractor in your area, ask them how they size duct. The ACCA Manuals are national standards and defensible in court. You need someone who knows how to do it properly.
    As far as the amount of vents needed, contractor number 4 may be trying to balance the volume of required CFM in order to reduce noise. Have you had this conversation with him? Sit down with him and have him explain it to you.
    Philippians 4:13
    I can do all things in him that strengthen me.
    Apostle Paul inspired by GOD.

  5. #25
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    One thing that home owners do not understand, time.

    I am not talking about how long it takes to do a job, yes there are differences between companies on how long it take to do a job and often the difference in time is the difference between a good job and a great one.

    But again that is not what i am talking about. To get the measurements to do a proper load calc (Man J) takes some time, especially a room by room load which is what needs to be done for a proper duct design. Then you have the time to lay out the duct, figure actual lengths and TEL's, looking at register data to select the right one for the application. Depending on the design of the house you could easily have over 8 hours. I know there have been times I have spent more time looking into the engineering on a job than the company that got the work had on the job doing the install, and yes eventually I would get called back to try and fix it.

    The bottom line is what may not seem like a fair price to you is likely the price that if everything goes right on the job they will make a little money or break even. If the job goes south they will lose money.

  6. #26
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    This is why I do not work with builders or new construction. Too much time up front to do it right that they do not want to compensate for.
    Quote Originally Posted by BNME8EZ View Post
    One thing that home owners do not understand, time.

    I am not talking about how long it takes to do a job, yes there are differences between companies on how long it take to do a job and often the difference in time is the difference between a good job and a great one.

    But again that is not what i am talking about. To get the measurements to do a proper load calc (Man J) takes some time, especially a room by room load which is what needs to be done for a proper duct design. Then you have the time to lay out the duct, figure actual lengths and TEL's, looking at register data to select the right one for the application. Depending on the design of the house you could easily have over 8 hours. I know there have been times I have spent more time looking into the engineering on a job than the company that got the work had on the job doing the install, and yes eventually I would get called back to try and fix it.

    The bottom line is what may not seem like a fair price to you is likely the price that if everything goes right on the job they will make a little money or break even. If the job goes south they will lose money.
    Philippians 4:13
    I can do all things in him that strengthen me.
    Apostle Paul inspired by GOD.

  7. #27
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    Quote Originally Posted by Artietech View Post
    This is why I do not work with builders or new construction. Too much time up front to do it right that they do not want to compensate for.
    This is why my new construction is limited to custom work, I don't do it for nothin'.

  8. #28
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    Quote Originally Posted by BNME8EZ View Post
    Warm air is buoyant, cold air is heavy.
    __________ _ _ _ /\ _ _ /\ _ _ ___ B.S.

    not THE VALID reason that MORE AIR IS REQUIRED FOR COOLING.

    Q = cfm* dT * 1.08 <- Valid Reason
    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. #29
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    Nov 2004
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    Quote Originally Posted by mnoone View Post
    I am getting ready to have a new HVAC system installed in my house. I've had 4 different companies come out to quote the work. Normally I'd have two come out - but I just didn't get a good vibe from the first three. The 4th I actually liked though.

    My house is 1600 square feet and I currently have
    a 30 year old central furnace that works fine
    that is using 60 year old rigid ducting throughout the house.

    First and second vendors want to add a couple new vents (go from 9 to 11), and expand my two 2x14 boots to 4x14 (the rest are 4x14). They also both wanted to increase my return duct from 14" to 16" diameter

    Third vendor wants to tear out all my old rigid ducting and replace it all with flex. Not sure about sizing. Also mentioned adding at least one vent.

    Fourth vendor wants to tear out all ductwork, replace it all (with new rigid), and add 7 vents (go from 9 to 16).

    All of them are quoting ~3-4 ton ACs, and 60-80KBTU furnaces. This is in Northern California.

    The fourth vendor is the only one who took floor plan and ran calculations with some sort of software (didn't catch the name - but some sort of specialized HVAC software). The others seemed to just use some rule of thumb to size furnace and AC.

    So - my questions:

    • Does 16 registers seem like a lot for a 3.5 ton AC?
    • My current furnace works fine (with 14" return and 9 registers). Does it make sense that I would need to enlarge return and add more registers to add cooling?
    • If it does make sense - why couldn't I just enlarge the ductwork going to the vents but not add so many vents? Would it get noisy?
    • What can I do as a homeowner to make sure these guys are sane?
    START OVER:
    _______ So you are trying to add A/C in a 1,600 sq ft N Calif ranch built in 1956.

    1ST: Blower Door Tet required to determine Infiltration.
    _____ AND SEAL THE HOSUE AS REQUIRED.


    2ND: Original Windows ?
    ___ No Wall insulation.


    ZIP _ _ _ _ _

    N Calif might in the millions (or billions) of acres.
    We are only concerned with ONE HERE.
    Attached Images Attached Images
    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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