Am I dealing with ding-dongs?
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  1. #1
    Join Date
    Jul 2008
    Posts
    4

    Am I dealing with ding-dongs?

    I've got a 11 year old house with dual 4 ton units (up/down config), and the upstairs has failed needing thousands in repairs. Thinking at that age I may do better to replace the units than repair, I've called in two people for estimates. I also have complaints that the upstairs has never kept up on hot days or kept the floor evenly cooled.

    First guy quoted new everything, upgrading the upstairs from 4->5 ton. Of note he didn't recommend any more vents or returns (I had a return question, so I asked specifically).

    Second guy is sending me two options in writing tomorrow, one with new everything, the other reusing the existing furnace, just new AC. Also a 4->5 ton upgrade. He noted there were not enough returns and quoted adding one, and noted the outside copper pipes were not big enough for a 5 ton high efficiency unit, so he quoted upgrading those.

    The return thing got me looking, so I've found a lot of things online with "rules of thumb" for both return and supply sizing and it appears to me the downstairs (still running, keeps the floor comfortable) has returns matching the 100inch per ton return sizing (barely) and a similar number of outputs, but the upstairs is more like 320 sq in return, and 340 of supply (based on straight round pipe size, not accounting for runs/bends).

    So I'm thinking the problem upstairs is not 4->5 ton, but rather lack of returns and supplies. Also, just upgrading without more returns and supplies seems like a bad idea if they are already marginal.

    It seems to me both of these guys should have measured and counted all returns and supplies before quoting complete system swap outs. Am I dealing with ding-dongs or is that just not normal practice? Is it worth specifically asking for someone to do the calculation, and if so do I want someone independent to do it? How do I find such a person?

  2. #2
    Join Date
    Jun 2008
    Location
    Phoenix, AZ
    Posts
    70
    most of the estimaters I've seen are more salesmen than install/service tech. If there is a major error in the duct sizing of the unit, then a service technician should be able to tell just by looking at the pressures, superheat, subcool... I would find someone... a technician, who's experienced in duct design/sizing. Find out what's really wrong before you put in the wrong unit and or incorrect duct work...

  3. #3
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by dj3901783 View Post
    most of the estimaters I've seen are more salesmen than install/service tech. If there is a major error in the duct sizing of the unit, then a service technician should be able to tell just by looking at the pressures, superheat, subcool... I would find someone... a technician, who's experienced in duct design/sizing. Find out what's really wrong before you put in the wrong unit and or incorrect duct work...
    I'm sure the readers would like to know your location and size/layout of your home. That's a lot of tonnage.

    AM

  4. #4
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Quote Originally Posted by bicknell View Post
    I've got a 11 year old house with dual 4 ton units (up/down config), and the upstairs has failed needing thousands in repairs. Thinking at that age I may do better to replace the units than repair, I've called in two people for estimates. I also have complaints that the upstairs has never kept up on hot days or kept the floor evenly cooled.

    First guy quoted new everything, upgrading the upstairs from 4->5 ton. Of note he didn't recommend any more vents or returns (I had a return question, so I asked specifically).

    Second guy is sending me two options in writing tomorrow, one with new everything, the other reusing the existing furnace, just new AC. Also a 4->5 ton upgrade. He noted there were not enough returns and quoted adding one, and noted the outside copper pipes were not big enough for a 5 ton high efficiency unit, so he quoted upgrading those.

    The return thing got me looking, so I've found a lot of things online with "rules of thumb" for both return and supply sizing and it appears to me the downstairs (still running, keeps the floor comfortable) has returns matching the 100inch per ton return sizing (barely) and a similar number of outputs, but the upstairs is more like 320 sq in return, and 340 of supply (based on straight round pipe size, not accounting for runs/bends).

    So I'm thinking the problem upstairs is not 4->5 ton, but rather lack of returns and supplies. Also, just upgrading without more returns and supplies seems like a bad idea if they are already marginal.

    It seems to me both of these guys should have measured and counted all returns and supplies before quoting complete system swap outs. Am I dealing with ding-dongs or is that just not normal practice? Is it worth specifically asking for someone to do the calculation, and if so do I want someone independent to do it? How do I find such a person?
    Ding dongs, yes!

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Manual J,S,and D ,are what need to be done.Call until you find a contractor that can/will do these.


    www.acca.org is where these are from

  6. #6
    Join Date
    Jul 2008
    Posts
    4
    Sadly, finding someone willing to do the work is proving difficult. I've now had two people tell me I didn't need all that. *sigh* It's frustrating to want to pay someone to do it (I'd rather spend a couple hundred on figuring out the right size, than $10k on a wrong sized system) and not be able to find them.

    I'll keep hunting.

  7. #7
    Join Date
    Sep 2003
    Location
    Western PA
    Posts
    1,354
    What's your location? Maybe one of the professionals on this site can help you.

  8. #8
    Join Date
    Jul 2008
    Posts
    4
    Suburb of Memphis TN. If anyone knows of a competent HVAC guy, I'm all ears.

  9. #9
    Join Date
    Feb 2008
    Location
    Dallas & Longview, TX
    Posts
    629
    I just purchased the HVAC Calc program so I could do my own. I have the same problem as you regarding finding people willing to spend the time to do it right. You can click on the link at the top of the page and download a trial version to see it.

    The size of the ducting per the tonnage as you mentioned, is only one part of doing it right. Finding out if you need to upsize or not is another part. Alot of if not most new installs are oversized systems running through undersized ductwork.

  10. #10
    Join Date
    Apr 2007
    Posts
    623
    I WOULD LIKE TO CONGRATULATE EVERYONE, INCLUDING MYSELF. For clicking on something on the internet, that had the word ding-dongs in it.

  11. #11
    Join Date
    Aug 2004
    Location
    Balt/Wash
    Posts
    214
    Quote Originally Posted by aintitfun View Post
    I WOULD LIKE TO CONGRATULATE EVERYONE, INCLUDING MYSELF. For clicking on something on the internet, that had the word ding-dongs in it.
    MMMMNNNN ding dongs MmmmNmmm

  12. #12
    Join Date
    Dec 2006
    Location
    Northern VA
    Posts
    389
    Quote Originally Posted by eglide99 View Post
    MMMMNNNN ding dongs MmmmNmmm
    Me too.. I clicked on it cause I was hungry ....

  13. #13
    Join Date
    Jun 2008
    Location
    Florida
    Posts
    26
    GREAT!!! Now I have to go to the store and get some ding dongs or ho-ho's and a mountain dew.

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