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  1. #1
    Join Date
    Sep 2004
    Posts
    64
    Help, recently replaced 8.5 ton (3 units) with single 5 ton zone system (Amana) Located in Dallas, TX 3200 sq.ft home.
    Home never reaches set temps (always 3-4 degree off), all zones calling for all all day/night long. Contractor has by-bassed air/zone sensors, moved control to thermastats. Now home not taking care of humidity and still not reaching set temps. Now they want to install an addtional 2 ton (3rd stage???)unit.
    I have poor air circulation in one zone and the rooms that do get air sound like a freight train. I do have their load calc's and general data.

    Looking for some suggestions/help. Will answer questions the best I can.

    Thank you all in advance

  2. #2
    Join Date
    Sep 2003
    Posts
    1,311
    Just so I have a better picture of the situation, I perceive that you are the homeowner and this was obviously a remodel. When they installed the zone system did they reuse existing ducts or install new? What is the brand and model # of the zone system?

    Off the bat I see one problem but need a little more info. What was the sensible and latent heat gain numbers?

    You say that they want to install an additional 2 ton unit - how would this be connected to the zone system? With an additional furnace/air handler?

  3. #3
    Join Date
    Sep 2004
    Posts
    64
    Thank you for replying

    Yes I am homeowner and will try my best to answer your questions.

    Show heating load at 89839 BTUH and Cooling @ 53932 Sensible and 7698 Latent or Total 61631

    Hope this is what you wanted?

    Unit is a Amana Prestige Ultra unit, 16 Seer, sorry all I really know.

    They have placed a 14 Seer (2ton) unit outside and have hung the other half above the unit in the attic. They say they are using like the by-pass duct (they removed) when installing it.

    Does this help?



  4. #4
    Join Date
    Sep 2004
    Posts
    64

    Hmm

    Sorry, they also installed all new duct work!

  5. #5
    Join Date
    Sep 2004
    Posts
    64

    Hmm

    Zone controller is made by ZoneX, can't tell who makes the dampers (sorry had to go to attic to find answer)

    Home is a two-story currently set up with 3 zones..

    All second story (zone 3) 13252 Sensible 1530 Latent 14787 total

    Master Suite (zone 2) 9815 Sensible 1856 Latent 11671 total

    Living Area (zone 1) 24164 Sensible 4312 Latent 28476 total

    http://www.zonexsystems.com/

  6. #6
    Join Date
    Sep 2003
    Posts
    1,311
    Eeeeks! I hope that it was a misstatement when they said they are using it like the bypass duct - say 'hello' to problems if that is what they are going to do.

    One problem the system has is inadequate airflow. It will take about 2,800 CFM to extract the 53,932 BTU of sensible heat out of the air conditioner. Nobody makes a residential furnace/air handler that delivers that many CFM. They would have either had to go to a commercial unit or do a "twin" on residential units. If they cannot achieve the proper airflow then they must compensate with more air conditioning but that, too, can only be taken so far. Assuming the blower is putting out 2,000 CFM of air, a 5 ton system will yield only about 39,000 sensible BTU - clearly nowhere close to the heat load calcs. Adding another 2 tons of cooling in a manner like the bypass duct will certainly make the air colder... in fact cold enough to cause the air conditioning coil to ice; Then you'll have very little cooling.

    Another problem that is perceived is that the ducts are not sized properly. This is evidenced by your original statements regarding inadequate airflow, noisy airflow, and combined with the percentage of contractors that actually go through and do duct calculations to determine size. Without properly sized ducts you may end up with continual cooling problems.

    Ok, I've got one more question: Are the pipes all the same size (IE 6") or only two sizes (IE 6" and 8")?

  7. #7
    Join Date
    Sep 2004
    Posts
    64

    Red face

    OK, it's nice to get some real answers.

    From what I can tell there are a comnination of 6" and 8" duct. Some even looks larger then that.

    Let me try to explain the second unit again, just in case. They have the unit being fed by the same return as the 5 ton and then feed it right into the supply duct used by the 5 ton.

    So this is "band aid" fix to a larger issue?

    So your thought is there is not enough air movement? Do the need addtional returns? Our should there be a seperate system (heat and air) to handle one of the zones.


    When I fist started complaining, they came out a blew 6" of insulation in the attic. Didn't seem to do to much?











  8. #8
    Join Date
    Sep 2004
    Posts
    64

    Question

    What do you mean by a "twin" configuration?

    Also, would the indivdual zones effect airflow?

    Also, will this have the same effect on heating my home?

    Thanks again for the help, I feel my contractor is now only looking out for him self and hoping to get through the summer season.

    Again, I hope I expalined the second unit correctly?

  9. #9
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    No way to tell for sure with the info provided, but perhaps they were off on thier load calculation, so dropping from a total of 8.5 tons of cooling to 5 tons left you short on capacity when all zones are calling.
    Just a guess, but they may have figured out they made a mistake, so that is why they want to add the 2 ton unit...

    I don't do any work in Dallas, but I do work in Fort Worth and the mid cities. I can't recall ever seeing a house the size of yours that was built with equipment so oversized that I would drop from 8.5 to 5 tons...

    Have you considdered having an engeneering company come in and do the load calculations and zone layout? There are several in the DFW area that do that sort of work.
    If more government is the answer, then it's a really stupid question.

  10. #10
    Join Date
    Sep 2004
    Posts
    64

    Hmm

    Should have considered that before I contracted the job. Right now I am trying to work through the problem with the installing company and I am in need of information that keeps me on a level playing field with them.

    I think you are right and the agree they undersized the unit. This is why the added the insulation and have even suggested I change out my windows. Not going down that path.

    I am concerned with the extra unit they installed. They are saying it will only kick in as a third stage, after 2nd stage has been running for x period of time.

    The company has been great in responding, I am just tired of seeing them. And I spent a lot of money to upgrade the system and want to make sure I get the proper system config.


  11. #11
    Join Date
    Sep 2004
    Posts
    64

    Thumbs up

    Everyone, I really do apprecaite the information. It is an equalizer for us homeowners. We have focused on the AC side of the system, so is it safe to assume everyone thinks the heat will work (it was a matched Amana heat) fine.

    Right now I am taking everthing you share with me and using it to red between the lines of what they are telling me or doing. Only time will tell.

    Does anyone see any long term problems with the so called 3rd stage design??

  12. #12
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Originally posted by carestx
    Does anyone see any long term problems with the so called 3rd stage design??
    Again, no way to really answer that with certainty without knowing far more about the system. It does sound very odd though.

    You would probably be better served if the added unit took care of a zone by itself, with its own ductwork and all.

    I don't have any experience with the equipment or the zone system they used in your house. All of my experience is with Trane, Lennox, EWC and Honeywell.
    If more government is the answer, then it's a really stupid question.

  13. #13
    Join Date
    Feb 2003
    Posts
    1,996
    You seem to have a large home with a large cooling load. I'd have been suspicious hearing a single 5 ton unit replacing 8.5 tons of capacity. Zoning 2 floors is very common, but going 3 or more is a very complicated balancing act. A step down to between 7 and 8 tons with 2 seperate systems with two zones off the larger unit seems more logical and simpler to install and maintain. They should to be able to simplifiy the ductwork and isolate one of the zones onto its own supply plenum. I would not let them put the 2 ton in (you might need more) until I saw a plan that would support the new cooling load and ductwork.

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