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Thread: Zoning problems

  1. #1

    Zoning problems

    We have a 2 story house, one a/c unit, 2 zones. Our house was built in 2009 and we've had problems with our a/c unit and zones before we even closed on the house. We continue to have zoning system problems and we can't get it resolved. The dampers have already been replaced many times (at least 5x each) the damper motors have been replaced, the zoning board has been rewired 2x. We constantly have to call the a/c company out to have them replace a damper or rewire a damper or rebalance the air because the master and kids rooms are burning hot, the game room freezing. When they "fix" the air flow the kids room are like loud air tunnels and they can't sleep.

    I don't know who to contact to help us. I feel like the a/c company we've been using is just putting band-aids on things until our warranty is up. I want to figure out WHY the dampers keep breaking and the air flow is constantly screwed up. Who should I contact? What could be a possible problem - maybe a desing flaw???

    Any help and suggestions are appreciated.

    Amber

  2. #2
    Join Date
    Jun 2011
    Location
    Wake Forest, NC
    Posts
    352
    Two things come to mind:

    1. If there are too many dampers on the system the transformer supplying power to the zone board and damper motors will not have the power to operate the motors properly. If it is a Honeywell zone system (that is the only one I know well enough to be able to speak on right off the top of my head) The board draws 10 VA and each damper draws 6 VA. Count the number of dampers on the system, multiply that number by 6 then add 10 for the zone board. If you can find the transformer that operates the system it will have a VA rating on the sticker on it. Most are either 40 VA or 75 VA. If the total you get is higher than the VA rating on the transformer that could very well be the cause of the dampers not operating properly. If that is the case you will need to have the transformer that supplys the zone system upgraded to a higher VA rating.

    2. The loud wind noise you hear in some rooms is because only one zone is operating at that time. When that happens it forces all the air from the total of the system into the one zone, thus increasing air velocity above the recommended amount to prevent air velocity noise. The best solution for that scenario is a bypass damper. A bypass damper opens when only one zone is operating and recirculates air from the supply plenum back to the return plenum. This lowers air velocity which reduces noise, and also lowers the static pressure of the system when operating with only one zone. Keeping the static pressure down will prolong blower fan and compressor life. Also, if the system is a furnace, without a bypass damper you may have the high temperature limit switch interrupt furnace operation as the discharge temperature of the furnace rises above safe levels due to restricted air flow.

    I do not know who in your area to recommend, maybe someone else here can help, but use some of the information here to help you screen out contractors when you call them. It will help you to find ones that really understand zoning systems versus the ones that just replace damper motors when they dont operate properly.

    Hope this helps.
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

  3. #3
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    Some specifics would be helpful so we can try and provide some good guidance without using a shotgun approach. You may need to ask your AC techs for a few of these answers.

    1. The Manufacturer of the zone system.
    2. The type of dampers installed (pneumatic, electric, powered open/powered closed, powered open/spring closed, etc.)
    3. The method of static relief (by-pass damper, dump zone, modulating dampers)
    4. The capacity in CFM of each zone.
    5. The model numbers of both the indoor and outdoor units, along with the manufacturer of those units.

    You should also have or obtain a copy of the load analysis used to design the zone system.

    If the installing company did anything other than guess at the loads, then they should have the load analysis that's absolutely necessary to design a proper zoned air system.

    The pros on this site can make a lot of guesses but that's about all we're doing. You can keep going back to the AC company but it sounds like they're also just patching holes. In order to bring some solid relief to you and end up with a system that operates as anticipated, the above information is needed.

  4. #4
    Join Date
    Jan 2008
    Posts
    1,958
    From the limited description, it sounds like a poorly designed system.
    All the "repairs" in the world won't fix it unless things are designed and installed properly.
    Zoning can be very difficult and costly to operate in the hands of the in-experienced.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  5. #5
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    HVACTechNC, solid advice

    How about the quality of the power? or bad ground. You seem to have some good insight in this. How often is the power the culprit?
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  6. #6
    Join Date
    Jun 2011
    Location
    Wake Forest, NC
    Posts
    352
    The most common problem with power being a culprit on a zoning system that I have seen is when zoning is added after the fact. Typically if a system is to be zoned from design and install then each zone will feed off a supply cube that is fed by a single trunk (i.e. a 3 zone system where each of the three zones is built off a cube supplied by say a 12 in flex or 14 or w.e.) With this design you can run all three zones off of three dampers... Very easy, very straightforward, no worries on the low voltage power side. When a system was installed without dampers, and zoning is added after the fact then often you have multiple runs coming off the supply plenum that must all be dampered to operate one zone... (example would be 1st zone has 6-6" runs directly on the plenum that all need dampers to be zone 1 and then a run of flex to a cube further away to be zone 2.) In this situation the 6 dampers on zone 1 would almost max out a 40VA transformer all by themselves.

    To try to answer your question directly, poor design is much more prevalent than a low voltage power problem. Both are caused by ignorance of damper and zoning systems, but LV power problems only surface when a series of circumstances are in place, where a poor design of the system will produce unsatisfactory airflow whenever the system is on...
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

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