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  1. #1
    Join Date
    May 2004
    Posts
    12
    I have a 3 zone system in my house. When one zone is working, air flow is really good. When the next two zones turn on, air flow drops dramatically and if all three zones are open, there isn't sufficient air flow to cool all zones.

    Here's what I think. When only one zone is open, the damper in the bypass duct opens because of excessive air pressure. But, when the other two zones turn on, it may take a while for the bypass damper to close. Therefore, a lot of cool air is circulating in the AC unit rather than through my house.

    When the zoning was originally installed, there was a counter weight on the bypass damper. However, the service tech removed it several days after installation saying that we didn't need it.

    I believe that because there's no counter weight, it may take time for the bypass damper to close when all zones are running, therefore, air flow is deminished.

    Does this make sense or am I full of s*?

  2. #2
    Join Date
    Jun 2004
    Location
    New Jersey
    Posts
    23
    It's the counterweight that opposes the air pressure in the bypass duct and closes the bypass when no pressure is present. Without the counterweights the bypass will be open whenever there is pressure in the bypass duct. Which is the path of least resistance for the air whenever the blower operates. Try manually closing the bypass damper. Mover the handle (that use to hold the weights) to a position perpendicular to the bypass duct. Use duct tape to keep it in this position if necessary. Then turn the fan switch at the thermostat fron AUTO to ON and see if that improves your air flow.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by l_kent_a
    I have a 3 zone system in my house. When one zone is working, air flow is really good. When the next two zones turn on, air flow drops dramatically and if all three zones are open, there isn't sufficient air flow to cool all zones.

    Here's what I think. When only one zone is open, the damper in the bypass duct opens because of excessive air pressure. But, when the other two zones turn on, it may take a while for the bypass damper to close. Therefore, a lot of cool air is circulating in the AC unit rather than through my house.

    When the zoning was originally installed, there was a counter weight on the bypass damper. However, the service tech removed it several days after installation saying that we didn't need it.

    I believe that because there's no counter weight, it may take time for the bypass damper to close when all zones are running, therefore, air flow is deminished.

    Does this make sense or am I full of s*?

    You're hired!!Call that tech tell him"you are the weakest link,Good Bye!!

    Bypass dampers are oftened sized too large,if so it is difficult to get them to work correctly with the weights.

    Tell us the tonnage,damper and bypass sizes.to see if they are close to what they should be.

  4. #4
    Join Date
    May 2004
    Posts
    12
    Thanks for the feedback.

    I'll try closing the bypass duct this weekend.

    By the way, I have a variable speed fan unit so maybe the fan unit will be smart enough to slow down if there's too much pressure.

  5. #5
    Join Date
    Jun 2004
    Location
    New Jersey
    Posts
    23
    It works the other way around. As the pressure increases, the blower will speed up to overcome the increase. So if your bypass is open, then the blower doesn't see any pressure to overcome because all of the air is bypassing. Also check your circuit board on the blower. Often there is a DIP switch that must be set to let the blower know that there are zones that will vary the system resistance from time to time.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,928
    You need the weight, and never let that tech touch it again.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    kent,

    Was that "prodiyer" that was out there??

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,274

    Exclamation What the H_ _ _ .

    Originally posted by l_kent_a
    When the zoning was originally installed, there was a counter weight on the bypass damper. However, the service tech removed it several days after installation saying that we didn't need it.
    That SORRY little service tech KNOWS about sabotage,
    but not by-pass function.

    QUITE SIMPLY:
    Restore the weights to the by-pass damper.
    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
    Join Date
    Feb 2003
    Location
    South Carolina
    Posts
    1,333
    he dont know much about zones.

  10. #10
    Join Date
    Nov 2002
    Location
    Central Florida
    Posts
    655
    Apparently the tech didn't know how a barametric damper operates. If the counter weight isn't there, the damper is "blowing in the wind."
    Most of the time it's not what you know, It's knowing where to find it!

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