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  1. #1

    Confused about Bryant Evolution dehumidification algorithm

    We just had a new Bryant Evolution system installed last Monday, and while I'm mostly happy with it, I'm confused about how it decides when to dehumidify, which is to say that I'm wondering if it's functioning properly.

    I have the temperature setpoint at 78 degrees during the day and 76 degrees overnight. Cool to Dehumidify is enabled, with the target RH at 46%. Yesterday morning, after the program had switched to the setpoint of 78, the thermostat was reported a current temperature of 76. When I pushed the right button, the display showed that the current RH was 52% (and then it went up a bit from there from my breathing on it), with the A/C showing as OFF.

    Why was the A/C off? Shouldn't it have been dehumidifying? The temperature was less than 3 degrees below the setpoint, and the RH was 6 percentage points above the target.

    I checked the readout again a little later. With current temperature at 77, the A/C now showed DEHUMIDIFY, as I'd have expected.

    Did I have a misconception of how the dehumidification was going to work, or is the unit not functioning properly? In general, I've noticed that the RH often gets away from the 46% target, which I hadn't anticipated prior to the installation. I thought the unit would try to keep the RH right around the target the same way it tries to keep the temperature at its own target.

    The system is perfectly capable of maintaining 46% RH, but it's choosing not to.

  2. #2
    Join Date
    Jan 2004
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    PA
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    68,793
    Probably because the temp was below set point temp.
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  3. #3
    Quote Originally Posted by beenthere View Post
    Probably because the temp was below set point temp.
    I thought that Cool to Dehumidify would function up to 3 degrees below the setpoint. And it did function at 1 degree below. Isn't that supposed to be the difference between Dehumidify=OFF and Dehumidify=ON?

  4. #4
    Join Date
    Jun 2008
    Location
    phoenix az
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    24
    Quote Originally Posted by LooseOnTheLead View Post
    I thought that Cool to Dehumidify would function up to 3 degrees below the setpoint. And it did function at 1 degree below. Isn't that supposed to be the difference between Dehumidify=OFF and Dehumidify=ON?
    Dehumidify function on the evolution system will only run for 10-20 at a time cant remember which. Reason for that is that running in dehumidify to long will cause the indoor to freeze up. After the 10-20 min it will stop and restart after again a predetermined amount of time if the rh is still higher than rh set point.

  5. #5
    Quote Originally Posted by hvacguru69 View Post
    Dehumidify function on the evolution system will only run for 10-20 at a time cant remember which. Reason for that is that running in dehumidify to long will cause the indoor to freeze up. After the 10-20 min it will stop and restart after again a predetermined amount of time if the rh is still higher than rh set point.
    That sounds like a good, authoritative answer. I can't say that I understand why it should freeze up while dehumidifying when it doesn't freeze up otherwise, but that probably has something to do with my total lack of HVAC training. Thanks.

  6. #6
    Join Date
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    Quote Originally Posted by LooseOnTheLead View Post
    I thought that Cool to Dehumidify would function up to 3 degrees below the setpoint. And it did function at 1 degree below. Isn't that supposed to be the difference between Dehumidify=OFF and Dehumidify=ON?
    Make sure the control didn't gt set to a 2 degree limit.
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  7. #7
    Quote Originally Posted by beenthere View Post
    Make sure the control didn't gt set to a 2 degree limit.
    Oh. I haven't noticed that option, but I haven't been looking for it. Do you know where it's located? I do know about the 10-second Advanced menus, so you don't have to explain that aspect. I just didn't see the option you're talking about while I was in them.

  8. #8
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    Don't know where it is on that control.
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    How many times must one fix something before it is fixed?

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