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  1. #1
    Join Date
    Nov 2007
    Posts
    47

    Unhappy Continuing issues with Vision Pro IAQ

    Some time ago I started a thread about issues I was having with my new Honeywell Vision Pro IAQ thermostat. At the time, the issue was with humidity sensing accuracy and smoothness when in humidify mode (in the winter). Basically, the symptoms were that the reported humidity was quite low (compared to references including a Vision Pro 8000 placed on the same wall), and also tended to stay fixed for a long time and then suddenly "jump".

    Due to the issues I was having, my dealer replaced the unit. The new one had the same offset issue, but didn't seem to suffer from the "jumping" problem. Since I could correct for this behavior by adjusting my setpoint, I left things alone.

    Now it's summer, and I'm experiencing issues which are disturbingly familiar. The reported humidity continues to be 4-10 points lower that what my two reference sensors (both within 6 inches of the IAQ and both in good agreement with each other) report. More disturbingly, I'm seeing the same kind of sudden jumps, not just in reported humidity but also in reported temperature!

    Today, because my humidity was higher than I'd like (around 61% according to the meters I trust), I lowered the dehumidify setpoint on my stat from 50% to 45% to make it kick on (it was reporting 55%). At the time I made this setting change, the stat was reporting a temp of 78F (which is my setpoint), and my references agreed to within 1 degree F.

    Roughly two hours later, I noticed that the system had been running a *long* time and that I was feeling quite cold. The IAQ was still reporting 78F. The other devices were reporting 74-75!

    I immediately changed my dehumidify setpoint back to 50%. When I hit 'Done' and returned to the main screen, the reported temp on the stat instantly changed to 76F!

    These thermostats are supposed to have pretty good accuracy... certainly better than 0.5 degree, right? There's absolutely no way it should jump 2 reported degrees that fast.

    [EDIT: After composing the initial version of this message, I went down to look at the thermostat(s) again. My references both read 75, but now the IAQ is back at 78. Arrgghh!]

    I'm really not sure what to do, here. This kind of problem is extremely hard for a tech to observe in action -- it's not as if I can make this happen at will. I can confidently predict that my dealer will be... grumpy, if I tell him this thermostat is once again not working.

    I'm really hoping that someone here has a close enough relationship with Honeywell that they can help me solve this. I was very happy with my Vision Pro 8000 (the one I'm now using as one of my control references), and I've always had a good impression of Honeywell products but... this is ridiculous. Help!
    Last edited by dbb1; 06-06-2008 at 08:32 PM. Reason: new data

  2. #2
    Join Date
    Nov 2007
    Location
    Tucson AZ
    Posts
    166

    Thermostat lies!

    I have a Trane TC803 (Honeywell) thermostat and have been monitoring it with a digital thermometer that displays to the nearest tenth of a degree.

    What I have observed is that the thermostat will report that it is at the setpoint as long as it is within a couple of degrees of the setpoint. If I make a change to the setpoint of five or more degrees then the thermostat will accurately display the actual temperature, which could be a couple of degrees different than the previous setpoint.

    Looks as though Honeywell decided to have the thermostat tell a little white lie just to make the HO believe the temperature was holding exactly to the setpoint.

  3. #3
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Where is your stat located? Do you have a remote sensor?
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    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  4. #4
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,665
    is the hole that the tstat wires come through sealed

  5. #5
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by catmanacman View Post
    is the hole that the tstat wires come through sealed
    excellent point.

    I didn't mention it first. That was to come later.

    Another......is the stat at any time in direct sunlight or near an exterior door or window?
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  6. #6
    Join Date
    Jan 2008
    Posts
    91
    Quote Originally Posted by jeff520 View Post
    I have a Trane TC803 (Honeywell) thermostat and have been monitoring it with a digital thermometer that displays to the nearest tenth of a degree.

    What I have observed is that the thermostat will report that it is at the setpoint as long as it is within a couple of degrees of the setpoint. If I make a change to the setpoint of five or more degrees then the thermostat will accurately display the actual temperature, which could be a couple of degrees different than the previous setpoint.

    Looks as though Honeywell decided to have the thermostat tell a little white lie just to make the HO believe the temperature was holding exactly to the setpoint.
    I also have the 803. Hole in the wall is sealed, no direct sun, central location in house. I see the exact same thing happen. I just chalk it up to one of those nuances.

    What's funny, is that you know these stats can accurately read temp and humidity, otherwise its adaptive recovery features would not work so well. I wonder who at Honeywell decided that it would be better for the customer's peace of mind to "adjust" the display in this way.

  7. #7
    Join Date
    Mar 2008
    Location
    Houston, Texas
    Posts
    352
    This was discussed earlier in a previous post. The stat doesn't display the most accurate temp at all times depending on several things, just as you stated. It will also allow the system to run longer to remove humidity and it won't alarm you to it accually being colder than your setpoint.

    Some people see this as a problem, I don't.

    IMO you shouldn't be looking at the stat that closely. Once you accept that as "normal" it is no longer a problem.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,117
    Couple years back, and it wasn't an IAQ stat.
    Had a customer that complained the stat was not acturate.

    After several calls about it. Finally found that the stud bay behind the stat had a 5" oval running to the powder room floor register.
    When it was closed no problem. When the floor reg was open, the cavity would warm up enough to shut the stat off early.

    Just something to check.
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  9. #9
    Join Date
    Nov 2007
    Posts
    47
    Thanks to all who replied.

    iraqveteran, catmanacman: The stat is near the corner of two inside wires, not exposed to sunlight or directly in the path of a vent. Last winter I sealed the opening behind it with some of that non-hardening putty. I do have an external sensor, which is on a separate cable per Honeywell's instructions.

    Skip 2 my lou: I agree there's no point in obsessing over the behavior of the thermostat too much. My original problem (during the winter) was that the stat would continue to humidify the house *way way way* beyond what it should. I would come back to the house after being gone for a few hours to find the windows all fogged up, etc. This behavior started my... obsession with monitoring the stat.

    Since I do have it configured to allow up to 3 degrees overcool, I guess it isn't surprising that it ran for so long and cooled that far below the setpoint. I was surprised by the fact that the temp display didn't change... silly me.

    I guess I'll continue to keep an eye on it, but perhaps from a higher-level perspective, rather than monitoring the actual display.

    I agree with Cub... what a strange design decision for Honeywell to make. Really bugs the @$@%$ out of engineer types like me.

  10. #10
    Join Date
    Nov 2007
    Posts
    47
    Quote Originally Posted by beenthere View Post
    Couple years back, and it wasn't an IAQ stat.
    Had a customer that complained the stat was not acturate.

    After several calls about it. Finally found that the stud bay behind the stat had a 5" oval running to the powder room floor register.
    When it was closed no problem. When the floor reg was open, the cavity would warm up enough to shut the stat off early.

    Just something to check.
    I'll doublecheck, but I don't believe any ductwork is behind my wall. Also, it's summertime now, but my IAQ stat is reading *higher* temperatures than the two reference sensors (which are within 6 inches of the IAQ, but *not* mounted to the wall). If I had a problem of the type you describe, I'd expect the cavity to cool off the stat and shut it off early, rather than keep it running too long.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,117
    In cooling mode it should be cooler if its caused by a duct. Unless its caused by that cavity being a return.

    Does the other side of the wall have direct sun light.
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  12. #12
    Join Date
    Mar 2008
    Location
    Houston, Texas
    Posts
    352
    [QUOTE=dbb1;1882868]Thanks to all who replied.

    I do have an external sensor, which is on a separate cable per Honeywell's instructions.

    also make sure that your sensor wires a twisted, however odd this seems, it makes a difference. I generally use 18/3 wire, stretch the length disired, and put it in you corless drill to twist it. Shielded wire can also be used, but not needed in all cases.

  13. #13
    Join Date
    Nov 2007
    Posts
    47
    Quote Originally Posted by beenthere View Post
    In cooling mode it should be cooler if its caused by a duct. Unless its caused by that cavity being a return.

    Does the other side of the wall have direct sun light.
    There is a main return about 3-5 feet to the left of the stat... it certainly could (and probably is) leaking air into the space. Still, I'm pretty sure I've blocked all direct airflow out of the hole behind the stat, so if it's having an effect it would have to be through radiative means only....

    The other side of the wall does not have sunlight. The stat is on a wall that divides two interior rooms.

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