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  1. #1

    Vision Pro th8000 staging

    Hey,
    I have a 2 stage geothermal system and a vision pro th8000. Does anyone know what allows 2nd stage heat or cool to energize? Is it based on how many degrees off of setpoint? It seems like the stat will run first stage for a long time because the geothermal unit is running at 70% capacity on first stage. I would like to use 2nd stage sooner to cut down on run time, but I don't think this stat is capable of adjusting the staging.
    Thanks!

  2. #2
    Join Date
    Oct 2004
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    Central WA
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    There is a lot of math buried in that thermostat that controls your staging based on several factors. There are a couple of settings in the installer's menu that factor into this.

    These settings can be changed to adjust how many times the stat will attempt to cycle the system on and off every hour.

    However...

    Extended run time is actually kind of the point with a multi-stage system. A heat pump can take up to 10 minutes of running to reach "steady-state" operation, where everything has settled in and it is running at maximum efficiency. Stopping and re-starting all the time will reduce your efficiency as well as put additional strain on the system.

    Just like you don't turn off your car and re-start it at every red light. It's harder on the compressor to turn it on than it is to let it run.

    Longer run times while staging in and out will give you more even temperatures in the house and keep you closer to your set point rather than heating past it, then cooling down, and repeating...

    I'm curious, how long have you had this system and what did you have before it?

  3. #3
    Join Date
    Jan 2004
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    66,758
    The 8000 series is by temp only. Long run times is more efficient then short run times.

    However, the YTH9421 may be more to your liking. As it brings on second stage when it determines that the homes heat loss or gain is at 90% of first stage capacity.
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  4. #4
    Join Date
    Aug 2004
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    North Richland Hills, Texas
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    Honeywell calls it P+I control.


    Quote Originally Posted by beenthere View Post
    The 8000 series is by temp only. Long run times is more efficient then short run times.

    However, the YTH9421 may be more to your liking. As it brings on second stage when it determines that the homes heat loss or gain is at 90% of first stage capacity.
    Per the documentation for both thermostat series, the 8000 series and IAQ both use same P+I control setup.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Jan 2004
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    Haven't pushed the 8000 series lately. Last ones I used, needed a temp difference. Or I'm just getting more senile.
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  6. #6
    Join Date
    Dec 2010
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    8000 works on temp differance

  7. #7
    Quote Originally Posted by cjpwalker View Post
    There is a lot of math buried in that thermostat that controls your staging based on several factors. There are a couple of settings in the installer's menu that factor into this.

    These settings can be changed to adjust how many times the stat will attempt to cycle the system on and off every hour.

    However...

    Extended run time is actually kind of the point with a multi-stage system. A heat pump can take up to 10 minutes of running to reach "steady-state" operation, where everything has settled in and it is running at maximum efficiency. Stopping and re-starting all the time will reduce your efficiency as well as put additional strain on the system.

    Just like you don't turn off your car and re-start it at every red light. It's harder on the compressor to turn it on than it is to let it run.

    Longer run times while staging in and out will give you more even temperatures in the house and keep you closer to your set point rather than heating past it, then cooling down, and repeating...

    I'm curious, how long have you had this system and what did you have before it?


    I installed the system 6 years ago. It is a Climatemaster TT27 with a horizontal loop. It works great, but recently I've been wishing I had more control of the system than what the T-stat allows. I've been in commercial hvac for 15 yrs so I understand the efficiency part of it, but there are some other reasons I would like 2nd stage to come on a little sooner. This system was the original systems, but my last home had a duel fuel heatpump. I'm inrolled in some johnson control classes in the next few months so maybe I'll be able to program my own controller!? lol Over all I am happy with the 8000.

  8. #8
    Join Date
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    Well, a Cycles per Hour adjustment might be just the thing. Afraid I can't go into it any more than that here as the open forums are very limited on the kind of advice that can be given. If you are in the field you could qualify for professional status on this site.

  9. #9
    Join Date
    Oct 2012
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    Ohio
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    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 10-07-2012 at 12:33 PM. Reason: Non Pro * Member

  10. #10
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    dwikeson, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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