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  1. #1
    Join Date
    Jul 2014
    Posts
    108
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    cycling 2 units to work together at different time

    hello everybody

    I got a project where requirements are, 2 units for the same room, unit A work at the first call for cooling, then thermostat get satisfied and unit A turn-off, when thermostat call again for cool, unit B must turn ON and the work cycle star over.

    how can I control that and is the name of that arrangement an arrhythmic cycle?

  2. #2
    Join Date
    Dec 2006
    Location
    Vancouver, B.C.
    Posts
    361
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    We’ve always used DDC to control systems like that.




    Sent from my iPhone using Tapatalk
    Quickly, I must hurry, for there go my people and I am their leader!

  3. #3
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    8,069
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    Search out a control that is called a lead - lag which will give you that opportunity.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  4. #4
    Join Date
    Jul 2014
    Posts
    108
    Post Likes
    Thread Starter
    everybody tanks, it is really helpful

  5. #5
    Join Date
    Mar 2008
    Location
    kansas
    Posts
    1,245
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    Search alternating relay it can be simple and cheap ,or get pretty exotic. Add another t stat and you have a high temp option in case of failure
    Honeywell you can buy better but you cant pay more

    I told my wife when i die to sell my fishing stuff for what its worth not what i told her i paid for it

  6. #6
    Join Date
    Mar 2008
    Location
    Mesa, Az
    Posts
    107
    Post Likes
    Bard makes a lead lag controller. Pretty simple to install and reliable operation. I think model MC4002

  7. #7
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    739
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    I believe Honeywell T775 has lead lag abilities.

    Sent from my SM-G960U using Tapatalk

  8. #8
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    739
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    It does and it has runtime options

    Sent from my SM-G960U using Tapatalk

  9. #9
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    21,458
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    Manually alternate once a year.

  10. #10
    Join Date
    May 2018
    Location
    VA/DC
    Posts
    112
    Post Likes
    if you email me tomorrow I'll put the one off my shelf and give you the name. I just cant think of it right now.
    its simple and effective for what you want

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    39,769
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  12. #12
    Join Date
    Sep 2002
    Posts
    24,828
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    A lead/lag latching relay circuit would do it non-electronically but I can't believe that there isn't some kind of lead/lag switching control available off-the-shelf.

    PHM
    --------


    Quote Originally Posted by Takete View Post
    hello everybody

    I got a project where requirements are, 2 units for the same room, unit A work at the first call for cooling, then thermostat get satisfied and unit A turn-off, when thermostat call again for cool, unit B must turn ON and the work cycle star over.

    how can I control that and is the name of that arrangement an arrhythmic cycle?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  13. #13
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    21,458
    Post Likes
    Quote Originally Posted by Poodle Head Mikey View Post
    A lead/lag latching relay circuit would do it non-electronically but I can't believe that there isn't some kind of lead/lag switching control available off-the-shelf.

    PHM
    --------
    Heatcraft makes them. Pricy.

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