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  1. #1
    Join Date
    Jul 2012
    Location
    Phoenix, AZ
    Posts
    40

    Three stage cooling and Two stage heating.

    I helped install a new residential multistage heat pump system that was equipped to provide three stages cooling with two stages of heating. To be honest I really dont understand how all the stages of heating and cooling were to be accomplished by the t-stat. I guess its something that I never picked up, or really understood but what I don't understand clearly is how or what controls the stages? Any takers?

  2. #2
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    3 stages? How was that managed?

    You might need one of those little PLC type programmable controllers with display that has analog inputs and at least 6 digital outputs.

  3. #3
    Join Date
    Jan 2002
    Location
    Fayetteville, NC
    Posts
    133
    A digital t-stat with 5 relays could easly do it. Pretty easy really. Honeywell make 3H/3C t-stats. Not cheap thou.

    http://customer.honeywell.com/honeywell/productinfo.aspx/T7350H1009

    Sent from my DROIDX using Tapatalk 2
    Supermarket Tech...and anything else the boss finds for me!

  4. #4
    Join Date
    Dec 2007
    Posts
    4,764
    I do not understand how there would NOT be more stages of heat.

    You should have the same heat and cool from heat pump(in theory) as well as at least 1 stage of back up, maybe more.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  5. #5
    Join Date
    Jan 2002
    Location
    Fayetteville, NC
    Posts
    133
    Mind you this is a guess, 3 compressors and 2 reversing valves.

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    Supermarket Tech...and anything else the boss finds for me!

  6. #6
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    What brand?
    If more government is the answer, then it's a really stupid question.

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by mark beiser View Post
    What brand?
    I'm really curious on this. I'm having trouble seeing the value over something like a Carrier Greenspeed.

    Maybe it's a two scroll unit with two refrigerant circuits and one of the scrolls unloads? But in heat, you only run with both loaded, since I think unloaded you don't gain any efficency in heating mode.

    Or a custom air handler with a A coil that has 2 refrigerant circuits and one of them is a 2 stage condenser.

    An interesting alternative when you think about it in applications where you want some redundancy and a sytem that rusn almost constantly or has a very small zone, but don't need more than 5 tons and are space limited to a single air handler. but it seems to me that an inverter unit would be better.

  8. #8
    Join Date
    Jul 2012
    Location
    Phoenix, AZ
    Posts
    40
    Your right looking at it agian its 3heat and 3 cooling.

  9. #9
    Join Date
    Jul 2012
    Location
    Phoenix, AZ
    Posts
    40
    Trane.Trane.

  10. #10
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,505
    Are you absolutely sure it isn't the much more common 2 cool/3 heat?

  11. #11
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,429
    maybe controlling two units off one tstat? a/c units and furnaces?

    I had a 3 cool, 2 heat a few yrs back. used a time delay for last stage.
    Col 3:23


    questions asked, answers received, ignorance abated

  12. #12
    Join Date
    Jun 2010
    Location
    Nelson, Canada
    Posts
    12

    3H/2C

    This is quite common on geo systems and I would think on most air source HP's.
    Generally you would have a two stage compressor with two stages of heat and two of cool & 1 back up. I'm pretty sure most t-stats i've used have a time delay or a combination of temperature change over time for the back up/3rd stage relay.

  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by zacmobile View Post
    This is quite common on geo systems and I would think on most air source HP's.
    Generally you would have a two stage compressor with two stages of heat and two of cool & 1 back up. I'm pretty sure most t-stats i've used have a time delay or a combination of temperature change over time for the back up/3rd stage relay.

    But he's talking about 3 cool, 2 heat. The vision pro IAQ will do 4heat, 2 cool. But I haven't seen one that will do 3 cool, there's not much demand for it.

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