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Thread: t-stat q's

  1. #1
    Join Date
    Jun 2006
    Posts
    8
    I am currious about a couple of things.
    What seems to be the normal "gap" setting for a t-stat to turn on, I know there is a simple word for this term but it eludes me at the moment. I have a entry level programable thermostat and it has a setting for how many degrees the temp is allowed to climb before the system turns back on, what is considered a normal or optimum setting for that.
    Also on a hot day in the summer what is considered a normal run/rest ratio for the a/c. I have what could be called zero humidity so the only priority I have is cooling. I know I aint gonna get optimum conditions from my a/c when the outside temp is 120+ but what about 105-115 should the unit be able to turn off for 1/3 or more of the day?

    Thanks in advance for any and all responces.

  2. #2
    Join Date
    Jun 2006
    Posts
    628
    Dead band maybe?

    AC should have protection to keep it from turning back on for about 5 minutes, but I think that is the only restriction.

    System should run continuously on the hottest days of the year and keep the indoor setpoint, off 1/3 of time sounds oversized, but for us desert types so what.

    A "smart" thermostat looks at run times and uses a predictive calculation for maximum comfort, since cool air blowing, FEELS a lot cooler than same room temp and no movement. Things like running the fan at intervals even without the cooling.

    Are you "looking" for a problem, or is something bothering you?

  3. #3
    Join Date
    Feb 2006
    Posts
    168
    natedude,

    I think the term is "swing temp adjustment". On my thermostat the swing can be adjusted in quarter degree increments up to 2.25 degrees. Like you, I don't have significant dehumidification concerns such that I need long run times to take the moisture out. I use the swing to make sure I have sufficient run times so the equipment is not starting and stopping so many times over the day. I try to have twenty to thirty minute runs, but that's pretty easy in the heat of the summer. I think my present swing is 1.25 degrees. In our kind of heat, I like to have my system cycle, and get some rest, so to speak. My system is oversized due to reduction of load from home improvements, but without dehumidification needs and our heat, I really don't mind because it does allow the system to cycle. Indoor humidity usually runs between 35-45%.

  4. #4
    Join Date
    Jun 2006
    Posts
    8
    Originally posted by danglerb
    Dead band maybe?


    Are you "looking" for a problem, or is something bothering you?
    This is the result of someone at work telling my wife that the proper sized a/c should only run part of the time. During the spring and fall mine will run part of the time, but when the mercury boils out of the glass my "little" unit stays on from a little after sunup to a little after sundown, when all is well the temp doesn't get to far away from what it's set at, it just won't go all the way down. So I am not looking for problems, I am looking for ammo against my problems.
    Thankyou.

  5. #5
    Join Date
    Apr 2005
    Location
    Kingston Ontario Canada
    Posts
    1,213
    Originally posted by natedude
    Originally posted by danglerb
    Dead band maybe?


    Are you "looking" for a problem, or is something bothering you?
    This is the result of someone at work telling my wife that the proper sized a/c should only run part of the time. During the spring and fall mine will run part of the time, but when the mercury boils out of the glass my "little" unit stays on from a little after sunup to a little after sundown, when all is well the temp doesn't get to far away from what it's set at, it just won't go all the way down. So I am not looking for problems, I am looking for ammo against my problems.
    Thankyou.
    Natedude: Sounds like your system is just about properly sized. AC should run just about all the time in the very hottest weather. You could say any system is oversized when the outdoor temperature is lower then what the system was designed for. That's why size is critical, because the very hottest days are the only ones where you need maximum AC and the rest of the days when it's cooler then design temps your AC will cycle on and off. It's on these cooler days if your system is oversized it will not run long enough to dehumidify, and that's the # 1 job in AC...DEHUMIDIFICATION.

    Thorton
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