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Thread: Help with my Chiller and Heater program

  1. #1
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    Help with my Chiller and Heater program

    I just added a chiller to my system almost a week ago and was using this programming to keep my temps between 76-78F, which worked well:

    [Chiller]
    Fallback OFF
    If Temp > 78.0 Then ON
    If Temp < 77.0 Then OFF
    If Output ReturnPump = OFF Then OFF
    Defer 001:00 Then ON

    [Heater]
    Fallback OFF
    If Temp < 76.0 Then ON
    If Temp > 77.0 Then OFF
    If Temp < 70.0 Then OFF
    Defer 001:00 Then ON

    [ChillerPump]
    Fallback ON
    OSC 000:00/001:00/239:00 Then ON
    If Output Chiller = ON Then ON
    Defer 001:00 Then OFF

    With the program above I noticed my chiller running on and off every hour (one hour on, one hour off, etc). Today I found out my chiller manufacturer recommends a minimum of 2-3 degree variance to reduce cycling on and off. I've updated the program as follows and wondering if this suffice or will it conflict with my heater program:

    [Chiller]
    Fallback OFF
    If Temp > 78.0 Then ON
    If Temp < 76.0 Then OFF
    If Output ReturnPump = OFF Then OFF
    Defer 001:00 Then ON

    [Heater]
    Fallback OFF
    If Temp < 76.0 Then ON
    If Temp > 77.0 Then OFF
    If Temp < 70.0 Then OFF
    Defer 001:00 Then ON

    [ChillerPump]
    Fallback ON
    OSC 000:00/001:00/239:00 Then ON
    If Output Chiller = ON Then ON
    Defer 001:00 Then OFF

    Any help will be greatly appreciated.

  2. #2
    Frequent Contributor zombie's Avatar
    Join Date
    Dec 2013
    Location
    Denver, CO
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    13,176
    That will most likely conflict with your heater as there is some latent cooling that will occur even after it turns off. I would personally increase the low threshold up at least a half a degree.

    You might be an engineer if...You have no life and can prove it mathematically.

  3. #3
    Frequent Visitor rkpetersen's Avatar
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    Quote Originally Posted by neeper View Post
    If Temp < 70.0 Then OFF
    Is this line to guard against a failed temp probe reading low and causing the heater to run away and cook everything?

    Would this generally be used with heaters that don't have an internal thermostat?

  4. #4
    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by rkpetersen View Post
    Is this line to guard against a failed temp probe reading low and causing the heater to run away and cook everything?

    Would this generally be used with heaters that don't have an internal thermostat?
    Yes. If using only one heater with a internal thermostat it should not be used. If using 2 or more heaters its best to use that on just one so that the temp doesnt quickly spike if it wigs out. If using one without a thermostat that line is essential.

    You might be an engineer if...You have no life and can prove it mathematically.

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