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Unruly thermostat

Discussion in 'Plumbing and Central Heating' started by hi1, 8 Nov 2018.

  1. hi1

    hi1

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    System is a stellis GVSC 28-2 H condensing boiler on lpg with a Honeywell CM 907 controller - thermostat.
    The problem is that despite my best efforts the controller seems to ignore totally the times programmed into it and operates solely on the command of the thermostat function. The controller is situated in the kitchen where theres a small woodburner which is lit most days. This seems to keep the room at a temperature of or above that set in the controller. When the temperature falls below this the boiler is fired up regardless of time of day or whether its supposed to be on. Instructions I have are in French for boiler but have English for thermostat which in all honesty seems over engineered for what its asked to do. Any suggestions please, all gratefully received
     
  2. ericmark

    ericmark

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    I had a problem with my programmer/thermostat seems I had set Monday to Friday, but missed setting Saturday and Sunday which were programmed separately.

    I wonder if there is a frost stat some where which is switching boiler on, and not the main thermostat, so turn it fully off and see it boiler still firs up.
     
  3. hi1

    hi1

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    Thanks for your reply IMG_20181113_102736.jpg IMG_20181113_102744.jpg IMG_20181113_102759.jpg
     

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  4. hi1

    hi1

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    and in boiler IMG_20181113_104115.jpg


    Looking at the pictures I've a few idiot questions
    On the sticky label on the thermostat back on wall its shows C3, is this the function being carried out by the controller to make a circuit, either time for boiler to be on and or temperature selected.
    The cable colours are from the controller to the boiler are they the right way round, does it make a difference?
    On the controller pcb theres a black line leading off from one of the terminals does that indicate burnt out or never had the copper bit on the pcb in the first place. If burnt out could that be the result of the wiring being incorrect
    thanks
     
  5. SFK

    SFK

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    Hi1,
    1) I always see the Sticker in the thermostat as showing the circuit when when the thermostat/Timer is OFF (ie at correct temp)
    So A and B are not connected when thermostat/Timer is OFF and A and B are joined together when their is a call for heat
    So that looks correct.

    2) I do not know if you have correct polarity in the Brown and Orange cable, but I feel that it should not matter in your case as this thermostat/Timer uses batteries to power it this is acting as a simple switch.
    But if you are capable, you could test with a Multimeter.

    3) The black track coming from T3 is strange, but I think that is simply going to a test pad so not important.

    4) And here is a good programming manual


    My Thoughts
    A) If it is switching on and off the boiler as per its internal thermostat, but not the timer, then I feel that it is either:
    - Stuck/Broken in the "Manual" mode or
    - You have programmed the timing frequency with temp wrong (a lot of people seem to do this with the multiple entry points, especially with the last one.

    Testing and questions:
    1) Does the Flame signal come on when the boiler comes on, and teh flame signal go off when the boiler is off?

    2) As Eric said, "so turn it fully off and see it boiler still fires up"

    3) When the thermostat/Timer is not on the wall (as in your photo) there is no connection between the wires so Boiler should be off. Is it off?

    SFK
     
  6. hi1

    hi1

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    Thanks for your time to reply
    In answer to your points
    1 the boiler comes on when the flame symbol is shown on the controller. The flame only shows when the ambient temperature of the kitchen falls below that set on the controller and the boiler then fires. It doesn't matter whether that's within a programmed time period. So really its a reverse of your question
    2 the only way to stop it firing up is to select off position which also gives a 5 degree frost protection whether it fires up then I don't know because we have not so far been that cold. It fires up on both manual and auto positions selected only stopping when ambient temperature is reached. By reducing or increasing the ambient temperature the boiler firing up can be controlled
    3. Without command from controller boiler doesn't fire even when temp selection for heating is turned to max
    I do not understand the temp wrong with the programming frequency. It has six time options. I have first two for morning, cancelled the middle two, 3 and 4 and set 5 and 6 for the evening operation. temperature constant for all times and days
    regards
     
  7. flameport

    flameport

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    It's working as intended.
    If you set the same temperature all the time, it will turn the boiler on/off to maintain that temperature all the time, whether it is morning, noon, night or anything else.

    This is not a device where you say 'heating on at 8am and off at 11am'.
    It's a device where you say 'at 8 am I want the temperature to be 20C', 'at 11am I want it to be 12C' and so on.

    For periods where you are not in the building or want a lower temperature (such as at night), you set the temperature for that time to be lower.
     
  8. ianmcd

    ianmcd

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    as @flameport says that is how it works and just to add if you are at a period where the thermostat is set in a lower position and you manually turn the thermostat up it will be set at whatever temp you set it to until the next timed period, you just need to learn how to operate and programme it , it is installed and operating correctly
     
  9. SFK

    SFK

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    Hi1,
    As the others have said, it looks as if your Programmer is working correctly and you are in the "You have programmed the timing frequency with temp wrong (a lot of people seem to do this with the multiple entry points, especially with the last one)".

    I have had this issue several times with people not understanding this type of programmer.

    The way I "try" and explain it is:
    - The day is broken up into 6 segments
    - These segments have a start Start time (which the time you enter for that TimeSegment), and the End Time (which is the time you enter for the NEXT TimeSegment).
    - You define the temperature you want in each time segment.
    - If you want the boiler off, put the temperature in that time segment to be very low (say 5oC for frost protection, or say 14ºC so house does not get too cold in a very frosty period).
    - So as an example, if you programme the following into your Programmer:
    > Segment #1: 06:00......22ºC
    > Segment #2: 08:00......10ºC
    > Segment #3: 12:00......10ºC
    > Segment #4: 16:00......22ºC
    > Segment #5: 18:00......22ºC
    > Segment #6: 23:00......8ºC
    > (do not have "temperature constant for all times and days" and do not "Cancel" any - as I do not know what this does).

    then the above programming means that:
    > Between 6am and 8am the boiler will try and warm house to 22ºC (likely that boiler/flame is ON)
    > Between 8am and 12noon the boiler will try and warm house to 10ºC (likely that boiler/flame is OFF)
    > Between 12noon and 4pm the boiler will try and warm house to 10ºC (likely that boiler/flame is OFF)
    > Between 6pm and 11pm the boiler will try and warm house to 22ºC (likely that boiler/flame is ON)
    > Between 11 and 6am (overnight) the boiler will try and warm house to 8ºC (likely that boiler/flame is OFF)
    And then cycle starts again...
    > Between 6am and 8am the boiler will try and warm house to 22ºC (likely that boiler/flame is ON)
    > etc


    As you can see from my example I have target temp a bit warmer during the day and colder at night.
    Hope this helps, SFK
     
    Last edited: 22 Nov 2018
  10. hi1

    hi1

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    Thanks for all your time in making your replies. I understand the principal now but to be honest I'd just as soon go back to using the dial with segments like I had on my Worcester 24i.
     
  11. SFK

    SFK

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    Hi1,
    "I'd just as soon go back to using the dial with segments" - yes, fully appreciate that - similar to comments that I hear from others regarding timers with the 6 programmes.
    SFK
     
  12. flameport

    flameport

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    Cancelled ones are just removed, and effectively extends the previous setting, with the examples listed if #4 was cancelled, the previous 10C would apply until 1800.
     
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