Need guru's advice on Single zone Thermostat 5070THBRPG

Discussion in 'C-Bus Wired Hardware' started by greefon, Apr 6, 2012.

  1. greefon

    greefon

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    Hi everyone!

    5070THBRPG thermostat's behavior seems to me a bit strange - can someone tell if it's normal or not, please?
    Example: when the user adjusts the set point to 25C and the temperature is 22C - thermostat activates heat and fan (relays click inside thermostat). In 10-15 minutes thermostat deactivates the relays (temperature is something like 22,5C) and wait for 2-5 minutes (sun icon flashes on LCD) than again turns on heat and fan and so on in loop mode.
    How to make the thermostat to send heat without turning off until the temperature is 25C ??

    Another question: Setback. When it's active, thermostat, like it's said in manual, turns on (in heat mode) when the temperature is above the setpoint "minus" setback. Example - Setback is 2. Temperature is 21.9C, Setpoit - 25C. Nothing happens... Only when I increased to 26C - it turned on... 26C minus 21.9C is 4,1C - it doesn't look like setback value = 2.
    Heat mode worked for 3-4 minutes and relays inside clicked off (temperature is 22.2C, fan and sun running like heating mode is on).
    Please someone how knows the thing - explain me: is it normal working condition for Setback?
     
    Last edited by a moderator: Apr 6, 2012
    greefon, Apr 6, 2012
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  2. greefon

    tobex

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    Thermostats have the disadvantage of usually sitting on a wall where convection currents affect the readings. Have you taken a temp of the air around the thermostat.
     
    tobex, Apr 7, 2012
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  3. greefon

    ashleigh Moderator

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    tobex makes a good point.

    The location of the thermostat is important, you do not want it to be where there is poor air circulation. Mounting it on external walls (which can be hotter or cooler than the inside of a building) is also not a good idea. The temperature sensor IS mounted away from the wall surface, but the air in external walls can be cooler or hotter than elsewhere.

    Also, if the thermostat is mounted where it is in the path of an air outlet there will be an air draft on it, this can mean it has localised heating (or cooling) and this will have it responding too soon.

    Re setpoint: the thermostat has a normal hyseresis, I think from what I can remember that this is +/- 0.5 degrees C. So if you set 25 degrees as your setpoint, it will try and regulate the temperature in the range 24.5 .. 25.5 degrees.

    When you activate setback, the allowable range is widened, in your example of setback of 2 degrees C, then a setpoint of 25 degrees should see an attempt to regulate inside the range 22.5 .. 27.5 degrees C. [There may be an additional 0.5 degrees applied, I can't remember, but if so this would make 22 .. 28.]

    The most likely reason why you see slightly different numbers is the location of your temperature measuring probe is different to the location inside the thermostat.

    ----

    A possible reason for the relays clicking in and out could be the plant type you have set. You did not say what plant type you have configured. Some plant types have an assumption of a slow response time which the thermostat will try and model - so it will heat for a while, then turn heating off expecting that the air temperature will continue to increase. This is *maybe*. It depends on how things have been set up.
     
    ashleigh, Apr 7, 2012
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  4. greefon

    greefon

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    Thanks for your replies!

    Two thermostats are on the walls: one is in the big studio room on the first floor, second in the corridor on the second floor. I used simple thermometers to check if the readings of thermostats are right - no difference between thermostats and thermometers I've found.
    I also set Temp offset (-1 - 1,5 deg) because the temp in the rooms are slightly lower than near thermostats themselves.
    HVAC system is Nordyne (Intertherm) furnace with AC outdoor. Also have Honeywell zone controller HZ311 TrueZONE for keeping up all together - thermostats, dumpers, furnace. But they just receive signals from thermostats and executes them.
    For all the types of Operations in C-Bus Toolkit (heat, cool, vent, heat/cool) I have set "Furnace / Heat pump - cooling only". Is this fine for my type of system?

    Again about Setback: Still can not get why it works so - Setback is 2, Setpoint 25, temp - 22. Thermostat asked for heat for several minutes and turned off. Temp is fallen to 21.1C. I thought that in setback mode thermostat must heat until the setpoint is reached? Setback just makes bigger derivation in setpoint. So why it stops after the first switching on and not keep heating?
     
    Last edited by a moderator: Apr 7, 2012
    greefon, Apr 7, 2012
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  5. greefon

    ashleigh Moderator

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    The plant type Furnace / Heat Pump - cooling only should be ok.

    I don't know why it is doing this.

    There is a toolkit option you can set (and I do not remember what it is called but I think it is in the last tab, or maybe 2nd to last) which is used to communicate between several thermostats.

    If you ENABLE this option, then use the c-bus diagnostic s/w you should see regular messages from the thermostat where it is transmitting messages saying what it thinks is happening (these contain the current plant demand, set point, and a lot of other information).

    Using this you may learn a bit more about what the thermostat thinks is happening.
     
    ashleigh, Apr 7, 2012
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