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Thread: Newbie Evohome (Miss)Understanding

  1. #1
    Automated Home Ninja Mavis's Avatar
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    Default Newbie Evohome (Miss)Understanding

    Some more help needed please as I can’t get to grasps with it my Evohome! I think I understand the concept of it as I had a programmable thermostat in my previous home and I know that the system is not off or on. (BTW, I like to think that I am a bit of a techie so want to get to grips with this)

    I have checked and all radiators work by:-
    a. Manual override
    b. Control panel

    All room doors closed.

    Firstly – am I right in thinking that if you use the manual override on the HR92 then this takes precedence over the programming (ie even if you pass a setpoint in the programme times the temperature will not change until you turn the HR92 back.)

    My system appears to have a mind of its own as the temperatures on the controller do not match the room temperature. I have stood a thermometer next to where the HR92 is and there can be a difference of at least 3 degrees, for instance air temp is 16 degrees (and feels 16 degrees) but the controller is reading 18.5C so the radiator is therefore not kicking in.

    For instance, this morning (all radiators are set at 10C during the night) The bathroom and hall were set to 19C at 6am. Heard the hall valve turn at about 5.50am so all good. (Both bathroom and hall radiators were hot at 6am) BUT the kitchen radiator was also on. I checked the HR92 display and checked the controller and neither had been overridden.

    Last night –
    kitchen reading 21.5C on the controller,
    sitting room reading 18.5 on controller (smallish room with door shut and large flat screen TV on so room felt at least 22C )
    hall reading 19C but more like 16C

    Can someone guide me through how to check that everything as it should be.

    I suppose my goal is how can I get each room to be at an optimum temperature at least in the evening to stop my husband moaning that it is too cold!

  2. #2
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    How are your TRV's fitted to the radiators ? Did you need to fit adaptors to the valves, or just screw them on ?

  3. #3
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    Hi Mavis,

    Like you, we are also trying to get to grips with our Evohome system. The lack of user information is Evohome's Achilles Heel.

    If you manually adjust a TRV or a zone target temperature, it should remain at the new temperature until the next programmed switching point.

    The problem with your kitchen radiator is most likely due to the TRV head not closing off the valve properly. If you think about it, the pin that extrudes from the TRV body has to be fully extended to close the valve. I am not an installer but I can think of 3 reasons why this might be the case.

    1. The new rad head has not been fitted properly and it is applying constant pressure to the pin.

    2. The pin is sticking in the open position.

    3. The pin is slightly too long. (there is something about this in one of the HW bits of paper).

    What would I do? I would find the installation guide for HR92 and remove the head from the radiator. I would look for something like a piece of wood and use it to 'exercise' the pin in the valve. I would then replace the head according to the guide - noting that you have to wind it a particular way before installation - and then check the valve operates normally. Alternatively, you could just give your installer a call.

    Temperature differences. The HR92 guide states the following:

    Parameter 7 – Temperature representation in the
    display
    • In the factory setting the room setpoint temperature
    is displayed.
    • With the setting "measured temperature" the
    measured room temperature is displayed. A
    changeover to the set temperature is carried out by
    turning the adjustment dial or pressing the button.
    If required, the temperature can now be reset. The
    display returns to the measured temperature after
    approx. 3 seconds.
    Due to the heat influence of the radiator the
    "measured temperature" displayed at the radiator
    controller can differ from the temperature measured
    at another point in the room.

    Parameter 8 – Temperature offset
    Since the radiator controller measures the room
    temperature in the area of the radiator, it is possible
    that this temperature deviates from the temperature
    measured at a different point in the room.
    If, for example, 20 °C is measured in the room and
    21.0 °C at the radiator, this effect can be compensated
    by an offset of –1.0 °C.

    Parameter 10 – Display of the valve position
    When this parameter is activated (setting "1"), the
    calculated valve position (0 ... 100% opened) is
    displayed momentarily.
    The main display is shown again after approx. 3 minutes.
    To cancel, select exit and press the button.
    Parameter 11 – Window open function
    • If a window contact is connected, the parameter is set
    automatically to "2" (cabled). The window function is
    controlled by the window contact.
    • If no window contact is connected, the setting "0" or
    "1" has to be selected.

    I think that there has to be a bit of trial and further trial here. HW does offer remote room sensors (at cost) which I assume would eliminate much of the problem. Alternatively, you can tweak the parameters in the valve head or do, as I suspect most people do, which is to add a couple of degrees to the target temperature in the controller.

    Hopefully, as more people use the system the level of collective knowledge will grow.

  4. #4
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    Quote Originally Posted by Mavis View Post
    Firstly – am I right in thinking that if you use the manual override on the HR92 then this takes precedence over the programming (ie even if you pass a setpoint in the programme times the temperature will not change until you turn the HR92 back.)
    Yes, if you manually set a temperature on the rad controller, this overrides everything. Also, the temperature you've set on the rad controller will NOT show as the target temperature on your main evohome controller, which I know is a little confusing.

    Quote Originally Posted by Mavis View Post
    My system appears to have a mind of its own as the temperatures on the controller do not match the room temperature. I have stood a thermometer next to where the HR92 is and there can be a difference of at least 3 degrees, for instance air temp is 16 degrees (and feels 16 degrees) but the controller is reading 18.5C so the radiator is therefore not kicking in.
    The temperature displayed on the rad controller is the current target (setpoint) temperature, by default. You can change this in the settings on the rad controller so it shows the actual room temperature, rather then the target temperature. If you find your rad controller's actual temperature reading is quite far out from what you expect, you can also change the temperature offset within the settings on the rad controller so it more accurately matches the actual room temperature.

    I hope this helps?

    Matt

  5. #5

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    The HR92/HR80 units have two modes of operation, a low power mode for when they are fitted to Honeywell valve bodies (which need less force to close) and a full power mode for non-Honeywell valves. So changing the mode may help if the Kitchen has a non-Honey TRV.

    You should also check the valve does close manually (using either the old TRV head or manually closing the HR92 dial which you can access with the top part of the actuator removed). If the valve is sticking or not properly sealing then the valve body needs replacing.

  6. #6
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    Quote Originally Posted by SensibleHeatUK View Post
    The HR92/HR80 units have two modes of operation, a low power mode for when they are fitted to Honeywell valve bodies (which need less force to close) and a full power mode for non-Honeywell valves. So changing the mode may help if the Kitchen has a non-Honey TRV.
    .
    I must be missing something here. The HR92 installation guide states:

    Parameter 6 – Valve stroke
    The radiator controller operates with the optimum valve
    stroke set in the factory.
    If the entire valve stroke is to be used or if the valve does
    not open completely, activate the full-stroke mode.

    Is this not the opposite of the OP's problem - or have I got my pin positions the wrong way round? That is, pin extended = valve closed: pin compressed = valve open.

    Or, are you talking about something different? If so, how are the two modes of operation set/changed on the HR92? Thanks
    Last edited by HenGus; 25th October 2014 at 06:17 PM.

  7. #7

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    This is the mode that should be adjusted (on the HR80 it was call default and full), and it relates to how far down the actuator presses to close the valve. So if the existing TRV is old (with a hardened plug) or a non-Honeywell model, it may need this mode set to fully close. Bear in mind that valve may not be linear in operation meaning even at just a few percent of valve stem travel from the closed position you may get a large amount of flow. So in this case it is worth trying this mode to see if it helps, if it does not then it seems likely the valve body needs swapping for a new replacement.
    Sensible Heat
    SensibleHeat.co.uk

  8. #8
    Automated Home Ninja Mavis's Avatar
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    Thanks for these replies - we have been away over the weekend so I will digest and try/reply later.

    BTW we got someone local in to install the system picked from the Honeywell 'Find an Installer' page. I got the impression though that this was probably the first install that he had done.

  9. #9
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    The reason I asked about whether you were using adapters or not, was that when I fitted my system originally, I used the adaptors and I had not seated them down all the way. This meant that the HR80 was not properly closing the valves. I mucked about with sticky valves, actuator default or full values etc. Nothing worked. Until, I realised that the adapters were not fully fitted in place. I fixed them and it all worked perfectly after that.

  10. #10
    Automated Home Ninja Mavis's Avatar
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    I am not sure if we have adapters on as we didn't fit the system. But there was a bag of adapters left after they were fitted.

    I have had a play around and changed some of the settings such as the temperature displayed and will keep an eye.

    If I had a faulty valve (or pin or TRV) would the radiator always be on (or always be off) if the system was running to heat any other radiator.

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