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Devimat confusion

Discussion in 'Electrics UK' started by raine, 1 Nov 2018.

  1. raine

    raine

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    Hi,

    I've just moved into a flat with Devimat heating and am confused about the settings / display.

    1. Should the mat switch off as soon as it reaches the end of the "on" time?
    This morning, I noticed that the Devireg 550 controller in one of the rooms was showing the heating-up symbol about 40 mins after the end of my configured heat-up time. I fully understand that it will come on before the "on" time, but after?? It was very warm in the room, and it was a full 10 hours until the next heat-up time. The set-back "LO" temp is set to -12, and the sensor is set to rFS.

    2. Is there any way to display the current room temp on the display?

    3. When on timed but outside of the configured heat-up times, what is shown on the display? Is it still the target temp for the heat-up times, or is it the "LO" temp? If the former, is there any way to show the set-back temp?

    4. How accurate are the thermostats? I seem to have to set wildly different temps in different rooms to achieve what feels like the same temperature.
     
    Last edited: 1 Nov 2018
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  3. ericmark

    ericmark

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    The instructions say
    In general under floor heating is split into two types, chemical where the heating mat is to some extent self regulating and simple heating element, neither are really good enough to heat the house on their own, I have it in a wet room to dry the floor, without the towel rail the room is rather cold, I think UK the limit is 27°C so if wanting 20°C there is only a 7°C differential which really is not enough, however with a heat recovery unit and very good insulation it can keep the home warm, but needs to run nearly 24/7.

    The thermostat is designed to try to make a silk purse from a sows ear, even with water filled radiators I have in my house the time delay heating and cooling is rather long, in the main because software tries to stop it over shooting, so with setting at 20°C and room at 16°C first 2°C quite quick but next 2°C much slower, and although set over night to drop to 12°C it never cools that much, 16°C is about limit to what the room will drop to. The floor stores more heat to water filled radiators so likely the temperature will only drop or rise 2°C through the 24 hours.

    However other end of scale is the fan assisted radiator, very fast to heat a room, but also fast to cool, new type with automatic 4 speed on modulating boiler are I am told a lot better, but it is a balance, comfort to cost.
     
  4. raykf

    raykf

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    "rFS" looks as though the stat may be set to control the floor temperature (FS - floor sensor) and not the room temperature.
     
  5. raine

    raine

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    Thanks for the responses so far.

    This is not a new installation, so I wouldn't expect that it would need to learn the heating characteristics of the room, I think? It was powered off when I moved in though, and I have changed the timer settings - would it need to re-learn after this?

    I will monitor for a couple of days and see if it changes.

    Not quite. According to the manual:
    rFS = Room & Floor Sensors
    rS = Room Sensor
    FS = Floor Sensor

    Maybe I should try rS?

    Further update since my post:
    Yesterday evening, I didn't see the heat-up logo appear at all during the timed period (I was out before the period so couldn't check). Immediately after the end of the period, the heat-up logo came on (9 hours ahead of the next timed heat period). It's almost as though it's got confused and is working directly opposite to what it should do - is that possible??

    Any response on my other questions please?

    2. Is there any way to display the current room temp on the display?

    3. When on timed but outside of the configured heat-up times, what is shown on the display? Is it still the target temp for the heat-up times, or is it the "LO" temp? If the former, is there any way to show the set-back temp?

    4. How accurate are the thermostats? I seem to have to set wildly different temps in different rooms to achieve what feels like the same temperature. (in one room, I have to set the target temp to 34 degrees before it will come on)
     
  6. ericmark

    ericmark

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    As said these systems do have to learn, my UFH is very basic, and not impressed, clearly not new as obsolete, however personally I would not spend out as never very good. I can only read instructions same as you and already given you the link.
     
  7. raine

    raine

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    Update on this thread:

    Of course, it was nothing to do with the system needing to learn anything.

    Turns out the controllers are U/S. I rang the Danfoss helpline and they explained that the Devireg 550 is a very old controller, which tends to develop various "gremlins" until it eventually gives up completely. In this instance, it's basically keeping the room warm 24x7 and ignoring the timer. The only way to resolve is replacement.

    Now all I have to do is persuade the landlord to replace the controllers.

    On my other questions:
    The Danfoss helpdesk told me:
    There are essentially two modes for the controller - TIMED and MANUAL. When in TIMED mode, the screen always displays the target temp for when it's ON, even during OFF periods. When in MANUAL mode, again, it displays the target temp.
    There is no way to display the current room temp or the set-back temp.
     
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