Under Floor Heating defaults to on after power cut

Discussion in 'Electricians' Talk' started by Stephen Bailey, Feb 11, 2018.

  1. Stephen Bailey

    Stephen Bailey New Member

    Electric under floor heating mats were laid in my kitchen two years ago and work fine but for one issue. When the thermostat is in the off mode and there is a power cut, the thermostat will turn on as soon as power is reinstated.

    The manufacturers felt it was a fault in the thermostat and provided a replacement but this does exactly the same as the original. So far no one has been able to determine why this is happening albeit they all agree that it should not default to on following a power cut.

    Has anyone experienced this issue before and if so do you have any suggestions. I am not an electrician but did build my own house so have some knowledge of electrical wiring but have never carried out any of the electrical work myself believing this to be something that I would rather leave to the experts but on this occasion even they appear baffled.
  2. unphased

    unphased Screwfix Select

    You need to speak to the manufacturers of the product. It can not be anything to do with wiring and, tbh, I think it is right that the thing should default to 'on' after a power cut. I think it should also do that if it was already 'on' before the power cut. If it defaulted to 'off' it would be far more of an inconvenience, imho. There must be a relay inside it.
  3. Bob Rathbone

    Bob Rathbone Well-Known Member

    Following a power cut the thermostat will sense the floor has got cold and the contacts will close when the supply resumes, assuming that sufficient time has elapsed.
  4. Stephen Bailey

    Stephen Bailey New Member

    Spoke with manufacturers a while ago and they say that it should not default to "on" if the mats were not on prior to power cut. The mats do revert to "on" if they were on prior to a power cut but they not do so if the mats were not on. I have exactly the same system and thermostat in another room and that does not power "on" after a power cut but does if the heating was on prior to the cut. That is the only reason I believe that something is not quite right with the kitchen installation albeit what I do not know. The only reason I am looking at it is that I was away for sometime a few weeks ago and there was obviously a power cut as the kitchen mats were "on" when I got back and had been for a few weeks but have to say that it was nice and warm!

    Thanks Bob and Unphased for your comments.
  5. Bazza-spark

    Bazza-spark Well-Known Member

    Stephen what is the make and model of the thermostat?

    Kind regards
  6. Stephen Bailey

    Stephen Bailey New Member

    The thermostat is a thermotouch touchscreen 4.3iC. 5240
  7. Bazza-spark

    Bazza-spark Well-Known Member

    Stephen, does the stat remain in On mode, or does it revert to Off after a period? It may be that because the sensor has been off it needs time to stabilize. What are parameter 5 and parameter 12 set to?

    Kind regards
  8. Stephen Bailey

    Stephen Bailey New Member

    The parameters are: 5 I & E and 12 5s

    The stat will remain "on" until the room teprature set is reached and then go to "off" before coming back on as the room cools. So it really picks up a normal mode of operation as soon as power is restored after a power cut even though it was not turned on prior to the power cut.

    Thank you for considering this matter it is appreciated.
  9. Bazza-spark

    Bazza-spark Well-Known Member

    Ok. So what do you have to do to get it to run your programms again?

    Kind regards
  10. Stephen Bailey

    Stephen Bailey New Member

    If it has turned on after a power cut I just turn it off because the power cuts occur outside of the programmed timings and then switch it back on after a period of time and it resumes the programmed timings as set.

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