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Devireg 550 no display

Discussion in 'Electrics UK' started by malice67, 25 Oct 2015.

  1. malice67

    malice67

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    The thermostat is not doing anything. No 'CODE' or 'OFF' or anything being displayed, despite twisting, pressing and turning numerous times... Any ideas? The manual offers no help whatsoever…
    Cheers!
     
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  3. eveares

    eveares

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    The thermostat has got a very simple wiring plan, with just a Live and Neutral supply from the mains and a Live and Neutral load to the heating element, Plus two terminals for the temperature sensor and a further two terminals for linking several units together also doubling up for advanced USB control.

    First check that there is no switched/un-switched fused spur/s that may be isolating power from it as it will likely have. One you are sure that the unit has power to it, check that it has been wired properly. For important safe mains isolation procedures and general saftey see here.

    See the picture below for how it should be wired:



    Edit:

    Also, if it is being used with underfloor heating, ensure the earthed braid of the heating wire is connected to the earth.

    At the same time and if your using the thermostat for electric UFH, It is also wise (if possible) to:

    1) Do a 500V DC Insulation Resistance test between the heating elements earthed braid and the line and neutral conductors of the cold tail. You should get a reading >20MΩ's. Also check the instillation instructions of the UFH to be sure of the minimum acceptable value during this test as it may be higher than 20MΩ's.

    2) Do a resistance test between the line and neutral conductors of the cold tail and check that the reading is within that specified in the instillation instructions for the length of cable that you have installed.


    These two test above what must be done with the underfloor heating wire disconnected from the thermostat!, will ensure that your underfloor heating cable has not been electrically damaged.

    Regards: Elliott
     
    Last edited: 26 Oct 2015
  4. malice67

    malice67

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    Thanks. It appears to have been wired / connected correctly as it used to work fine...
     
  5. Taylortwocities

    Taylortwocities

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    I'm not sure what you mean by "appears to have been wired correctly"

    Do you have a test meter, or two probe voltage tester? You first must confirm there is actually 230V AC on the mains supply terminals.
     
  6. malice67

    malice67

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    Yep, checked that. There's definitely 230V AC supply. Could it be a fault with the thermostat itself rather than the overall heating system?
     
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  8. eveares

    eveares

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    I presume he means that it the supply and the load is wired to the right terminals as shown by the diagram.

    Malice67; does anything show on the screen or is it 100% blank. As Taylortwocities said, you need to establish if there is power (230v AC) feeding the device by using a two probe voltage tester. Why not ideal, a multimeter would technically do. Just be careful that you have the right range selected and the jacks are NOT plugged into the Amp/Current ports.

    If there is mains voltage on the mains supply terminals; then either 1) your thermostat is likely broken/dead or 2) It is possible the load to the thermostat is shorted out/overloading and is somehow affecting the thermostat from working as it should. 2) Can easily be check by disconnecting the load from the thermostat and seeing if the thermostat works.

    If you don't have mains voltage to the mains supply terminals of the thermostat, then you need to check for blown fuses , tripped MCB's/RCD's and of course any other devices what may be isolating the power such as switches.

    Also, is this being used with electric underfloor heating?, if so you may want to borrow a electrical tester capable of both IR and low resistance testing and perform out what I said to ensure that the heating element is not damaged.

    Regards: Elliott
     
  9. malice67

    malice67

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    Thanks! The 'digits', i.e. 3, 6, 9 etc are showing on the display but absolutely nothing else! I did establish that there is power feeding the device and no, overloading is not possible as it's on a single lead / feed and used to be working absolutely fine last Winter!
     
  10. eveares

    eveares

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    What I was saying was the load on the thermostat such as the underfloor heating element may have become faulty (e.g. through physical stress in the floor over time) and was now electrically overloading the thermostat. Can you please post a picture of what is shown on the thermostats screen as it may help us. (i.e. Is the display flashing any particular digits representing a fault code?)

    Also how old is the under floor heating install?

    The manual for the thermostat can be found here. Trouble shooting info can be found on page 28 of the PDF.
     
  11. Taylortwocities

    Taylortwocities

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    So when you originally said

    You did not really mean that, did you.:rolleyes: Its hard to help unless you tell us exactly what is happening.

    Suggest you have a look at the manual (in the post above) and see if it helps. Otherwise, it looks like it could be a faulty stat.
     
  12. eveares

    eveares

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