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Problem with thermostats

Discussion in 'Plumbing and Central Heating' started by Mark Tyler, 14 Oct 2021.

  1. Mark Tyler

    Mark Tyler

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    Hello,
    I bought 3 thermostats from Aliexpress, model BHT-002 GA as it should have fit underfloor water heating.
    The problem is, all 3 of them do not work. They work as if, the display is operative, but when the heating is on, it does not short contacts 1&3. I hear the relay clicking. I checked with multimeter, there is current on 3&4 but never on 1&3.
    For the wires on the wall: green is L, blue is incoming N, brown goes to N wire on water pressure valve. The second wire on each valve goes to L directly. So if i short brown & blue on a wall, valve corectly opens, so the wiring is fine. The valves are NC (normally closed).
    The strange thing is that all 3 thermostats do not work, so its really strange.
    Do they seem defective? Or I bought incorrect model?
     

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    Last edited: 14 Oct 2021
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  3. muggles

    muggles

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    If you short brown & blue and the valve opens, that suggests brown & blue are both Live and the green/yellow is Neutral, but you've wired it up with green/yellow as your permanent live and blue as your neutral. Can you show the connections in the wiring centre at the other end of the thermostat cable?
     
  4. Mark Tyler

    Mark Tyler

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    It’s rather complicated, i can try to make a wiring scheme. There are 5 thermostats in the house, but 3 of them are shorted together (first floor large room had 3 thermostats so it was not necessary). Old thermostats did work, but i changed wiring since then.
     

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  5. Mark Tyler

    Mark Tyler

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    Here is a diagram of wiring. Thank you!
     

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  6. DP

    DP

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    First thing I would be doing is correct the conductor colours with sleeves so there is NO doubt what the conductor is meant to do. It Is always prudent to use correct cable with adequate number of conductors to reflect what it is carrying.

    You do not have three faulty stats but you appear to have wiring issues.

    It is the live conductor that should get switched, not the neutral
    In your diagram you you have live one side of the load and switched live on other side of the load too

    That thermostat needs live and neutral to work ie power needs to go to L and N to get live feed out to do its thing.

    My advice to you would be leave wiring to someone who understands as you will either hurt yourself or someone who comes to your aid
     
  7. Mark Tyler

    Mark Tyler

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    Ok, but on the thermostat judging by the electrical connection, it is the N which is switched as you can see in attachment. Should i flip them anyway? Also I cannot change the colors of the cables, as they are in the wall already.
     

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  8. bernardgreen

    bernardgreen

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  9. Mark Tyler

    Mark Tyler

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    Sorry, maybe i didn't understand, but this is exactly how it is wired in my case. Only i use pin 1, as it is for NC valves (i tried 2 anyway, but it still doesn't work). The 4 (L) is live wire, testing screwdriver lights up when touching it.
     
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  11. bernardgreen

    bernardgreen

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    upload_2021-10-14_8-38-39.png is the water valve and NOT the internal switching of the thermostat.

    The switch in my sketch is the switch ( relay ) inside the thermostat. It is the LIVE that is switched inside the thermostat
     
  12. Mark Tyler

    Mark Tyler

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    Oh I seen now! So I need to change the wiring. Could you please double check if I applied it correctly for my case?
     

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  13. bernardgreen

    bernardgreen

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    upload_2021-10-14_9-56-8.png

    I like the use of the symbol for an electronic rectifier valve.
     
  14. Mark Tyler

    Mark Tyler

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    Yeah, i just picked the symbol because it looks like valve and has two connections :) anyway, thanks for the help, i will rewire cables later.
     
  15. Mark Tyler

    Mark Tyler

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  16. DP

    DP

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    So others that said the Same thing did not make sense to you. And obviously you did not have three faulty stats also you do not know your green and yellow from brown or blue conductors. What has cables in the wall got to do with it to correct the colour.
     
  17. bernardgreen

    bernardgreen

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    I think I was the first to make the point that [​IMG] was the water valve and NOT the internal switching of the thermostat

    Printing that circuit diagram on the the thermostat is misleading
     
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