Problem with thermostats

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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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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?
 
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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Here is a diagram of wiring. Thank you!
 

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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
 
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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it is the N which is switched as you can see in attachment

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
 
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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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.
 
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.
 
I think I was the first to make the point that
upload_2021-10-14_8-38-39-png.246912
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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