Hi mate, and thanks for this.
What I should have mentioned and forgot peeps don't always remember what I post in such detail is that the system is an underfloor heating system. NOT a WET one.
Each room has heating coils or cables in a special sort of concrete which sits below the floor tiles.
Each room or area has it's own stat. 11 in all I think.
Over a period of time they have started failing one bhy one. When you try to make one work the little red light just clicks on and off . They come in two parts, one sits in a box in the wall the other is the face plate. I have tried swoppoing face playtes from known good working ones and it makes no difference so I know the problems always lie with the hidden unit. It has at least three capacitors, two small cylindrical ones and one larger oblong yellow one. I suspect that this is where the problem lies but as you know I am now electronic engineer.
So In the past I have replaced two with modern versions of the originals. They even have the same make and model number but they now have LCDs and even more complexity and they are flipping expensive, €40 euros each and that was a few years ago!
So I am trying to replace them with much simpler bimetallic ones.
If I can get this one to work then I have found ones on the net far, far cheaper.
All they need to do is act as stats. They don't even need to do on-off, I can do that from the consumer unit.
So each unit's load wire goes off to a relay that switches power to the huge underfloor cables. Or does it? Does the neutral wire do it as well? This is the massive question I am trying to get my head around.
You need to speak to me in extremely simple terms.
And I can see while I have been typing this that you have added another couple of posts that I have yet to read.
Thanks for your help mate
Ur so welcome my friend
Ah , I see so u have electrical mat UFH, must confess never really dealt with electric UFH, but did do a vast amount of wet UFH that had manifolds to control each zone
Saying that it sounds similar in u have a room thermostat in according zones, that when it’s set to call it triggers a relay and therefore turns that particular zone on
Very similar to a wet UFH, where the room thermostat which open a valve actuator and therefore allow the hot eater to enter that zone
So the stats are just a make and break circuit to each relay and then onto the mat zone
When I had faults I would use a multimeter and test live in and back out , following the circuit towards each zone , so when for example a room thermostat would work I would link it out and carry on towards to the activation valve or in ur case the relay if I’m understanding it correctly
if ur unsure With an electric Matt I would assume u could find each end of the wires that go to each Matt and do a continuity test ,
So indeed should be easy to follow power or continuity from the thermostat to eaxh UFH mat
Hope that makes sense