Devi touch working but floor not heating up

[Gillimarie54]

Hi
We have Devi mat underfloor heating in our conservatory. We had a new touch controller three years ago.
The first few times I tested the system this winter all was well. It was coming on over night on our Economy 7. Then three nights ago the floor didn’t heat up.
I checked everything and for three nights the floor temperature just got colder.
The touch shows all the correct settings and appears to be heating up the floor. No error messages. I forced it to operate during the day by turning the timer off.
But our in house display for our meter showed no response for electricity being used.
I tested the kitchen in the same way and the display immediately showed us using 770w until I turned it off.
So definitely no heating is taking place on the other floor.
As all is set up correctly and the little moving arrows apparently indicate heating is taking place, I’m not sure what could have happened.
Any ideas?
Has it just failed? There are at least three mats under the tiles so it’s odd they are all off. But it’s not a spring chicken either. It’s approaching 20 years old. Maybe expecting too much of its lifespan.
On the other hand, it’s only used overnight in winter and on frost protection the rest of the year. We leave the control on. So it’s not been hammered. Never on longer at night than the Economy 7 hours. And when the controller failed we didn’t use it for a few years. But it’s been working well for the last seven years at least.
Any suggestions gratefully received.

 

[Madrab]

You need to test the circuit - Voltmeter on resistance - the power needs isolated, the mat needs to be disconnected from the controller and then tested for resistance. If there's a nul/no reading the mats circuit has failed and it'll need replaced.

 

[Gillimarie54]

Thank you. We have an excellent electrician who we regularly use. This sounds like something he can do for us. He fitted the two new controllers in the kitchen and conservatory and he will be able to carry out the test you are suggesting. If the mat circuitry has failed, I’m thinking that’s it. Not a repair job. We always knew that it being under a tiled floor was a risk. But unless it’s the repair I’ve seen written about elsewhere on here where you just need to take a tile up, I’m thinking it’s served its time. It’s a big conservatory and the underfloor hearing made a perceptible difference in the winter. We have radiators, but the underfloor acted like a big storage heater during the day. It’s a big room. 24ft long and the width of our semi. We use it all year. I can’t imagine the cost to replace it now we are retired. I guess the cheapest would be to just go again on top of the existing tiles rather than digging the whole thing up. Or we could just use a few area rugs to make it warmer under foot.
Really appreciate your reply though. We will start with that test.