Devireg 535 thermostats turning off

[DerekPCB]

Hi folks,

My daughter has moved into a new house where it's underfloor electric heating. There are wall thermostats (Devireg 535). She tells me the thermostat have a red/green LED and is lit when the heating is on, but at times, the thermostat will just switch off (including LED) and display. I checked with her, no fuses are tripping in the consumer unit.

I'm not sure if it's schedules turning the entire unit off, or something could be wrong. They'll power on for some time and completely switch off after awhile. We are expecting the thermostat to stay on, at least the display at all times. Is that how these units work?

This appears to be the case for several thermostats not just one.

Any ideas gents?

Thanks

 

[CountryFan]

Is it not just reaching temperature?

 

[DerekPCB]

Indeed after more testing, it appears heating is working and the room is getting up to temperature.
She was confused why the entire unit was powering off with no method to wake it. Then it comes back on randomly, or now I believe when the temperature has fallen below the thermostat point.
Still have not confirmed if this is expected behaviour.