Identify a Danfoss Thermostat

[hellsfish]

I need to replace a couple of these Danfoss room stats.
Can anyone identify the mode and know if there is a replacement that fits on the old backplate?

 

[denso13]

It's a Danfoss 087N703800 RET230. What's wrong with them?

 

[ianmcd]

On the most part they are very reliable, as @denso13 asks why are you looking to change them ?

 

[hellsfish]

When the required temperature is increased on the dial, the call for heat light illuminates but there is no corresponding “click” (as there is with the stats that are still operational). There is also no response from the heating system.

 

[denso13]

There is also no response from the heating system.

Can you take the cover off and post a photo of the existing wiring?

 

[ianmcd]

usually when these dont click it means there is a neutral fault

 

[hellsfish]

They are on an underfloor heating system so there are a lot of them in the house. If I swap the thermostat over with one of the ones that are working, the zone is controllable again so I assume that means the thermostat itself is the problem, rather than a problem with the system elsewhere?