Fitting Thermostat To Hot Water Cylinder

[paulfg]

I have a close coupled solar panel with horizontal water cylinder mounted directly above it.
I need to fit a thermostat to sense the hot water temperature and control the central heating boiler coil input.
There is only one place for a thermostat that I can see that is in the middle of the immersion heater element and controls the immersion.
Is it possible to fit a digital thermostat like a PT100 or NTC into a thermowall via a tee on one of the water in/outputs to be able to monitor the tank water temperature.
If so where is best ?
Suggestions on thermostat welcome

thanks in advance

 

[Last Plumber]

Sounds like you're on continent?
Roof top cylinder ?
Like you see in Portugal ?

 

[paulfg]

yes I am in Corfu Greece,i am thinking maybe a capilary thermostat with the tube pushed down against the cylinder between the wall and the foam insulation under the immersion heater access cap.
There is room for the thermostat body inside the opening to access the immersion element and I hope the capilary tube will work if I make sure it is in contact with the cylinder wall.
I basically have a solar panel with a heating loop I wish to connect to my woodburning fire/ boiler,to top up on dull winter days.The controller has the facility to give hot water priority by the closing/opening of an electrical circuit (basically a loop acrss two terminals)
i do not want to disconnect the immersion as it is a final backup for hot water if I dont want to light the fire/boiler ,say on a dull summer day

 

[paulfg]

bump
I have found out the hot water tank is surrounded my a water jacket that is used by the solar panel as the heating coil.
The only access to the actual domestic hot water part is the flange mounted immersion element which has a thermostat fitted to control the immersion.
I could disconnect the imersion and use that to control the vale from the woodburning fire/boiler but the I cannot use the imersion.
My idea of a capillary thermostat wont work unless I can find a way to fix the bulb to the flange or fit a thermowall on the flange.
Any ideas ?
Are there such things as imersion thermostats with a set if auxillary contact that can be wired to control another device?

thanks