My heating system has a tankless boiler which feeds an external tank. The tank temperature is measured using a probe inserted into a standard aquastat well.
The probe is considerably smaller than the well diameter. It is supposed to be filled with thermal grease to aid conductivity. But how to effectively keep the sensor in the well? The well doesn't have any sort of cap or fitting to close off the open end.
I could obviously just tape it but I'd like to find something more permanent than that. Tapes often dry out. I'd thought of heat-shrink tubing but I think the difference in size from the small wire to the large metal tube is too much.
Well with probe inserted:
Well and probe itself: