Plumbing – How to seal an aquastat sensor well

aquastatheatingplumbing

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:

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Well and probe itself:

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Best Answer

I would use some silicone sealer; not a lot, but enough to stick the cable to the well. I do this on heater blocks for electric valves: when the heat rod fails, the silicone is easily removed. Your temperature probe would work the same.