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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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.

  • I like this idea... simple, undo-able. One concern is that the thermal grease will be on the surface preventing the silicone from adhering... – UuDdLrLrSs Dec 5 '19 at 2:29
  • If you coat the sensor with a thermal grease ( a really good idea) the grease is more of a plug, kinda like a rubber stopper in a bottle, grease keeps the rubber from sticking to the glass or metal in your case but a plug helps to hold the wires or cable in the hole, as I said I do this on equipment that moves at my plant. At home I seal fire rods , low power to keep things from freezing / condensing moisture that could cause problems as I have posted in the past. – Ed Beal Dec 5 '19 at 3:01

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