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Posted by Harold hydronicnetwork.net on November 22, 2003 at 12:59:20:
In Reply to: Re: Aquastat posted by Brent on November 22, 2003 at 09:43:44:
Some of the old models used mercoid controls that had larger sensors than the 5/16, 7/16, 3/8 sensors of the later controls. Some used the smaller sensors with a sheet metal flat spring insert with the compound, though these were not as accurate.
If you don't want to drain the boiler to install a new sensor well, you might get a machinist to lathe a brass or aluminum rod inset that has the outside dimension of the well and the inside dimension of the sensor (plus 1/16th). Then he can cut it in half the long way so both halves insert easily into the well with the aluminum compound lubricating them.
It is better to use a new well that inserts into a tapping near the boiler top so the sensor is reading the water temperature surrounding it rather than inside a more remote pipe.