Posted by Harold Kestenholz - Hydronic Network on August 03, 2000 at 12:56:58:
In Reply to: Vaillant domestic water too hot! posted by Clive Oldfield on August 03, 2000 at 02:14:31:
With some clues, there is a logic chain:
If one sensor does both heat and hot water - the hot water control circuit has a problem, but not the heat control circuit.
If a different sensor does the hot water, that control circuit can have a problem.
OR
The domestic water flow rate may have been reduced through clogging, and the sensor may have become less sensitive due to the insulative value of the fouling in that area. Heating application is a slower process, so it is affected less by fouling. European companies do an annual teardown and cleaning, not the habit in North America.