Vaillant EcoTec Plus Stove - Error F76 Displayed, Water Heating Issue: Causes & Fixes

This sensor is an exhaust gas "sensor".
Thermic sensor.
It is not in contact with water.

After a sensor failure, it is worth doing an exhaust gas analysis to assess whether the exchanger is OK.

raceman wrote:

1) You said you need to drain the water, which is not true!

Yes, for the sake of safety, a layman should do so, because we do not know what or how (you cannot predict everything and write a litany about everything, so by the way).
After all, it was not written that it was checked, he also mentioned it:

ls_77 wrote:

The heat exchanger may become unsealed and water with CO may get into the combustion chamber and further into the sewage system through the condensate drain.

raceman wrote:

2) In our case, the sensor did not break permanently, but behaved unpredictably.

If there are symptoms like you indicate jt. damage to the temperature limiter, in this case TSD 1902. Do not suggest to the author that he "did not break" and "only behaved unpredictably", thus you may expose him to further damage to the boiler in the future and possible costs associated with it. The cause of this should be found and replaced if necessary, it is the safest solution for the user.

raceman wrote:

3) I asked what this sensor measures, you just repeat the mantra STR, STB.

Again, it is (a fuse) an over-temperature limiter, it is not a sensor in the sense of a sensor, e.g. PTC, NTC, Pt 100, Pt 1000 etc. and this is a significant technical difference.
(For your understanding and use, the TSD 1906 may be conventionally referred to as a sensor!)
He also clearly explained it to you in # 3 that it is STB and further:

501toyota wrote:

It is a safety system that is to function in such a way as to prevent accidents, so any interference by inexperienced people can end in a tragedy.

raceman wrote:

Have you ever seen this cauldron with your eyes and undressed?

You are not the author of the topic, do not look for a dispute, so forgive me for answering only in the topic and for the purposes of the author of the topic.

ROWE wrote:

Yes, for the sake of safety, a layman should do so, because we do not know what or how (you cannot predict everything and write a litany about everything, so by the way).
After all, it was not written that it was checked, he also mentioned it:

do you read what you write

ROWE wrote:

You are not the author of the topic, do not look for a dispute, so forgive me for answering only in the topic and for the purposes of the author of the topic.

The author of the topic wrote 4 years ago and hasn't even logged in since then.
So we can assume that the answers apply to the person who unearthed the topic instead of assuming theirs.

The topic is considered exhausted, so I close it.