Negative temperature coefficient. If cable has not come away from sensor thermistor, make sure you have min pressure around 0.7 bar I found on that, switch off for 5 secs, turn on, you may find fault 19 disappear.
Shallow heating.
April 2012
try a ntc.
negative temperature co-efficient thermister.
it's a sensor connected to a pipe
hi-spec plumbing & heating
January 2008
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