Forget limescale...highly unlikely.
It's the primary side that's prone to blocking....tends to be flakes blocking up the left hand port or a thin layer of sludge throughout the plate surfaces. Easy to measure differential temperatures across it to determine whether this is the actual fault.
Sensors often fail by going open circuit at a particular temperature. Once this happens burner may extinguish...sensor cools and burner re-ignites.
Just keep calling BG...record for one of my customers is 29 visits
It's the primary side that's prone to blocking....tends to be flakes blocking up the left hand port or a thin layer of sludge throughout the plate surfaces. Easy to measure differential temperatures across it to determine whether this is the actual fault.
Sensors often fail by going open circuit at a particular temperature. Once this happens burner may extinguish...sensor cools and burner re-ignites.
Just keep calling BG...record for one of my customers is 29 visits