Tony, you might want to read the thread top to bottom and then review what you have written above.
I see no point in using the clamp thermometer until the outcome of what I ask has been posted.
OP, your boiler will display the temperature of water at the outlet of the main heat exchanger when you run central heating. For hot water, it displays temperature of water supplied to the taps. It will NEVER get to 90+.
When you ask for hot water, boiler display shows the hot water temperature which in your case never rises above 40 at which the burner shuts down. What you are not SEEING at this point is the temperature of water at the outlet of the MIAN heat exchanger (it is this water that INDIRECTLY heats the water that comes out of the hot tap). The heat produced by the main heat exchanger must be utilised by the heat exchanger that heats the water for your taps. Therefore, heat out at main heat exchanger equals heat in at hot water heat exchanger (there is control involved to tweak heat out to match within reasons heat in at the HW heat exchanger). To recap, if main heat exchnager produces 30kwatts of heat, hot water heat exchanger uses that 30kw of heat to give you hot water.
IF the main heat exchanger produces 30kwatts of heat, and your hot water heat exchanger only takes in 20kwatts of heat because it is partially blocked, then the sensor on the outlet of the main heat exchanger see temperature rise beyond its control and shuts the burner down or it would very quickly go critical and water would be converted to steam and possibly cause system damage.
What I suggested you do is run central heating, then run a hot tap. When burner goes out and display is at its HW peak temperature. Flip the aforementioned valve to 9.00 o'clock and see what the display indicates. The moment boiler comes out of hot water mode and reverts to heating mode, the display TOO reverts to showing the primary water temperature. This is the figure that interests me.
I see no point in using the clamp thermometer until the outcome of what I ask has been posted.
OP, your boiler will display the temperature of water at the outlet of the main heat exchanger when you run central heating. For hot water, it displays temperature of water supplied to the taps. It will NEVER get to 90+.
When you ask for hot water, boiler display shows the hot water temperature which in your case never rises above 40 at which the burner shuts down. What you are not SEEING at this point is the temperature of water at the outlet of the MIAN heat exchanger (it is this water that INDIRECTLY heats the water that comes out of the hot tap). The heat produced by the main heat exchanger must be utilised by the heat exchanger that heats the water for your taps. Therefore, heat out at main heat exchanger equals heat in at hot water heat exchanger (there is control involved to tweak heat out to match within reasons heat in at the HW heat exchanger). To recap, if main heat exchnager produces 30kwatts of heat, hot water heat exchanger uses that 30kw of heat to give you hot water.
IF the main heat exchanger produces 30kwatts of heat, and your hot water heat exchanger only takes in 20kwatts of heat because it is partially blocked, then the sensor on the outlet of the main heat exchanger see temperature rise beyond its control and shuts the burner down or it would very quickly go critical and water would be converted to steam and possibly cause system damage.
What I suggested you do is run central heating, then run a hot tap. When burner goes out and display is at its HW peak temperature. Flip the aforementioned valve to 9.00 o'clock and see what the display indicates. The moment boiler comes out of hot water mode and reverts to heating mode, the display TOO reverts to showing the primary water temperature. This is the figure that interests me.
