i have a thelia 623 combi.the hot water comes through only warm i have slowed the water rate down as much as possible but the flames seem to die down when i turn the hot tap on and increase again when it goes back to central heating.
I have the exact same problem. Thought it was a thermostat but that doesn't seem to help. I have been advised to replace the circuit board, but not sure that will fix the issue.
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