Could anyone please tell me the problem with this boiler - it's Calor Gas and has had a new valve fitted to try and solve this problem which was worse with the old valve. Sometimes when the boiler first starts up the main burner flame 'roars' and burns yellow, up the back of the boiler I think, causing overheating. If I switch it off and back on again it usually reignites and burns normally blue.
Gheck VERY carefully that the burner jet mounting plate cork gasket between this plate and the mounting is intact, the jet mounting is evenly seated and the four screws are holding it flat. Sounds as though there may be a weep of gas escaping and forming a secondary flame outside the combustion chamber back wall. This can and does happen and often melts off the solder holding the overheat stat wires in place on older models. Does the boiler no good at all!
It might be that somehow the gas is being ignited as it comes out of the injectors not as it emerges from the burner ports.
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