Potterton Kingfisher Mf 40-100, installed late 2001. CH is pumped. Hot water is gravity fed. Return for both is piped via the pump, which I suspect results in increased resistance to the HW only flow. Some kettling noise, which I suspect is due to limescale build up in the boiler, although I live in a predominently soft water area. Kettling appears greater when boiler set to HW only. System has been chemically cleaned within the last year, all radiators removed and flushed out and pipework flushed separately (not power flushed). Noise reducer and inhibitor added subsequently.
Problem - when set to HW only, system appears to 'boil' and expels hot water into expansion tank within a few minutes. This is accompanied by considerable amount of banging within the pipes. To confirm, this doesn't happen when both CH & HW is on.
Both the thermistor and potentiometer have been replaced by a qualified CH engineer. However, this hasn't provided a resolution to the problem.
Help / advise anybody please.
Problem - when set to HW only, system appears to 'boil' and expels hot water into expansion tank within a few minutes. This is accompanied by considerable amount of banging within the pipes. To confirm, this doesn't happen when both CH & HW is on.
Both the thermistor and potentiometer have been replaced by a qualified CH engineer. However, this hasn't provided a resolution to the problem.
Help / advise anybody please.
