My old netaheat 16/22 is still going strong after 22+ years. But it has developed a problem over this last winter. The fan runs, the ignitor fires, the pilot flame starts, then its a long time 4 or 5 mins before the boiler fires up. It then heats normaly switches off when boiler temp is reached. but then takes again 4 or 5 mins to restart. Any body, any thoughts ??

Chris Edwards, January 2007

You've been lucky if your mercury vapour valve has lasted for 22yrs! I've had to replace 3 so far - but the boiler is in its 30th year! BTW the part IS expensive (£200+) so be prepared for a big repair bill.

Algynon, January 2007

its the mercury expansion valve which is heated by the pilot and plugs into the end of the gas valve is on its way out. you need to take the case off to replace so call a CORGI engineer to fix it.

Paul the gas man, January 2007