Hi,
I have a problem with an intermittant, mildly alarming, Ker-Lunk sound from the central heating when the room thermostat cuts out (i.e. stops calling for heat)
System is Honeywell S plan, with two dual port valves, Boiler is an Ideal Classic FF 280, about 10 years old now.
There is a pressure-opening valve in the loop-back circuit (I understand this is supposed to open when both dual-ports are closed and the boiler is still pumping?). It's set between
2 and 3 on its dial (which goes up to 9).The noise does not happen all the time, but when it does, it is noticeable and LOUD.
Suggestions as to what's going wrong will be much appreciated.
--Mike