Thanks Dave. The last few hours have been very educational on CH systems! I am now hunting down this valve!
...but would this explain the erratc nature of the system (sometimes it works perfectly, sometimes not at all).
- Mark
We moved this summer and the gas CH system is driving us nuts. (It's not a new house)
The boiler is a Worcester Greenstar 24Ri regular boiler, fitted in the garage, with a thermostat in one room and a Wickes/Siemens RWB9 controller in another room. Radiators have thermostatic valves.
Under...