I have a Potterton Suprima 60L boiler. When the HW (only) comes on, the gas ignites. After about a minute, the red LED comes on with green LED flashing (to indicate there is no longer a demand for heat) and gas is extinguished. Shortly after that the red LED goes out with green still flashing (so demand for heat). After about 3-4 mins the boiler ignites and repeats the process.
Needless to say it doesn't manage to generate much hot water in the process. The thermostat is set to about half-way (although I've tried it in min/max combination also). I'm not convinced it is necessarily the PCB, because I'm not getting the red-flashing lock-out that seems to be common with these boilers.
If HW is on together with CH, then everything seems to work much better (stayed on for approx 15 mins after 25 mins of just HW cycling) and I get hot water/radiators (so I don't think it is a problem with the hot water tank). I had a heating engineer come to do a service and he reckons that everything's set-up OK (he was the one who put me on to the PCB problems).
Any ideas? Is it worth replacing the thermistor? Surely the motorised valve defaults to HW, so it can't be that? Any other diagnostics I can do?
Needless to say it doesn't manage to generate much hot water in the process. The thermostat is set to about half-way (although I've tried it in min/max combination also). I'm not convinced it is necessarily the PCB, because I'm not getting the red-flashing lock-out that seems to be common with these boilers.
If HW is on together with CH, then everything seems to work much better (stayed on for approx 15 mins after 25 mins of just HW cycling) and I get hot water/radiators (so I don't think it is a problem with the hot water tank). I had a heating engineer come to do a service and he reckons that everything's set-up OK (he was the one who put me on to the PCB problems).
Any ideas? Is it worth replacing the thermistor? Surely the motorised valve defaults to HW, so it can't be that? Any other diagnostics I can do?