Morning all woke up this am to find the house power was off. Main MCB had tripped. Flicked it back on; all seems OK.
Until we try to use the manual override on the CH programmer - a Sunvic Select 207XL - to put the radiators back on. Then the MCB trips again. This is repeatable.
We have a gravity fed system and manually switching the HW only on works OK.
I am shortly going to investigate. There's clearly only a couple of things that can have gone wrong (famous last words). Comments on probability of controller failure gratefully received. Recommendations for an alternative?
Thanks Jon N