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