The boiler has not powered up since.
As the temperature plummeted to five degrees, we thankfully had our two backup Dragon oil heaters, the living room gas fire and the electric immersion heater. We've been surviving thus for four days.
|Cowering around the gas fire as temperatures plummet|
This afternoon the plumber - who has stated in advanced that he's not a specialist in the Bosch Worcester Greenstar 30CDi gas-fired condensing boiler - will be popping around to see if he can reboot the system. It's seven years old and well out of warranty.
Update 7 pm: Steve Abbott arrived and soon figured out that the boiler overflow valve had jammed open. It's hard to get at, but he popped it back and rebooted the boiler. After bleeding air out of some of the radiators (they had also lost water to the uncontrolled venting) the heating kicked back in and the house began to warm. The Germans probably have a name for that unique psychological state you feel as a radiator begins to warm under your hand on a freezing night.
The proximate cause of all this messing around was the leaking/blocked taps, still unfixed. Steve will be back soon to repair/replace those and do a quick overall diagnostic test of the boiler.
I had slightly forgotten how impressive expertise in action actually is.