Work-from-home positive: Discovering our boiler doesn't work eight hours sooner than i woulda otherwise.
Work-from-home negative: My workplace has no heat or hot water.
Heat is back! Air bubble in the water line.
No idea why there was an air bubble in the water line. That, um, shouldn't happen. Anyway.
Onward!
@bikepedantic did you have to get a bleed kit to fix the problem? Sounds familiar.
