John Smith wrote:
On 2020-10-08 10:24:50 +0000, John Rumm said:

Quite possibly - but it also explains why a number of installations
seem to work in practice, even when they their supply pipework is well
out of spec.

So our new Vaillant has conked out tonight after working perfectly for
a week. Won't fire up, just like the old Vaillant now scrapped, which
also failed on a Friday evening.

I presume youve checked the system pressure (assuming its a sealed
system)?

Tim

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Please don't feed the trolls