I have a Worcester Heatslave 9.24 RSF combination boiler to heat my
one floor three bedroon flat.

I have had to drain and replace a diverter valve.

The expansion vessel should be prepressured to 0.5 and would like to
check this but have some questions at what stage should the 0.5 bar be
read.

Q1. What is the correct proceedure in pressurising the expansion
vessel. Before the system is pressurised with water or after, or does
it matter.

Q2. Will the expansion vessel pressure reading be different if the
system is filled and pressured with water. ie. if the system pressure
is 1.2 bar should the pressure at the expansion vessel read 1.7 bar
(0.5 expansion pressure + 1.2 system pressure)
OR will the expanison vessel read 0.5 regardless of the system
pressure?

Chris...