Bosch WORCESTER Greenstar Heatslave II External 12/18 Installation, Commissioning And Servicing Instructions page 58

Fault finding and diagnosis
Is the system pressure constantly increasing even
when the boiler is off for extended periods of time?
Does system pressure
increase when the
boiler is on?
NO
Is the system pressure regularly
dropping (i.e. you constantly
have to top up your boilers pressure)
NO
YES
Does the PRV
The
regularly drip?
boiler
is
fine
NO
Check
the CH
system for
leaks
Fig. 108
58
NO
YES
Does the system pressure increase to
the high pressure red zone on the
pressure gauge?
NO
Is the Expansion
The
Vessel pre-charged
boiler
higher than expected
is
fine
YES
NO
Is the Expansion
Check/
Vessel pre-charge
replace
too low?
PRV
NO
Check
Expansion
Vessel is sized
correctly for
the system
PRV = Pressure Relief Valve
EV = Expansion Vessel
YES
Can you confirm that the filling
link is not stuck open/passing
water in any way?
Confirm the filling link is
YES
closed and check that the
Plate Heat Exchanger
is not cross leaking
heat exchanger
YES
NO
Do the radiators
have to be
regularly vented
YES
YES
Re-
pressurise
Corrosion
the EV
is probably
occurring within the
heating system which
is causing system
gassing.
The system should
be cleaned
and treated to
comply with
BS 7593
Greenstar Heatslave II External
NO
YES
Does the
problem
persist?
YES
Is the plate
leaking?
YES
Replace
Plate Heat
Exchanger
NO
Most
likely a
cross-leaking
component in
the boiler.
Further
investigation
required
0010036323-001
2022+ 6 721 843 980 (2022/01)
NO
The
boiler
is
fine