Replacement Of Parts; Pcb Control Board And Transformer - Bosch WORCESTER GREENSTAR HE ZB 7-27 Manual

Maintenance
Siphon
y Unscrew the clip and disconnect the pipe to the
siphon.
y Remove the yellow plug to drain the siphon.
y Unscrew the securing nut from beneath the side
facia and remove the siphon. Refer to figure below.
y Refit and prime the siphon.
Condensate
Drain
Siphon
Fig. 54
Expansion vessel
The expansion vessel should be checked once a year.
y Depressurise appliance.
y If necessary, adjust expansion vessel charge pres-
sure to static head of the heating system.
Heating system pressure
Fill the system using the WRc approved
i
filling loop.
y The pointer on the pressure gauge should be 1 bar.
y If the pointer is below 1 bar (when the system is
cold), water should be added until the pointer is
1 bar again.
y Max. pressure of 2.5 bar when the heating system
water is at maximum temperature must not be
exceeded. If this pressure is exceeded then an extra
expansion vessel must be fitted in the system return
as close to the appliance as possible.
y If the system does not retain the pressure, the expan-
sion vessel and the heating system should be
checked for leaks.
Electrical wiring
y Check the electrical wiring for physical damage and
replace any damaged wires.
36
8.3
Before changing any components check that the gas is
turned off and that the appliance is electrically isolated.
When necessary close the system valves and drain the
appliance.
Refitting is a reverse of the procedure for removal using
new seals or o-rings as appropriate.
8.3.1
y Switch off the appliance.
y Disconnect appliance from the power supply.
y Unplug all connectors from the control box (inc.
keyed plug). Access is gained by removing the cov-
ers. Refer to fig. 24, 25.
y Remove screw holding power connector earth lead
and remove earth lead.
y Remove two top fixing screws from the control box.
Refer to fig. 55.
6 720 610 602 - 16. 1O
Fig. 55

Replacement of Parts

PCB control board and transformer

6 720 610 596 GB (01.07)