Bosch Worcester 240 Combi OF Installation And Servicing Instructions page 22

Fig. 27. Circulating pump.
The maximum burner pressure must be set first, as any adjust·
ment of the maximum pressure influences the minimum pres·
sure setting.
Remove the the fixing screw and remove the the Modureg cover.
The Modureg cap must be replaced immediately the adjust·
ments have been made to ensure the proper operation of the
gas control.
Start the appliance
in
the domestic hot water mode as described
in
Section 12.4- Appliance Operation.
Adjust the maximum pressure adjustment nut to give a burner
pressure of 14.4 mbar. See Fig 18.
Switch off the appliance and turn off the electricity supply.
Remove a lead to the Modureg head.
Fig. 28. Expansion vessel and pump
assembly.
22
Switch on the electricity supply to the appliance and re-light in
the domestic hot water mode. The burner pressure will remain
at the minimum setting.
'Illm the minimum pressure adjustment screw until the burner
pressure
is
2. 9 mbar. See Fig.18.
Switch off the appliance and tum off the electricity supply. Refit
the lead to the Modureg head.
15. Central Heating Senso~
See
Fig. 26
Check that the electricity supply
to
the appliance is turned off.
Remove the cabinet front panel as described in Section 14.3(a).
Carefully pull off the two leads from the sensor. Loosen the two
M3 screws securing the sensor to the fitting and remove the
sensor
Fit the replacement sensor with a layer of heat sink compound
between the faces. Refit the leads.
16. Domestic Hot water
Senso~ See
Fig. 26
Check that the electricity supply to the appliance is turned off.
Hang the control box assembly in the servicing position as
described in Section 14.3(d).
Carefully pull off the two leads from the sensor. Loosen the two
M3 screws holding the sensor to the fitting and remove the
sensor.
Fit the replacement sensor in the reverse order ensuring a layer
of heat sink compound is between the faces. Refit the leads.
1 7. Circulating Pump.
See
Fig 27
Check that the electricity supply to the appliance is turned off.
Drain the appliance as described in Section 15.3(a).
Hang the control box assembly in the servicing position as
described in Section 14.3(d).
Undo the two union nuts and remove the pump from the pipe·
work. Support the pump and remove the electrical cover. Discon·
nect the electrical wires taking note of their positions.
Fit the replacement pump in the reverse order using new sealing
washers. Ease back the sleeved connector to allow the fitting of
the bottom washer.
Alternatively replace the pump head only by removing the four
Allen screws. ·
Open the valves and fill and re-pressurise the system as described
in Section 12.2.
Note. The direction of flow should be downwards. The speed
should always be set to maximum.
1 8. EXpansion Vessel.
See
Fig 28
Drain the central heating circuit as described in Section 15.3(a).
Hang the control box assembly in the servicing position as
described in Section 14.3(d).
Remove the gas valve as described in Section 15.14.
Undo the expansion vessel connection at the boiler flow connec·
tion and remove the vessel.
Fit the replacement vessel in the reverse order.
Open the valves and fill and re·pressurise the system as described
in Section 12.2.
19. Pressure Relief Valve.
See
Fig 1 7
Drain the central heating circuit as described in Section 15.3(a).
Lower the control box assembly as described in Section 14.3(d)
Undo the discharge pipe connection and the pressure gauge
connection. Unscrew the valve taking care not to distort the
pipework.
Fit the replacement valve using a suitable thread sealing com·
pound. Reconnect the discharge pipe and pressure gauge.
Open the valves and fill and re·pressurise the system as described
in Section 12.2.