Worcester 24ijunior Installation And Servicing Instructions page 29

15 Primary [ch] Sensor
Remove the clip-on facia cover and the cabinet. Lower the facia
onto the support lugs.
Carefully pull-off the connections. Release the clip and remove
the sensor. Refer to Fig. 58.
Do not omit the heat transfer paste when fitting the replacement
sensor.
16 Primary Overheat Thermostat
Remove the clip-on facia cover,cabinet and the inner casing
cover.
Carefully pull-off the connections. Unscrew the two screws and
remove the thermostat and fixing bracket. Refer to Fig. 59.
Apply a small quantity of heat transfer paste to the face of the
replacement thermostat.
Carefully position the thermostat so that the connections are
away from the flue hood.
17 DHW Sensor
Remove the clip-on facia cover and cabinet. Lower the facia onto
the lower support lugs.
Carefully pull off the connections. Unscrew the clip and remove
the sensor.
Apply a small quantity of heat transfer paste to the face of the
replacement sensor. Refer to Fig. 60.
18 Pump
Check that the system valves have been shut and the appliance
has been fully drained. NOTE: A little water will remain in some
components.
Remove the clip on facia cover and cabinet. Place the facia con-
trol panel onto the lower support lugs.
Remove the burner as described in Section 16.4 preceding.
Disconnect the flexible hose at the relief valve assembly.
Pull out the clip to disconnect the pressure gauge capillary head.
Refer to Fig. 52.
Raise and remove the clip securing the by-pass pipe to the cen-
tral heating flow pipe. Refer to Fig. 52.
Pull out the flat clip securing the brass fitting at the top of the pump.
Unscrew the fitting from inside the combustion chamber. Refer to
Fig. 41.
Undo the union connection beneath the pump and carefully
withdraw the pump. Take care when releasing the by-pass pipe.
Support the pump and disconnect electrically.
Transfer the by-pass pipe, expansion vessel flexible connector
and the drain point and pressure gauge connector to the new
pump. Transfer the inlet and outlet connections. Use new O-rings
and seals where necessary.
Reconnect the electrical leads.
Fit the new pump assembly in the reverse order using new O-
rings and seals where necessary.
Do not forget to re-connect the
!
expansion vessel flexible pipe to the
relief valve assembly. Refer to Fig. 17.
IMPORTANT
Alternatively:
Unscrew, using a 4mm Allen to release the four fixing screws,
and remove the pump head. Refer to Fig. 45.
Access is improved if the pressure gauge head and bracket are
temporarilly removed.
Transfer the electrical connections to the new pump head and
set the speed at maximum.
Refit the pump head taking care not to scratch the pump mating
faces.
Open the system valves and re-fill, re-pressurise and fully vent the
appliance and the system ensuring that there are no air-locks.
19 Expansion Vessel
It will be necessary to remove the appliance from the wall to
replace the expansion vessel.
Alternatively the specified replacement can be fitted into the
heating system return as close to the appliance as possible.
Re-fill and pressurise the system as described in Section 13
Commissioning.
Fig. 58. Primary (CH) sensor.
3
1
Fig. 59. Overheat thermostat
2
1
1. Heat exchanger manifold
2. Overheat thermostat
3. Fixing clamp
4. Water pressure switch connection point
Fig. 60. DHW sensor
1. DHW sensor
2. DHW sensor fixing clip
and screw
2
1
29
2
1. Primary Sensor
2. Fixing clip
3. Flow pipe
3
4