Worcester 24CDi Installation And Servicing Instructions Download Page 18

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should be fitted as shown in Fig. 6,6a.
Insert the bayonet end of the filling key into the corresponding cutouts
in the filling loop housing and twist to lock the key in place.
Turn  the  grey  knob  anti-clockwise  to  allow  water  ingress  and  fill  until
the pressure gauge reads 2.5 bar.
Turn  the  grey  knob  clockwise  to  stop  filling  and  remove  the  filling  key
by  lining  up  the  bayonet  end  of  the  key  with  the  cutouts  in  the  filling
loop housing and withdrawing the key.

N.B. The key must always be removed from the filling loop housing
after the system has been filled to prevent accidental filling and to
comply with Byelaw 14 of the Water Byelaws Scheme.

Store the key in a safe place for future use and refit the bottom panel.
The automatic air vent will vent the appliance. Check that the air vent
cap has been loosened. See Fig. 18.
Check that the pressure relief valve operates by turning the knob anti-
clockwise until it releases. Water should be expelled from the discharge
pipe. See Fig. 27.
Lower the facia panel to gain access. Refer to Section 15.3, c.

Set the Expansion Vessel Pressure

The  charge  pressure  of  the  expansion  vessel  as  dispatched  is  0.5  bar,
which  is  equivalent  to  a  static  head  of  5  metres  (17  ft).  The  charge
pressure  must  not  be  less  than  the  static  head  at  the  point  of
connection. A Schraeder type tyre valve is fitted to the expansion vessel
to allow the charge pressure to be increased if necessary.

Set the system pressure

Release water from the system using the relief valve test knob (see Fig.
27), until the system design pressure is obtained, up to a maximum of
1.5 bar.
Initial system design pressure (bar) = Expansion vessel charge pressure
+ 0.3 bar.

NOTE:

1 bar is equivalent to 10.2 metres (33.5ft) of water.

Set  the  movable  pointer  on  the  pressure  gauge  to  coincide  with  the
indicating  pointer  giving  a  permanent  record  of  the  set  system
pressure.
If the pressure indicated on the pressure gauge is greater than 2.6 bar
when operating at the maximum central heating temperature, an extra
expansion  vessel  must  be  fitted  to  the  system  as  close  as  possible  to
the appliance central heating return connection.
The  appliance  (as  dispatched)  can  accommodate  a  system  volume  of
about 83 litres. Refer to BS 7074 Part 1. If the system volume is in excess
of  that  accommodated  by  the  expansion  vessel  fitted  to  the  appliance
then  an  extra  vessel  must  be  fitted  as  close  as  possible  to  the  central
heating return connection of the appliance.
Any  extra  vessel  fitted  must  be  pressurised  to  the  same  figure  as  the
integral  vessel.  If  the  expansion  vessel  fails  then  the  specified
replacement must be fitted.

13.3 PROGRAMMER

Any programmer fitted on the appliance should be set up at this stage
following the instructions sent with the programmer.
The programmer will retain the settings for up to three weeks following
an interruption in the electricity supply.

13.4 APPLIANCE OPERATION

Turn off the gas and electricity supplies to the appliance.
Loosen the burner pressure test point screw on the gas valve and
connect a pressure gauge. See Fig. 28.
Undo the two screws and hinge down the facia to gain access to the
mode switch. Refer to Fig. 12.

Domestic Hot Water.

Set the gas valve mode switch, at the rear of the facia, to the maximum
position. Refer to Fig. 26.
Turn on the gas and electricity supplies.
Set the CH temperature control knob fully anti-clockwise to
and the DHW temperature to MAX.
Open a hot water tap.
A continuous ignition spark will occur until the burner is alight and

Fig. 27. Pressure relief valve.

Turn knob
anti-clockwise
to test

Pressure
relief
valve

Fig. 28. Gas Valve

Max

2mm

Allen key

Min

3mm

Allen key

Gas valve
sealing
cap

Burner
pressure
test point