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24. Pressure
Gauge.
See
Fig 31
Check that the electricity supply
to
the appliance is turned
off.
Drain the appliance as described
in
Section 1
5.3(a).
Lower the
facia panel as described
in
Section 14.3(c).
Remove the two screws securing the gauge
to
the
facia
panel.
Hang the control box assembly
in
the servicing position as
described
in
Section 14.3(d).
Disconnect the capillary at
the
pressure relief valve and remove
the
gauge.
Fit
the replacement
gauge
in the reverse
order ensuring
the
fibre
washer
is in
place.
Open the valves and
fill
and
re-pressurise
the system as described
in
Section
12.2.
25.
Operating
Switch.
See
Fig 31
Check
that the
electricity supply to
the
appliance
is
turned
off.
Lower
the
facia panel as described
in
Section
14.3(c).
Remove
the
leads from the
rear
of the switch making note of
their
positions.
Squeeze
together
the two plastic retaining lugs
to
remove the
switch
from
the
facia.
Snap
in the replacement switch and reconnect
the
leads.
Refer
to the
wiring
diagram, Fig.
7
26.
Temperature Control
Potentiometer.
See Fig 31
Check
that
the electricity supply to
the
appliance
is turned
off.
Lower the facia as described
in
Section
14.3(c).
Pull
the
knob off
the
spindle.
Unscrew the locknut and remove
the
potentiometer from the facia panel. Remove the Molex plug
from terminal
X1 on
the driver
board.
Fit the
replacement potentiometer
in the
reverse order.
Fig.
31
.
Facia
(rear view in lowered
position).
0
t======-f
28.
Domestic Hot
Water Overheat
Thermostat
See
Fig.
26.
Check
that the electridty 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 thermostat. Loosen
the
two M3 screws holding the thermostat to the fitting and remove
the thermostat.
Fit the replacement thermostat
in
the reverse order ensuring a
layer of heat sink compound is between the faces
.
Refit the
leads.
27.
Driver
Board.
See
Fig
7
Check that the electricity supply
to the
appliance
is
turned
off.
Lower the facia panel as described
in
Section 14.3(c)
Carefully pull off all the Molex connectors
from
the
board.
Dis·
connect the room and frost thermostat connections
(if
fitted)
from terminal
X4.
Remove
the
Operating Switch
(or
program·
mer) plug from terminal
X1
0.
Disconnect the mains supply
leads at terminal
X7.
Release the plastic catch
in
each
corner
of
the driver board and pull forward off
the control
panel.
Fit the replacement board
in the reverse
order ensuring
it is
pushed
firmly
onto
the
four posts and clicks
into
place.
Refit
the facia
panel and
hang
the
control
box assembly
in the
servicing position as described
in
Section
14.3
(d).
Set the central heating operating pressure to 14.4 mb (5.8
in wg)
by adjusting
(anti-clockwise to increase
the pressure
and
clock·
wise to decrease the pressure)
the
central heating potentiometer
accessed through an opening
in
the rear of the control
box.
This
must be done with
the
boiler operating
in the central
heating
mode.
The adjustment
is
made using a thin flat-bladed screwdriver.
0
Temperature control potentiometer
1==;::;:==
\
Operating Switch
\\\1
/_0"\
riJ)Cj
Indicator
l
i
g hts~
._ _ ______.
\
0
~/----4
~~------------------0~~~----------1----~
-I
Pressure gauge
fixing
screws
(21
lo
Operating Switch plate
(or
programmer) fixing screws (41
24
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