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Slowly reduce
the
domestic hot
water flow rate so that
the
gas
pressure reduces and
settles.
Does
the
domestic hot water temperature
stabilise at 55·60°C?
YES
Funher reduce the domestic hot
water
flow
rate so
that
the
appliance shuts down as the
domestic
hot
water
temperature
rises
above
the
set
level.
Does
the
YES
Does
the
DC
voltage
across
the
Modureg terminals decrease
as
the
flow rate reduces?
The overheat thermostat has
activated.
Allow the overheat
thermostat and repeat this test
Does
the
DEMAND
Indicator
light
go out
immediately?
YES
STAR:
Of
PUMP 0\'f RRU'J
~t
s;
With
no central
heating or domestiC
hot
water
demand
and
with
primary water above
60°(
1
apprcx.),
does the pump
operate?
YES
When
the primary temperature
drops
below
60°(
lapprox.).
does
the
pump
stop'
YES
[
Does
the burner
shut down
if
the
Gas·toWater
heat exchanger water
exceeds 100°C
Is
the
STANDBY
indicator
Ught
illuminated?
YES
Replace the pump overrun
thermostat.
Replace the system overheat
thermostat.
32
Remove the domestic hot
water
Molex plug
from terminal
X2.
Is
there
a
resistance
of
1.5 to 25
kohms
across
the red pins?
YES
Replace the flow
switch.
Refer to
section
STANDBY
lndicltDr
does not
Dluminlte.
Replace the pump overrun
thermostat
Replace the
domestic
hot water
sensor.
Replace the main driver
board.
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