FAULT FINDING AND DIAGNOSIS
6 720 803 800 (2012/11)56
7.3 PREHEAT AND DHW FUNCTION
Fig. 124 PreHeat and DHW function
Wait until
temperature
is below set value
IGNITION
SEQUENCE
(see detail)
NO
YES
MAINS
POWER
SUPPLY
ON
Tap open
(recognised
by flow
turbine)
Diverter valve
in DHW
position (up)
Pump ON.
BLUE
LIGHT
ON
BURNER
LIT?
Fan to
start
speed.
Stop spark
and gas.
Wait
30 seconds
4th
attempt?
LOCKOUT
Fan
modulation
to achieve
set
temperature
(40-60°C)
DHW
DEMAND
END
Gas valve
OFF
Pump overrun
10 seconds
Fan overrun
30 seconds
Over temperature
shut-down if water
temperature exceeds
a predefined limit
for primary or outlet.
Gas valve OFF.
Fan overrun
30 seconds
Spark
ignition
and gas
4 seconds
NO
YES
PREHEAT
displayed *
AND
20 minutes
since last pre-
heat demand
AND
temperature
falls below
set point.
PREHEAT
DEMAND
DOMESTIC
HOT
WATER
DEMAND
(priority over
CH demands)
FLAME
SYMBOL
ON
Fan
modulation
to achieve
set point in
boiler primary
PRE-HEAT
DEMAND
END
IGNITION SEQUENCE
*Set by pressing and holding
ECO button for 3 seconds.
If programmer is fitted this is set by
programmer (DHW) demand.
6720803800-06.1Wo
BLUE
LIGHT
OFF
BLUE
LIGHT
OFF
BLUE
LIGHT
ON
Gas valve
OFF
Pump overrun
10 seconds
Fan overrun
30 seconds
If no DHW demand, check
flow turbine connection is
made, refer to section 7.1
Also ensure that pipes are
not crossed.
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