FAULT FINDING AND DIAGNOSIS
6 720 803 800 (2012/11)
56
7.3
PREHEAT AND DHW FUNCTION
Fig. 124 PreHeat and DHW function
W
ait
until
temperature
is below set value
IG
N
ITI
O
N
SE
QU
E
NCE
(see detail)
NO
YE
S
MAI
N
S
PO
WE
R
SUP
P
LY
ON
T
ap open
(recognised
by flow
turbine)
Diverter valve
in D
H
W
position (up)
P
u
mp O
N
.
BL
UE
LI
G
H
T
ON
BURNER
L
IT?
F
an to
start
speed.
Stop spark
and gas.
W
ait
30 seconds
4th
attempt?
LO
C
K
O
U
T
F
an
modulation
to ac
hieve
set
temperature
(4
0-6
0
°C
)
DHW
DE
MAN
D
END
Gas valve
OFF
P
u
mp overrun
10 seconds
Fan overrun
30 seconds
Over temperature
shut-down if water
temperature exceeds
a predefined limit
for primary or outlet.
Gas valve O
F
F
.
Fan overrun
30 seconds
Spark
ignition
and gas
4 seconds
NO
YE
S
PREHEAT
displayed *
AN
D
20 minutes
since last pre-
heat demand
AN
D
temperature
falls below
set point.
P
R
E
H
EA
T
DE
MAN
D
D
O
M
E
STIC
HO
T
WA
T
E
R
DE
MAN
D
(priority over
CH demands)
F
L
AM
E
SYMBOL
ON
F
an
modulation
to ac
hieve
set point in
boiler primary
PRE-HEAT
DE
MAN
D
END
IG
N
IT
ION
SEQU
E
N
C
E
*Set by pressing and holding
EC
O button for 3 seconds.
If programmer is fitted this is set by
programmer (D
HW) demand.
6720803800-06.1W
o
BL
UE
LI
G
H
T
OFF
BL
UE
LI
G
H
T
OFF
BL
UE
LI
G
H
T
ON
Gas valve
OFF
P
u
mp 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.
