4
2) If the room thermostat (if fitted), the
boiler temperature control
and the
clock (if fitted) are all calling for heat, the
orange "burner on" indicator
21 will
light and the heating will be on.
When there is a need for hot water while
the heating is on, it is only necessary to
turn on a hot tap. The heating will be
interrupted momentarily while the hot
water is being delivered. The boiler will
switch back automatically to heating
when the tap is turned off.
Note: if the boiler has been turned off for
some time the first attempt to light it may
result in a lockout
. If this happens
press the reset button 23 and the boiler
will light.
To Turn Boiler Off Completely
1) Turn the selector switch 15 to the off
position O.
2) Turn the gas tap 3 Fig. 2 OFF.
Domestic Hot Water Mode
In order to supply hot water, the main
switch 15 Fig. 4 must be in ON position I
This will be confirmed by the green indica-
tor light
20 Fig. 4. Turn the selector
switch 16 clock wise to establish the green
DHW indicator 38 Fig. 4.
When a tap or shower is turned on, the
flow of mains water, above 2 litres per
min., will activate the 3 way valve 41 Fig. 5
to move to the DHW position. The pump
will now circulate primary water heated by
the main heat exchanger through the sec-
ondary heat exchanger.
The safety solenoid 30 and 31 Fig. 5 open
together to allow gas to the burner. The
ignition sequence begins and a continu-
ous high speed spark ignites the gas. As
soon as a flame is detected the orange
indicator bulb
21 Fig. 4 will light and the
second stage solenoid 32 Fig. 5 opens to
allow the full gas rate. If a flame is not
detected, after 8 seconds, the security
solenoids close and shut off the gas. The
red lockout indicator bulb
22 Fig. 4 will
show. The domestic hot water tempera-
ture is controlled by the hot water control
thermistor 10 Fig. 5 and the central heat-
ing control thermistor 9 Fig. 5. This sys-
tem anticipates the changes of
temperature in the secondary heat
exchanger and ensures accurate temper-
ature regulation.
When the tap is closed the burner is extin-
guished and the pump stops.
Priority will be given to a demand for hot
water. This will interrupt the central heat-
ing for the duration of hot water delivery.
Central Heating Mode
To be able to supply heating, the main
switch 15 Fig. 4 must be in I position. This
will be confirmed by the green indicator
light
20 Fig. 4. Turn the selector
switch 17 clock wise to establish the
green heating indicator 37 Fig. 4.
When there is a demand for heating
(either from the room thermostat or the
clock) and the boiler temperature control
is calling for heat. The pump starts allow-
ing the ignition sequence to begin.
The safety solenoid 30 and 31 Fig. 5
open together to allow gas to the burner.
The ignition sequence begins and a con-
tinuous high speed spark ignites the gas.
As soon as a flame is detected the
orange indicator bulb
21 Fig. 4 will
light. After 45 seconds the second stage
solenoid 32 Fig. 5 opens to allow the full
gas rate. If a flame is not detected, after
8 seconds, the security solenoids close
and shut off the gas. The red lockout
indicator bulb
22 Fig. 4 will show.
The central heating flow temperature is
controlled by the central heating control
thermistor 9 Fig. 5. The boiler has been
designed to minimise cycling and will not
attempt to relight for 3 minutes after the
boiler thermostat has been satisfied (it is
possible to reduce the time to 30 s if nec-
essary). When the room thermostat is
satisfied the burner will switch off and
the pump will remain running for a fur-
ther 4 minutes before it stops.
NB : it is possible to override the 3 minute
delay by putting off and on the central
heating selector switch 17.
19 17 15 13 11 9 7 5 3 1
20 18 16 14 12 10 8 6 4 2
08 07 06 05 04 02 01
A
B
A
B
NC
C
NO
01
02
09
2
P
1
06
05
04
07
08
09
910
7
68
5
2
1
4
3
14
11
20
21
21
19
Room
thermostat
Main supply
230 V 50Hz
Pump
Spark Generator
Spark
electrodes
Fan
Pressure switch
Safety thermostat
1 green
green
2
H.W.
Thermistor
3 purple
4
Heating
Thermistor
purple
grey
grey
D.H.W. microswitch
5
8
blue
blue
6
7
Security solenoid
valve
Security solenoid
valve
Solenoid valve
black
black
9
10
brown
brown
11
14
01
02
04
05
07
08
06
09
brown
blue
mass
white
orange
black
brown
brown
green /
yellow
brown
white
mass
Sensing electrode
15
16
black
black
19
20
21
green /
yellow
15
16
Pressure switch
security
mass
c
a
b
le
c
a
b
le
A
B
0.8b
WIRING
DIAGRAM
