
When there is a need for hot water tank
reheating while the heating is on. The
heating will be interrupted momentarily
while tank is reheated. The boiler will
switch back automatically to heating
when the tank is at temperature.
Note: If the boiler has been turned off for
some time the first attempt to light it may
result in a lockout . 22.If this happens
press the reset button 23 and the boiler
will light.
Domestic Hot Water Mode
To be able to supply hot water, the selec-
tor switch 15 must be in either on or
position. This will be confirmed
by the green indicator light 20
When the aquastat of the tank is on, it
activates the DHW flow switch 44 and
allow the 3 way valve 42 to move to the
HW position. The pump can now circu-
late primary water heated by the main
heat exchanger through the tank heat
exchanger.
The first stage solenoid 31 (blue) and
security solenoid 30 (grey) open together
to allow gas to the burner. The ignition
sequence begins and a continuous high
speed spark ignites the gas. As soon as
a flame is detected the orange indicator
bulb 21 will light and the second stage
solenoid 32 (black) opens to allow the full
gas rate. If a flame is not detected, after
8 seconds, the security solenoid closes
and shuts off the gas. The red lockout
indicator bulb 22 will light. The water
flow temperature is controlled by the
central heating control thermistor 37.
When the tank is at temperature, the
burner is extinguished and the pump
stops. The boiler will now stay in the hot
water mode for three minutes.
Priority will be given to a demand for hot
water tank reheating. This will interrupt
the central heating for the duration of hot
water tank reheating.
Central Heating Mode
To be able to supply heating, the selector
switch 15 must be on position.
This will be confirmed by the green indi-
cator light 20.
When there is a demand for heating
(either from the room thermostat or the
clock) the pump starts. If the boiler tem-
perature control is calling for heat and
primary flow rate over 4 ltr/min, the cen-
tral heating flow switch operates allowing
the ignition sequence to begin. The first
stage solenoid 31 (blue) and security
solenoid 30 (grey) open together to allow
gas to the burner. The ignition sequence
begins and a continuous high speed
spark ignites the gas. As soon as a flame
is detected the orange indicator bulb
21 will light. After 45 seconds the second
stage solenoid 32 (black) opens to allow
the full gas rate. If a flame is not detect-
ed, after 8 seconds, the security solenoid
closes and shuts off the gas. The red
lockout indicator bulb 22 will light.
The central heating flow temperature is
controlled by the central heating control
thermistor 37. The boiler has been
designed to minimise cycling and will not
attempt to relight for at least 3 minutes
after the boiler thermostat has been sat-
isfied. When the room thermostat is sat-
isfied the burner will switch off and the
pump will remain running for a further 3
minutes before it too stops.
NB
It is possible to override the 3 minute
delay by pressing the RESET button 23.
Lock out procedure
Flame disappearance :
When the ionisation electrode 28does
not detect flame presence. The orange
indicator lamp 21 extinguishes. A lighting
cycle starts. If a flame is not detected
before 8 seconds, the grey security sole-
noid 30 and the blue 1/3 solenoid 31will
close. The lock out red indicator 22
lights, the pump 35 runs and the 3 way
valve 42 stays in its position.
After a few seconds, it will become possi-
ble to reset the boiler by pressing the
reset button 23.
Overheat detection :
If an overheat is detected by the sensor
13, the grey security solenoid 30 and the
blue 1/3 31 closes, the orange indicator
lamp 21 extinguishes. The ignitor is
energised for 8 seconds and the red
lockout indicator 22 ligths. If the burner
cannot relight the boiler will go to lockout.
4
Plug for main power and Room
thermostat connection
12 3 45
1. Neutral
2. Phase
3. Room thermostat live
4. Accelerator resistor
5. Common for Accelerator and room
thermostat.
WIRING
DIAGRAM