5
Domestic Hot Water Mode
To be able to supply hot water, the DHW
mode should be ON. Press on key
28
, the green indicator
32 will light.
If there is no water demand, the display
will show the following graphic
if
the TSS® is cold, the burner
will light immediately. In case of draw off,
a square made of 4 digits will move
clockwise on the display
.
Keys
30
and
31
allow the adjust-
ment of the temperature required for
D.H.W., flow. During the temperature
setting operation, the display will flash.
When a tap or a shower is turned on, the
flow of mains water, above 2 litres per
min., will activate the DHW flow switch
20 or if the TSS® thermistor is calling for
heat and allow the 3 way valve
17 to
move to the DHW position. The pump
can now circulate primary water heated
by the main exchanger through the sec-
ondary heat exchanger and TSS® coil.
The primary flow switch checks that this
flow rate is over 4lt./min. before allowing
the lighting sequence to begin.
The fan on the gas valve assembly starts
and when the lighting speed is reached
(detected by a hall effect sensor) the 2
safety solenoids 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 led
34
will light and the regulation system will
be able to adjust the gas rate regarding
the heat load. If the TSS® thermistor is
calling for heat, the burner will stay in
minimum output. If a flame is not detect-
ed, after 10 seconds, the security sole-
noids close together and shut off the
gas. The red lockout indicator led
38 will
light. Press the reset button to re-light
the burner.
For flow rates of less than 2 l/min, the
domestic hot water temperature is con-
trolled by TSS® thermistor
23 and heat-
ing thermistor
21. For flow rates over 2
l/min , the domestic hot water tempera-
ture is controlled by hot water control
thermistor
22 and the central heating
control thermistor
21. This system antici-
pates the changes of temperature in the
secondary heat exchanger and ensures
accurate temperature regulation.
When the tap is closed the burner may
stay alight until the TSS® cylinder is up
to temperature. Then the burner is extin-
guished and the pump stops. The boiler
will now stay in the hot water mode for 3
minutes to maintain temperature to
ensure a fast response in the event of a
subsequent hot water demand.
Priority will be given to a demand for hot
water or re-heating of the TSS® cylinder.
This will interrupt the central heating for
the duration of hot water supply.
Central Heating Mode
To be able to supply heating, the mode
should be switched ON. Press key
29
, the green indicator
33 will light, and
the display will show the Heating Flow
temperature.
Keys
34
and
35
allow the adjust-
ment of the temperature required for the
Central Heating system regarding the
weather conditions. During the setting
operation, the display will flash.
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
the primary flow rate is over 4 lt./min.,
the central heating flow switch operates,
allowing the ignition sequence to begin.
The fan on the gas valve assembly starts
and when the lighting speed is reached
(detected by a hall effect sensor) the 2
safety solenoids 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 LED
37
will light and the regulation system will
be able to adjust the gas rate regarding
the heat load. If a flame is not detected,
after 10 seconds, the security solenoids
close together and shut off the gas. The
red lockout indicator LED
38 will light.
Press the reset button to re-light the
burner.
The Central Heating flow temperature is
controlled by the Central Heating control
thermistor
21. The boiler has been
designed to minimise cycling and will not
attempt to re-light for at least 3 min. after
the boiler thermostat has been satisfied.
When the room thermostat is satisfied ,
the burner will switch off and the pump
will remain running for a further 3 min-
utes before it too stops.
Note: It is possible to override the 3
minute delay by pressing the Reset key
39.
