21
7.1
CHECKING APPLIANCE OPERATION
When carrying out any repairs or servicing to the
appliance, the relevant commissioning procedure
must be undertaken to ensure the continued safe
operation of the appliance. Particular attention
should be made to ensure gas soundness, water
soundness, and the electrical integrity of the
appliance.
7.2
APPLIANCE MODES OF OPERATION
NOTE
There must be sufficient system water pressure
(min. 0.5 bar) to ensure the water pressure switch
is activated. If there is insufficient system pres-
sure the pump and fan will be prevented from
operating and the low-pressure fault indicator will
be displayed.
7.2.1
SELECTOR SWITCH IN THE STANDBY POSI-
TION
When the selector switch is in the STANDBY
position, the following functions are active.
Active functions
:
●
frost-protection system
●
pump anti-block.
7.2.2
BOILER “ON” IN COMFORT MODE
When the function switch is in the Comfort posi-
tion, the relevant status indicators (see fig. 1A) are
displayed and the appliance is active for heating
and/or hot water requests.
Active functions
:
●
frost-protection system
●
pump anti-block
●
SARA booster function.
7.2.3
BOILER “ON” IN ECONOMY MODE
When the function switch is in the Economy
position, the relevant status indicators (see fig.
1A) are displayed and the appliance is active for
heating and/or hot water requests.
Active functions
:
●
frost-protection system
●
pump anti-block
●
SARA function.
7.2.4
APPLIANCE FUNCTIONS
●
SARA:
this function will automatically raise the
outlet flow temperature when the heating tem-
perature selector is in the 55-65°C range, if the
appliance is unable to reach the room tempera-
ture set with room thermostat.
●
SARA Booster function:
this function will auto-
matically raise the flow outlet temperature if/
when the appliance is unable to reach or main-
tain the desired flow outlet temperature.
●
Frost-protection:
this function is only active
when there are no requests for heating or HW.
Should the temperature of the primary thermis-
tor drop below 7°C, the valve actuator will mo-
tor to the heating position. Should the tempera-
ture of the primary thermistor exceed 10°C dur-
ing this period, the cycle will be aborted. If the
SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
temperature drops below 4°C, the boiler will op-
erate on minimum power until the temperature
of the primary thermistor reaches 30°C. There-
after the pump & fan will over-run for 30-sec-
onds.
●
●
●
●
●
Pump anti-block cycle:
when there has been
no heating or HW request for 24-hours, the anti-
block cycle is activated. The pump will be
activated for a period of 1- minute. If the selector
switch is in the Comfort or Economy position,
the fan will also be active for 1- minute.
7.2.5
HEATING MODE
With the selector switch in the Comfort or Economy
position and any additional controls (time clock,
room thermostat, etc,) calling for heat, the appli-
ance will operate in the heating mode.
The pump and fan will be activated via the flow
temperature sensor. When the fan is sensed to be
operating correctly, the ignition sequence com-
mences. Ignition is sensed by the electronic
circuitry to ensure flame stability at the burner.
Once successful ignition has been achieved, the
electronic circuitry allows 75% 0f the full gas rate
through the appliance. After 15 minutes (adjust-
able, see parameter 28, cap. 7.3.1) the gas rate is
increased to maximum (100%). The speed of the
fan and therefore the output of the boiler is deter-
mined by the temperature of the water sensed by
the flow temperature sensor, consequently a high
temperature at the flow sensor results in a lower
fan speed. As the water temperature increases,
the temperature sensors - located on the flow pipe
of the boiler - reduce the fan speed via the
electronic circuitry. Depending on the load, either
the water temperature will continue to rise until the
set point is achieved or the water temperature will
fall whereby fan speed will increase relative to the
output required. When the boiler has reached the
set point, the burner will switch off. The built-in
anti-cycle device prevents the burner from re-
lighting for an adjustable period of time (factory
default is 5 minutes). When the temperature of the
flow sensor falls below the setpoint,the burner will
re-light.
NOTE
If the spark/sensing electrode does not sense
ignition the appliance will re-attempt ignition a
further 4-times then go to lockout.
When the set-point has been reached (the position
of the heating temperature selector) as measured
at the primary thermistor, the appliance will begin
the modulation phase whereby the fan and gas
valve will continuously modulate to maintain the
set-point.
If the temperature continues to rise and exceeds
the set-point by 6°C, the burner will shut down. A
new ignition sequence will be enabled when the 5-
minute anti-cycle has been performed and the
temperature at the primary thermistor has dropped
6°C below the set-point.