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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 tightness, water tight-
ness and the electrical integrity of the appliance.
7.2 APPLIANCE MODES OF OPERATION
NOTE
There must be suffi cient system water pressure (min. 0.5 bar)
to ensure the water pressure switch is activated. If there is in-
suffi cient system pressure the pump and fan will be prevented
from operating and the low-pressure fault code will be indicated.
7.2.1 SELECTOR SWITCH IN THE OFF POSITION
When the selector switch is in the OFF position, the following
functions are active.
Active functions
:
frost-protection system
pump anti-block.
7.2.2 ON-BOARD FUNCTIONS
CO FUNCTION:
the CO function when activated, will allow
the appliance to run at CH maximum, whilst a combustion
analysis check or a mechanical gas valve calibration is being
carried out. Whilst the CO function is active, all other functions
are disabled (minimum power operating period, anti-cycle,
set-point, etc). Once enabled, the CO function will remain
active for a 15-minute period, or until the function is manually
deactivated.
FROST-PROTECTION:
this function is only active when there
are no requests for heating or HW. If the temperature drops
below 5°C, the boiler will operate on minimum power until
the temperature of the thermistors reaches 35°C . Thereafter
the pump & fan will over-run for 30-seconds.
ANTI-CYCLE FUNCTION:
the anti-cycle function ensures the
burner remains switched off for at least 3-minutes after the
set-point hysterisis (set-point + 5-deg) for CH heat request.
PUMP ANTI-BLOCK FUNCTION:
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 30-sec-
onds.
SARA function:
the SARA function permits the boiler (when
the set-point is within the SARA range) to automatically adjust
(raise) the heating fl ow outlet temperature should the room
thermostat contacts remain closed for more that 20-minutes.
7.2.3 HEATING MODE
With the selector switch in the heating & hot water position
and any additional controls (time clock, programmer, room
thermostat, etc.) calling for heat, the appliance will operate
in the heating mode. The pump and fan will be activated via
the fl ow temperature sensor. When the fan is sensed to be
operating correctly (tacho signal), the ignition sequence com-
mences. Ignition is sensed by the electronic circuit to ensure
fl ame stability at the burner. Once successful ignition has been
achieved, the electronic circuitry increases the gas rate to 75%
for a period of 15 minutes.
The speed of the fan and therefore the output of the boiler is
determined by the temperature of the water sensed by the
fl ow temperature sensor, consequently a high temperature at
the fl ow sensor results in a lower fan speed. As the water tem-
perature increases, the temperature sensors – located on the
fl ow 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
(+ hysterisis), the burner will switch off. The built-in anti-cycle
device prevents the burner from re-lighting for approximately
3-minutes. When the temperature of the fl ow sensor falls below
the set point (- hysterisis), the burner will re-light.
NOTE
If the spark/sensing electrode does not sense ignition the appli-
ance 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 5°C (hysterisis), the burner will shut down. A new ignition
sequence will be enabled when the 3- minute anti-cycle has
been performed and the temperature at the primary thermistor
has dropped 5°C (hysterisis) below the set-point.
ATTENTION
Gas type and appliance output
must be set
according to the
specifi c appliance specifi cation. Vokèra accepts no responsi-
bility if the gas type is not correctly adjusted according to the
respective appliance specifi cation as detailed on the appliance
data badge.
SECTION 7 - CHECKS, ADJUSTMENTS AND FAULT FINDING
Summary of Contents for Mynute i20
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