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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
tightness 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 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/RESET POSITION
When the selector switch is in the OFF/RESET position, the
following functions are active.
Active functions
:
•
frost-protection system
•
pump & actuator anti-block.
7.2.2 ON-BOARD FUNCTIONS
•
CO FUNCTION:
the CO function when activated, will allow
the appliance to run a t CH maximum, DHW maximum or
minimum output 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 thermistor 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-
seconds.
•
SARA function:
the SARA function permits the boiler (when
the set-point is within the SARA range) to automatically
adjust (raise) the heating flow outlet temperature should the
room thermostat contacts remain closed for more that 20-
minutes.
7.2.3 HEATING MODE
With all controls calling for heat, the pump and fan will run.
When the fan runs it proves the air pressure switch. The air
pressure switch delivers current to the PCB and enables an
ignition sequence to begin. The ignition sequence begins with
the energising of the gas valve and a simultaneous sparking
at the spar k/sense electrode. This will continue for
approximately 10 seconds or until successful ignition has been
established. (If no ignition has been established within the ten
seconds, the ignition attempt will be terminated and the
appliance will go to lockout).
The appliance monitors the setting of the heating
potentiometer against the temperature of the primary thermistor,
and increases or decreases current to the modulating coil,
this in turn adjusts the burner pressure, thus enabling the
temperature to be maintained to within a few degrees (see
section 5.10). When the temperature of the primary thermistor
exceeds the setting of the heating potentiometer, ignition will
be terminated and the appliance will anti-cycle for three
minutes (timer delay). When a new ignition sequence begins
the output of the appliance is set at minimum for two minutes.
NOTE
Any demand for hot water has the priority.
If there is a demand for hot water whilst the appliance is anti-
cycling, the timing will be cancelled once the demand for hot
water has been satisfied.
7.2.4 HOT WATER MODE
Opening a hot water outlet and enabling a flow rate of 2 litres
or more, causes the domestic water flow switch to activate.
Activation of the domestic hot water flow switch allows the fan
to run. When the fan is running it proves (switches) the air
pressure switch. The air pressure switch delivers current to
the PCB and enables an ignition sequence to begin. The
ignition sequence begins with the energising of the gas valve
and a simultaneous
sparking at the spark/sense electrode.
This will continue for aproximately 10 seconds or until
successful ignition has been established. (If no ignition has
been established within the ten seconds, the ignition attempt
will be terminated and the appliance will go to lockout). When
ignition has been established, the appliance will quickly
achieve and maintain the desired hot water temperature (see
5.13). The appliance monitors the setting of the hot water
potentiometer against the temperature of the secondary
thermistor, and increases or decreases current to the
modulating coil, this in turn adjusts the burner pressure, thus
enabling the temperature to be maintained to within a few
degrees. When the temperature of the secondary thermistor
exceeds the setting of the hot water potentiometer, ignition
will be terminated until the temperature drops.
NOTE
The primary thermistor will overide the secondary thermistor if
the temperature of the primary thermistor exceeds 80 ºC.
When the mode selector switch is set to heating and hot water,
the pump will over-run for 30 seconds after any demand for
heating or water has been satisfied.
When the mode selector switch is set to hot water only, the fan
will over-run for one minute if the temperature of the primary
thermistor exceeds 55 ºC.
ATTENTION
Gas type and appliance output
must be set
according to the
specific appliance specification. Vokèra accepts no
responsibility if the gas type is not correctly adjusted according
to the respective appliance specification as detailed on the
appliance data badge.
SECTION 7 - CHECKS, ADJUSTMENTS AND FAULT FINDING
7.3 ADJUSTMENTS
The boiler has already been adjusted by the manufacturer.
If it is necessary to adjust it again, for example after
extraordinary maintenance, after replacement of gas valve
or after gas conversion, carry out the following procedure.
The maximum output adjustment must be carried out in
the sequence indicated exclusively by qualified personnel.
- remove the shell unscrewing the fixing screws A
- unscrew by two turns the screw of the pressure test point
downstream the gas valve and connecting the pressure
gauge
- disconnect the compensation inlet of the air distribution
box.
7.3.1 Maximum power and minimum domestic hot water
adjustment
- Fully open the hot water tap
- on the control panel:
- set the mode selector to (summer)
- turn the domestic hot water temperature selector to its
maximum
- power the boiler setting the system main switch to ON
- check that the pressure on the pressure gauge is stable; or
with a multimeter in series to the modulator, make sure that
the modulator supplies the maximum available current (120
