23
7.3 CHECKING THE CO
2
AND ADJUSTING THE
GAS VALVE
THE GAS VALVE MUST BE SET-UP OR ADJUSTED WITH
THE AID OF A PROPERLY CALIBRATED FLUE GAS ANA
-
LYSER.
Isolate the appliance from the electrical supply and remove the
appliance casing as described in 4.7.1. Restore the electrical
supply to the boiler and switch the boiler to the OFF mode.
Have access to the printed circuit board, locate and open the
closing plug on the dash board (L2), locate and press the CO
button (see fig. 36 pos. SW1). Press the button the number of
times according the function requirement as par 7.3.1.
Set the flue gas analyser to read CO2, allow the burner to
stabilise and insert the probe into the flue analysis test point
(Y1-Z1 fig. 33). The appliance will operate in CO2 mode for
approximately 15 minutes.
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 sufficient system water pressure (min. 0.5 bar)
to ensure the water pressure switch is activated. If there is in-
sufficient 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 at 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 thermistors reaches 35°C for CH
and 55°C for DHW. 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.
•
ACTUATOR ANTI-BLOCK FUNCTION:
when there has been
no heating or HW request for 24-hours, the anti-block cycle
is activated. The divertor valve actuator will motor briefly to
the heating position, and then back to the DHW position. The
pump will run briefly.
•
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 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 flow 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
flame 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 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 (+ 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 flow 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.
7.2.4 DHW MODE
With the selector switch in either the hot water only or heating
& hot water position, the appliance will operate in the hot water
mode whenever a DHW outlet is opened. A flow rate exceeding
2-litres per minute will activate the DHW flow switch whereupon
the pump and fan will be activated via the flow temperature
sensor. When the fan is sensed to be operating correctly (tacho
signal), the ignition sequence commences. Ignition is sensed
by the electronic circuitry to ensure flame stability at the burner.
Once successful ignition has been achieved, the electronic
circuit allows the gas rate to achieve the modulation value.
NOTE
When the request for heating and/or hot water has been satis-
fied, the appliance pump and fan may continue to circulate to
dissipate any residual heat within the appliance.
ATTENTION
Gas type and appliance output
must be set
according to the
specific appliance specification. Vokèra accepts no responsi
-
bility 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
L2
Fig. 36
SW1
use the supplied
screwdriver to push the
CO botton (SW1)
