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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 soundness, water
soundness, and the electrical integrity of the appliance.
7.2 APPLIANCE MODES OF OPERATION
NOTE
The 2-digit display can show several different modes of
operation:
OFF mode
Frost protection mode active
Combustion analysis mode active
Autostop function active
Normal heating request (example 60
o
C).
Purge cycle mode.
SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
7.2.1 SELECTOR SWITCH IN THE OFF/STANDBY
POSITION
When the selector switch is in the OFF/STANDBY position,
the following functions are active.
Active functions
:
•
Frost-protection system
•
Pump anti-block
7.2.2 ON-BOARD FUNCTIONS
•
AUTOSTOP:
Further information on the AUTOSTOP
function, can be obtained from your local Vokera Sales
Representative.
•
CO FUNCTION:
The CO function when activated, will
allow the appliance to run at maximum and minimum
output whilst a combustion analysis check 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 primary thermistor
reaches 35°C. Thereafter the pump & fan will over-run for
five minutes.
•
ANTI-CYCLE FUNCTION:
The anti-cycle function ensures
the burner remains switched off for at least 5-minutes after
the set-point hysterisis (set-point + 2 -8 °C).
•
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.
•
PUMP DISCHARGE FUNCTION:
at the end of any
power on, the boiler makes an ON/OFF pump cycle
(about 2 minutes). Only at the end of this procedure the
boiler can satisfy any kind of CH requests.
•
PUMP CYCLE MODE:
wen power is restored to the PCB
and/or the PCB is powered for the first time, the appliance
will enter a 2-minute purge cycle whereby only the pump
will run for 15-seconds then off for 15-seconds and will
not “fire” until this period has elapsed.
7.2.3 HEATING MODE
With the selector switch in the ON position and any additional
controls (time clock, programmer, room thermostat, etc,)
calling for heat, the appliance will operate in the heating
mode. The external 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 circuitry increases the
gas rate to 75% of the MAX Heating (set by the corresponding
HTG trimmer) 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 tempera-
ture sensor, consequently a high temperature at the flow
sensor results in a lower fan speed. As the water tempe-
rature 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 5-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
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 2°C (hysterisis), 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 8°C (hysterisis) below the
set-point.
NOTES
When the request for heating and/or hot water has been
satisfied, the appliance pump and fan may continue to
circulate to dissipate any residual heat within the appliance.
OR
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