VOKERA RAIN 24 Installation And Servicing Instructions - page 16
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24/28/bi
24/28/bi
24/28/bi
24/28/bi
24/28/bi
7.1
CHECKING APPLIANCE OPERATION
When carrying out any repairs or servicing to the
appliance, the relevant commissioning proce-
dure must be undertaken to ensure the continued
safe operation of the appliance. Particular atten-
tion should be made to ensure gas soundness,
water soundness, and the electrical integrity of
the appliance.
7.2
APPLIANCE MODE 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.
7.2.1
SELECTOR SWITCH IN THE ‘OFF’ POSITION
When the selector switch is in the OFF position,
the Green LED status indicator will flash every 6-
seconds to confirm the appliance is in standby
mode. The appliance will not respond to any
heating requests.
Active functions:
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●
●
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frost-protection system
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pump anti-block
●
fan over-run.
7.2.2
SELECTOR SWITCH IN THE ‘ON’ POSITION
When the selector switch is in the ON position,
the Green LED is illuminated:
●
flashing every 6-seconds if no Heat and/or hot
water request is active
●
constant during a heat and/or hot water re-
quest.
Active functions:
●
●
●
●
●
frost-protection system
●
●
●
●
●
pump anti-block
●
●
●
●
●
fan/pump over-run.
7.2.3
APPLIANCE FUNCTIONS
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Frost-protection:
this function is only active
when there are no requests for heating and/or
hot water. When the temperature of the primary
thermistor drops below 5 °C, the boiler will
operate on minimum power until the tempera-
ture of the primary thermistor reaches 35 °C.
Thereafter the pump will over-run for 30-sec-
onds.
●
●
●
●
●
Anti-block cycle:
when there has been no
heating or hot water request for 19-hours, the
anti-block cycle is activated and the pump will
be activated for a period of 30-seconds.
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●
●
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Fan over-run:
should the temperature of the
NTC thermistor exceed 78 °C after a heating or
hot water request, the pump and/or fan will run
for a period of 30-seconds.
●
●
●
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SARA function:
the SARA function permits
the boiler (when the set-point is within the
SARA range) to automatically adjust (raise) the
flow outlet temperature should the room ther-
mostat contacts remain closed for more that
20-minutes.
SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
7.2.4
HEATING MODE (fig. 12A)
With the selector switch in the ON position and
the relevant controls (time clock, room thermo-
stat, etc,) are calling for heat, the appliance will
operate and the pump and fan will be active. The
operation of the fan causes the air pressure
switch to deliver a signal voltage to the control
PCB. A slow ignition sequence is enabled,
whereby the current supplied to the gas valve
modulating coil is progressively increased from
minimum to maximum over a period of 8-sec-
onds. During this period the ignition electrode
sparks continuously even if the burner has ig-
nited. Ignition is sensed by the electronic circuitry
to ensure flame stability at the burner. Once
successful ignition has been achieved, the elec-
tronic circuitry allows 75% 0f the full gas rate
through the appliance. After 15 minutes the gas
rate is increased to maximum (100%).
NOTE
If the spark/sensing electrode does not sense
ignition the appliance will then go to lockout.
When the set-point has been reached (the posi-
tion of the heating temperature selector) as meas-
ured 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
o
C, the burner will shut down
and the boiler will perform a three-minute anti-
cycle (timer delay).
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
6 °C below the set-point.
Fig. 12A