44
NOTE:
please refer to section 4, section 4.1 and use the ap-
propriate PPE when carrying out any of the actions or proce-
dures contained within this section.
8.1 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.
8.2 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.
8.2.1 OFF
When the appliance has been set to OFF via the REC10CH
UI, the following functions will remain active:
• frost-protection system
• pump & actuator anti-block.
8.2.2 ON-BOARD FUNCTIONS
•
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-seconds.
•
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.
•
DHW PRE-HEAT FUNCTION:
when the DHW pre-heat
function is enabled, the appliance will light periodically to
maintain the temperature of the DHW heat exchanger. When
the DHW thermistor and the primary thermistor fall below 35°C
and 55°C respectively, the boiler will fire on m25%
power until the primary thermistor exceeds 55°C. Thereafter
the pump will over-run for a period of 30-seconds.
8.2.3 HEATING MODE
When a ‘heating’ request is generated via the connected
external control/s and/or the REC10CH UI, 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
commences. 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
8. SECTION - CHECKS, ADJUSTMENTS AND FAULT FINDING
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 burner ignition is not detected at the first attempt, the
appliance will repeat the ignition sequence another two times
(3-times in total) before going to lockout. When the set-point
has been reached 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.
8.2.4 DHW MODE
The appliance will operate in the hot water mode whenever
a DHW outlet is opened. The appliance flowmeter will detect
water movement (min 2L/pm) and signal a hot water request
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
satisfied, the appliance pump and fan may continue to circulate
to dissipate any residual heat within the appliance.
ATTENTION
Gas type and appliance outputs are factory set by default, at
the values declared in the specification data in section 2.
Vokera cannot accept any responsibility for any damage or
malfunction that has been caused as a result of tampering
or incorrect set up of this appliance during installation or
commissioning.
8.3 CHECKING THE EXPANSION VESSEL
Carry out the component removal procedure. You must ensure
that the boiler is completely drained of water. Using a suitable
pressure gauge, remove dust cap on expansion vessel and
check the charge pressure. The correct charge pressure should
be 1.0 bar ± 0.1 bar. If the charge pressure is less, use a suitable
pump to increase the charge.
NOTE:
you must ensure the drain valve is in the open position
whilst re-charging takes place. Replace the dust cap and carry
out the relevant commissioning procedure (section 6).
8.4 EXTERNAL FAULTS
Before carrying out any faultfinding or component replacement,
ensure the fault is not attributable to any aspect of the installation.
8.4.1 INSTALLATION FAULTS
Symptom
Possible cause
No ignition
Check wiring/check electrical
supply/check gas supply
No hot water
Check pipe-work
No heating
Check external controls
Fault
Possible cause
Fault code
Check gas supply, check flue
system
