Checks, Adjustments And Fault Finding; Checking Appliance Operation; Appliance Modes Of Operation; Heating Mode - Riello Vokera VISION PLUS 20 S User Instructions

8

CHECKS, ADJUSTMENTS AND FAULT FINDING

N OTE
Please refer to 3 - 3E and use the appropriate PPE when
carrying out any of the actions or procedures 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 in-
sufficient system pressure the pump and fan will be prevented
from operating and the low-pressure fault code will be indicated.
8.2.1 MODE SELECTION IN THE OFF/RESET POSITION
When the mode selection is in the OFF/RESET position, the
following functions are active.
Active functions:
• frost-protection system
• pump anti-block.
8.2.2 ON-BOARD FUNCTIONS
• CO FUNCTION: the CO function when activated, will allow
the appliance to run at CH maximum, 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. 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.
8.3

HEATING MODE

With the mode selection 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 commences. Igni-
tion 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.
36
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.
8.4 CHECKING THE CO
THE GAS VALVE
THE GAS VALVE MUST BE SET-UP OR ADJUSTED WITH THE
AID OF A PROPERLY CALIBRATED FLUE GAS ANALYSER.
Isolate the appliance from the electrical supply and remove the
appliance casing as described in 4.7.
Set the flue gas analyser to read CO2 and insert the probe into
the flue analysis test point.
8.4.1 COMBUSTION CHECK
To carry out the combustion analysis, proceed as follows:
ƒ set the boiler to the OFF status by pressing button 1
ƒ Remove the screw and the cover on the air distribution box
A-B
( ).
ƒ Insert the analysis probe adapter (
documentation envelope, into the hole for the combustion
analysis.
ƒ Insert the flue gases analysis pro be into the adaptor.
A
B
AND ADJUSTING
2
D
) located in the
D
Fig. 38