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SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
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
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 displayed.
The 2-digit display can show several different
modes of operation:
Standby/OFF mode
Frost protection mode active
Combustion analysis mode active
Autostop function active
Normal heating request (example 60
o
C).
Normal DHW request (example 60
o
C).
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 & fan anti-block
7.2.1
ON-BOARD FUNCTIONS
•
THERMOREGULATION:
When an external
sensor is connected to the appliance, the
electronic circuitry will automatically adjust the
flow outlet temperature to suit local weather
conditions in order to maintain comfort and
efficiency. A specific operating curve that is
most suited to the system type and geographical
area can also be selected.
•
OPE:
OT+ is a communication
protocol that enables the boiler to be linked or
connected to other OT+ controls. These controls
have been designed to further increase fuel
economy by ensuring the boiler remains in the
modulation phase during any heating requests.
This reduces the amount of ON/OFF periods
and therefore increases fuel efficiency.
•
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 6°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
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).
•
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.
•
DHW PRE-HEAT FUNCTION:
When the mode
selector switch is in the DHW pre-heat position,
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
o
C and 55
o
C respectively,
the boiler will fire on m25% power until
the primary thermistor exceeds 55
o
C. Thereafter
the pump will over-run for a period of 30-seconds.
7.2.5
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 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
