VOKERA Hydra Installation & Servicing Instructions Manual - page 26
24
7.1
CHECKING APPLIANCE OPERATION
When carrying out any repairs or servicing to the
appliance, the relevant commissioning and/or
set-up 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 MODE OF OPERATION
7.2.1
START-UP
When power is first supplied to the appliance it
will go through a self-purge procedure whereby
the pump, fan and motorised valve will be
momentarily energised. The boiler will then
operate in either one of the following modes:
●
DHW pre-heat
●
Central Heating
●
DHW operation
NOTE
A DHW request has priority over the other modes
of operation.
7.2.2
PRE-HEAT
When there is no demand for heating or hot water,
the boiler will periodically light to pre-heat the
domestic hot water heat exchanger to
approximately 55
°
C (measured via the cold water
inlet sensor). This ensures that the appliance is
at operating temperature when there is a request
for domestic hot water. The parameter for the
allowable temperature drop – between pre-heat
operation – can be adjusted. If the appliance
remains inactive for a period of 24 hours, the
pump and motorised valve will be energised for
a few moments to prevent these components
from seizing. Should the flow temperature sensor
fall below 7
°
C the pump will be energised. If the
flow sensor temperature falls to below 3
°
C the
burner will be lit and the appliance will operate at
the minimum output until the temperature of the
flow sensor reaches 10
°
C, whereupon the pump
will continue to run in pump over-run mode.
7.2.3
DOMESTIC HOT WATER MODE
When the appliance is at rest, the motorised val-
ve is energised to the hot water position, when a
demand for hot water is made the cold water tem-
perature sensor activates the pump and fan.
When the fan is sensed to be operating correctly,
the ignition sequence commences. The speed of
the fan and therefore the output of the boiler is
determined by the temperature of the water
sensed by the return temperature sensor,
consequently a high temperature at the return
sensor results in a lower fan speed.
SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
7.2.4
DHW TEMPERATURE ADJUSTEMENT
The temperature of the hot water outlet can be
adjusted directly as shown in section 5.7.4 or via
the operating parameters (see section 5.10). The
boiler is also fitted with a flow-rate restrictor (fig.
27) that limits the actual flow of hot water to the
taps or outlets. This is to ensure that the boiler
maintains a reasonable outlet temperature even
if the tap or outlet is fully open.
7.2.5
CENTRAL HEATING MODE
When there is a request for heat via the time clock
and/or external controls the motorised valve and
pump will go through a self-test function this is to
ensure correct operation and valve configuration.
Once the self-test function is complete, the pump
and fan will be activated via the flow temperature
sensor. When the fan is sensed to be operating
correctly, the ignition sequence commences. The
speed of the fan and therefore the output of the
boiler is determined by the temperature of the
water sensed by the flow & return temperature
sensors, 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 and return pipes 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, the burner will switch off. The built-in
anti-cycle device prevents the burner from re-
lighting for an adjustable period of time (factory
default is 92 seconds). When the temperature of
the flow sensor falls below the set-point, the
burner will re-light.
7.3
SERVICE PARAMETERS (5 – 42)
To check or adjust the service parameters, you
must first access the service mode. This mode is
only accessible in the stand-by mode.
To access the service mode:
●
press and hold the
mode
and
S
buttons
simultaneously for 2 seconds;
●
when “COdE” appears in the display, press
S
again, “C” should now be shown on the left
side of the display, with a random number on
the right side of the display;
●
using the
+
or
-
buttons, scroll until “05”
is shown in the right side of the display;
●
press
M
to store the code;
●
press
mode
to access next mode;
●
press
to exit the sevice mode.