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SECTION 9 OPERATIONAL CHECKS AND WIRING DIAGRAMS
9.1
On completion of any service/fault finding task
which has required the breaking and remaking
of electrical connections, the checks Earth
Continuity, polarity and Resistance to Earth
must be repeated.
The following flow diagrams suggest the logical
sequence of steps for fault finding.
They are not exhaustive but cover all that can
reasonably be carried out on site by the
installer.
Acquaintance with the functional sequence
will prove helpful for some, and this is included
for reference. As further help, the role of each
part is briefly described.
Also included in this section are wiring dia-
grams and schematics to assist in fault loca-
tion and servicing as described in the text.
9.2
Sequence of Functions
When following this sequence, refer to figs. 39
& 40. It is assumed that the mode selector
switch is in the
9.2.1
Rest (No demand for central heating or hot
water)
With no demand for heating or hot water the
appliance will periodically light to preheat the
domestic hot water heat exchanger. This is
done to ensure that when a demand is made
for domestic hot water the appliance is not
cold, thereby reducing the wait for hot water.
(This function can be deactivated by a service
engineer). See page 58.
Once every 19 hours the appliance will auto-
matically activate and deactivate the pump
and motorised valve (provided the electrical
supply is on to the appliance). This will help
prevent these components becoming stuck if
the appliance is not used for long periods.
The temperature indicator will always display
the temperature of the boiler unless domestic
hot water is drawn where it will indicate the
temperature of the hot water leaving the
appliance.
9.2.2
Domestic Hot Water Mode
Turning on a tap will cause the domestic hot
water flow switch to activate.
Activation of the domestic hot water flow switch
operates the motorised valve. Operation of
the motorised valve mechanically diverts the
primary water to the domestic heat exchanger
in stand-by mode the diverter valve is already
in DHW position. The pump is started simulta-
neously and with sufficient primary water
pressure the fan starts which results in a
voltage produced by the DAPS. Once this
action has been proven the gas valve will be
energised and the electrode will start to spark.
32
Supplied By www.heating spares.co Tel. 0161 620 6677
position.
If a flame is detected during the ignition at-
tempt time (8-12 seconds) the sparking will
cease, the gas valve will remain energised
and the appliance will produce hot water as
described below.
If a flame is not detected the appliance will go
to lockout (failure to detect a flame during
ignition attempt time). The gas valve will be
de-energised and the sparking will stop. (See
self diagnostic error codes)
To reset the appliance after lockout turn the
mode selector switch to the reset position for
approximately 10 seconds then back to origi-
nal position.
The temperature rise of primary water and
domestic hot water in the appliance is sensed
by thermistors on the flow tube and hot water
outlet.
An increase in temperature will in turn de-
crease the voltage to the fan. The difference in
pressure is detected by the differential
analogue pressure switch (DAPS) and alters
the voltage produced from it and transmits this
to the pcb. The pcb will in turn decrease the
voltage reaching the modulator coil causing
the gas rate to be lowered in proportion to the
fan speed. If the temperature rise is too great
the fan and gas valve will turn off completely.
Conversely a fall in temperature of the primary
and domestic hot water will increase voltage
to the fan and this in turn increases the gas
rate accordingly.
Temperature of the domestic hot water leav-
ing the appliance is shown at the temperature
indicator whenever hot water is drawn.
Constant monitoring of the temperature of the
primary and domestic hot water by the
thermistors will regulate the gas rate to main-
tain an average heat input.
NOTE: As the thermistor senses the tempera-
ture of the primary water leaving the main heat
exchanger, the amount of heat transferred
from the primary water to the dhw water de-
pends upon the temperature differential be-
tween them.
When the dhw water draw off rate drops below
the permitted minimum (2.0 l/min) the domes-
tic hot water flow switch is deactivated, and
the appliance either reverts to the 'Rest' mode
where the fan may overrun to remove residual
heat, or if there is a call for heating to the mode
described below.
Linea Plus AG
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