Fer FALCON II Installation, Servicing & User Instructions page 33

8.04 Temperature sensors (thermistors)
Identical, but individual, negative temperature co-efficient (NTC) thermistors are fitted in the C.H. and D.H.W. outlets
from the heat exchanger. As the water temperature increases the resistance in the thermistor decreases. This causes the
PCB to reduce the voltage to the modureg, in turn reducing the burner pressure. The wiring for each thermistor is colour
coded red for C.H. and blue for D.H.W. The sensors are fitted in wet pockets.
8.05 Limit thermostats
Two surface mounted auto reset bi-metal thermostats are located on the heat exchanger secured by spring
clips. Heat sink compound is used.
8.06 Ignition PCB
Located to the right hand side of the electrical control compartment accessed by lowering the facia then
removing the rear cover.
8.07 Main printed circuit board
Secured by three screws, the PCB is situated inside the control compartment. The transformer for low voltage AC is
attached to the PCB as is the DC rectifier. Potentiometers control C.H. output and maximum D.H.W. temperature, both
are adjustable by the controls on the facia and because the boiler features automatic range rating no adjustments need
to be made. Electro mechanical relays control pump operation and put switched live to the ignition PCB (demand relay),
they have transparent plastic covers so that their contacts can be seen moving.
8.08 Air pressure switch
Operating at 230 V AC and situated next to the fan. Different coloured tubes connect the switch to the fan. It is a make
on pressure switch and only uses two terminals, the middle terminal is not used.
8.09 Short spares list
KEY NO. DESCRIPTION
(from fig 2 )
14 Safety Valve
16 Fan
34 Central Heating Flow Temperature Sensor
39 Cold water flow limiter
42 Domestic Hot Water Flow Temperature
Sensor
43 Air Pressure Switch
44 Honeywell Gas Valve
49 Overheat Safety Thermostat 100°C
50 High Limit Thermostat 88°C
81 Ignition Electrode °/N fixing Bracket
82 Flame Sensing Electrode
136 Flow Meter
Main PCB MF03
27 Heat Exchanger
FALCON II
PART NO. G.C. NO.
800130 386-816
800480 E23-851
800320 E23-839
800320 E23-839
800150 E23-840
800266 E23-768
801270 386-815
800160 386-577
806460
801438 E23-855
803430 E03-340
802180 E23-919
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