Ferroli F24 Installation, Servicing And User Instructions Manual page 38

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 Main printed circuit board
Secured by flour plastic tabs 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.
8.07 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.
8.08 Short spares list
KEY NO. DESCRIPTION
(from fi g 2 )
14 Safety Valve C/W Manifold
16 Fan assembly
34 Central Heating Flow Temperature Sensor
42 Domestic Hot Water Flow Temperature Sensor
43 Air Pressure Switch
44 Gas Valve - VK4105G
49 Overheat Safety Thermostat 100°C
50 High Limit Thermostat 88°C
81 Ignition Electrode
82 Flame Sensing Electrode
136 Flow Meter C/W Elbow
Main PCB MF03
27 Heat Exchanger
38
Ferroli F24
PART NO. G.C. NO.
805880 E39-485
800480 E23-851
800320 E23-839
800320 E23-839
800150 E23-840
808000 E23-768
801240 386-815
800160 386-577
806258 E26-348
801438 E23-855
805910 E39-465
805900 E39-470
807480 E77-470