Ferroli TEMPRA 30 Installation, Service And User Instructions Manual page 38

TEMPRA 30
8.04 Temperature sensors (thermistors)
Identical, but individual, negative temperature co-effi cient (NTC) thermistors are fi tted in the C.H. 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.. The sensors are fi tted 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 fl our 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 rectifi er. 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.
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