DOMINA 80 E
55
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 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.
8.08 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
PART NO.
G.C. NO.
(from fig 2 )
14
Safety Valve
800130
386-816
16
Fan
800480
E23-851
34
Central Heating Flow Temperature Sensor
800320
E23-839
42
Domestic Hot Water Flow Temperature
Sensor
800320
E23-839
43
Air Pressure Switch
800150
E23-840
44
Honeywell Gas Valve
800266
E23-768
49
Overheat Safety Thermostat 100
°
C
801270
386-815
50
High Limit Thermostat 88
°
C
800160
386-577
81
Ignition Electrode C/N fixing Bracket
806460
82
Flame Sensing Electrode
801438
E23-855
136
Flow Meter
803430
E03-340
Main PCB MF02
801873
E23-862
Ignition PCB
800655
E23-848
27
Heat Exchanger
802180
E23-919