4.13 NO DISPLAY
Is there 230 V AC to the boiler at L and N?
YES
NO
Supply power to the boiler
Is the wiring from the terminal block to the PCB
connected securely?
YES
NO
Connect the wiring from the terminal block to the
PCB securely
Replace the PCB
L
N
4.14 DHW THERMISTOR FAULT
Disconnect the DHW thermistor electrical connection.
Check the resistance using a suitable multi-meter
connected across the thermistor’s terminal pins.
Temperature
Resistance kΩ
25
o
C
9.7 – 10.3
60
o
C
2.4 – 2.6
Is the thermistor value correct?
YES
NO
Fit a new thermistor
Is there continuity between the PCB and the
Thermistor?
YES
NO
Check and replace wiring as necessary.
Replace the PCB?
COMBI
HEA
T / SYSTEM
SL1
L
IN
L
IN
SL2
OPTIONAL
FROST STAT
ROOM
STAT/
TIMER L N
MAINS IN
UIN
230010 A01
L N
MAINS IN
62
Installation and Servicing
Section 4 - Fault Finding
FAUL
T FINDING