Excel HE C24 User Manual page 54

86 ERROR CODE 7 - FLUE GAS OVERHEAT
Can the fault condition be
reset by carrying out the
reset procedure?
YES
Is the system filled and
vented and all isolation
valves open?
YES
Check the value of the
thermistor. Is it OK?
YES
Inspect the heat exchanger
and check for water flow.
Repair as necessary.
Replace thermistor
Fill and vent the system.
Open all isolating valves
87 ERROR CODE 8 - CONDENSATE BLOCKAGE ALARM
Is there condensate in the
recuperator? Check this by
partially unscrewing the
recuperator thermistor (see
Frame 78)
NO
Does the error clear on
reset?
YES
Observe operation and re-
test if necessary.
Is the wiring harness
continuity OK?
YES
Replace Replace
PCB harness
excel HE -
Installation and Servicing
FAULT FINDING
NO
Disconnect and
measure the value of
the recuperator
thermistor.
Approx 10 K @ 25
Approx 3.2K @ 60
NO
Approx 1.1K @ 95
Are the values correct?
NO
Re-connect and measure the
voltage across the thermistor
nominally 3.75V DC.
Is the voltage correct?
Is PCB connector fitted
correctly?
Measure the wiring
harness continuity to the
thermistor. Is it OK?
YES
Remove blockage and
re-test
NO
Measure the resistance of
the recuperator thermistor
Approx 10 K @ 25
Approx 3.2K @ 60
Approx 1.1K @ 95
Is it correct
Re-connect and measure
voltage across thermistor.
Is it 3.75V DC nominal?
NO
YES
Is the connector fitted
correctly to the PCB?
o
C
o
C
o
C
NO
Replace thermistor
YES
YES
NO
NO
YES
YES
NO
o
C
o
C
o
C
NO
Replace thermistor
YES
YES
NO
NO
Replace PCB
Fit and re-test
Replace PCB
Replace harness
Replace PCB
Refit and re-test
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