Troubleshooting
63
Faults are indicated by a flashing fault
code with fault code sysmbol “U” and
the reset button is illuminated.
For fault code explanations see the
following table.
Diagnostics table: Faults with fault display on control unit
Fault mes-
sage in dis-
play window
System behavior Cause Corrective measures
0b
Burner blocked Insufficient water flow.
Incorrect flow direction.
Defective flow switch.
Check proper heating circuit pump
size and operation.
Check flow direction.
Check flow switch connection cable.
0c
Burner blocked Insufficient power supply Contact your local hydro company.
30
Burner blocked Boiler temperature sensor shorted
out
Check the boiler temperature sensor
(see page 65).
38
Burner blocked Boiler temperature sensor lead break Check the boiler temperature sensor
(see page 65).
b1
Control mode Communication fault - internal pro-
gramming unit
Check connections and replace the
control unit if necessary.
b5
Control mode Internal fault Replace control unit.
e4
Burner blocked Fault with the supply voltage (power
pump module)
Check connections. Replace control
unit.
e5
Burner blocked Internal fault Check ignition and ionization elec-
trodes and leads.
Press “Reset”.
e6
Burner blocked Water pressure too low Top up water .
f0
Burner blocked Internal fault Replace control unit.
f2
Burner in fault mode Fixed high limit tripped Check the heating system water
level. Check the circulation pump
operation. Vent the heating system
of air. Check the fixed high limit and
leads.
Press “Reset”.
f3
Burner in fault mode The flame signal is already present at
burner start
Check the ionization electrode and
leads.
Press “Reset”.
f4
Burner in fault mode No flame signal is present Check the ionization electrode and
leads, check the gas pressure, check
the gas combination valve, control
unit and condensate drain see page
56).
Press “Reset”.
f5
Burner blocked Faulty air pressure switch Check the air pressure switch and
the interconnecting cable.
Check the burner air/gas
mixture damper. Reference the
Burner Damper Replacement
Instructions.
Diagnosis
(continued)
5581 775 1.35581 775 1.3
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