Faults
Greenstar – 6721822579 (2021/01)
74
17.2 Faults that are shown on the display
Display Description Elimination
A7 DHW temperature sensor defective. ▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Insert code plug correctly; replace if defective.
A8 Communication fault. ▶ Check BUS communications wiring, replace if defective.
▶ Check control, replace if defective.
Ad DHW tank temperature not detected.
The DHW tank temperature sensor was recognized
before the connection was lost.
▶ Check DHW tank temperature sensor and connecting lead, replace if
defective.
▶ Reset the boiler to the factory default settings ( service function 8.E).
b1 Code plug not detected. ▶ Insert code plug correctly; replace if defective.
b2/b3/b4/
b5/b6
Internal data error. ▶ Reset boiler to the factory default setting ( service function 8.E).
b7 Fault in the burner controls. ▶ Reset boiler to factory to default setting ( service function 8.E).
C6 Fan not running. ▶ Check fan leads and fan, replace if defective.
CC Outdoor temperature sensor not recognized. ▶ Check outdoor temperature sensor and leads for interruptions, replace if
defective.
▶ Verify the outdoor temperature sensor is connected to terminals A and F.
d3 Temperature high limit defective.
External guard has tripped.
Temperature limiter locked out.
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Temperature guard TB1 has tripped. Check if jumper across 8-9 or PR-P0
is missing.
▶ Reset external temperature limiter (if installed).Reset LWCO (if installed).
▶ Reset pressure regulator (if installed).
d5 External supply temperature sensor defective (low-loss
header).
The external supply temperature sensor was recognized
on the BUS and then reconnected to the appropriate
terminal.
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Check whether only one temperature sensor is connected; otherwise
remove second temperature sensor.
▶ Reset the boiler to the factory default settings ( service function 8.E).
E2 Supply temperature sensor defective. ▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
E3 Additional supply temperature sensor defective. ▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
E9 Heat exchanger safety high limit or flue gas temperature
limiter has tripped.
▶ Check flue gas safety high limit and leads for interruptions or shorts, and
replace if defective.
▶ Check heat exchanger safety high limit and leads for interruptions or shorts,
and replace if defective.
▶ Check the operating pressure.
▶ Check temperature limit; replace if defective.
▶ Check pump capacitor; replace pump if defective.
▶ Check PCB fuse, replace if blown (6.3 A fuse according to IEC default).
▶ Purge the appliance.
▶ Check heat exchanger on the DHW side; replace if clogged.
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