Fault Finding And Diagnosis; Fault Finding - Bosch WORCESTER GREENSTAR Ri ErP Series Installation, Commissioning And Servicing Instructions

FAULT FINDING AND DIAGNOSIS

8 FAULT FINDING AND DIAGNOSIS
8.1

FAULT FINDING

This fault finding information is for guidance only. Worcester cannot be held responsible for costs incurred by persons not deemed to
be competent.
The electronic control system for this boiler incorporates a blue central indicator. This normally confirms the permanent mains supply but, by flashing
at different rates during a fault, provides a guide to the cause as listed.This fault finding system assumes that the appliance has been operating normally
until the time of failure (i.e. not a first installation error).PRELIMINARY CHECKS: Preliminary electrical system checks are the first electrical checks to
be carried out during a fault-finding procedure. On completion of the Service/Fault-Finding task which has required the breaking and remaking of
electrical connections, check:
(a) EARTH CONTINUITY, (b) SHORT CIRCUIT CHECK, (c) POLARITY and (d) RESISTANCE TO EARTH.
Blue light
indication Fault
No light No power at control
board
Light ON Boiler ON but not
operating during
demand
Slow flash Ignition lockout
(mostly off,
flashes on)
Slow flash Flue overheat
(mostly on,
flashes off)
Heat exchanger overheat ▶ Heat exchanger blocked
Flue pressure switch
Fast flash Volatile lockout (sensor,
fan or code plug)
2 pulses
5 pulses
Table 32 Fault finding
50
Possible solution/check
Permanent mains supply to boiler.
Boiler mains switch ON.
Fuse F1 - 2A Slow blow.
Fuse F2 - 1.25A Anti-surge.
Transformer (both coils below 100 Ω.
Otherwise replace control board.
Live demand at ST2 terminal L - is there a demand?
R
Manual bypass is open.
If CH is working check HW controls
If HW is working check CH controls (i.e. external diverter valve, frost stat, room stat/programmer.
Otherwise replace board.
▶ Gas present and at correct pressure?
▶ Gas valve
– Check that there is 35V d.c. to each solenoid
– Check the resistance of each solenoid:
Top solenoid = 380 Ω ± 10% (342 - 418 Ω)
Bottom solenoid = 190 Ω ± 10% (171 - 209 Ω)
▶ Combustion CO level.
2
▶ Flue condition.
– Blocked flue?
▶ Blocked condensate pipe or frozen condensate.
▶ Gas valve adjustment.
▶ Ignition electrodes/harness/connections.
– Check for condition and resistance of leads
(approximately 2100 Ω)
▶ Otherwise replace control board
Flue temperature too high.
▶ Heat exchanger baffles removed and not refitted.
▶ Water pressure
▶ All air vented
▶ Pump/harness/connections.
▶ Water leaks/blockage
▶ Safety thermostats/low voltage wiring harness/connections
▶ Otherwise replace control board
Blockage in the flue system.
▶ Temperature sensors
– Check condition and continuity of leads
– Check resistance of sensor (8k - 20k Ω)
▶ Fan
– 230V A.C. across the live (purple) and neutral (brown)
▶ Fan lead
– Check continuity
▶ Code plug
– Is code plug missing or not inserted properly.
Service mode switch in min. position
Service mode switch in max. position
Greenstar Ri ErP - 6 720 813 283 (2016/07)