Bosch Worcester 15SBi Installation And Servicing Instructions page 34

No
Does the burner
ignite? (use spy glass
to observe flame)
Yes
Does the flame
No
continue for more
than 10 seconds?
NOTE: Reverse
live/neutral polarity
will cause this fault.
And system should
be cool.
Yes
Yes
Are the spark
No
electrodes and gap
connections in
good order?
Yes
Replace control board.
(Section 15.4.9)
(LOCKOUT will occur
after 8 seconds)
Is gas supply
connected and at
the correct pressure?
Yes
Press facia button to
reset the LOCKOUT.
With a new boiler
demand is there
approx 210V DC
across pins 1& 4 of
connector X3 during
spark sequence?
Yes
Replace the gas valve
(Section 15.4.1)
Switch off mains
No
supply. Remove boiler
front panel and
combustion chamber
cover. Is the sense
electrode and lead in
good condition and is
gap correct?
Yes
Check the burner
ports are clear and
clean the burner if
necessary.
Extract control
board from facia. Is
No
there continuity
from flame sense
electrode to board
connector?
Yes
Replace control board.
(Section 15.4.9)
Repair or replace
electrodes or leads.
No
Rectify gas supply
problem.
No
Replace control board.
(Section 15.4.9)
Repair or replace
flame sensor or
wiring.
34