Bosch 25/32kW - Manual (Page 48)

Boiler not operating
with a
heating / hot water demand
Burner
motor runs?
L
o
ckout
within 1 second? Replace
control b
o
x
Replace
motor/pump Chec
k b
oiler
controls &
supply
Replace
motor
L & N
to
control b
o
x?
Motor or
pump
seized?
Photo cell functional?
S
olenoid
coil
functional (100
Ω
)?
Replace photo cell
Motor gives 50 V
olts on
white wire?
L
o
ckout
after 12 sec
purge?
Replace
control b
ox
Replace
solenoid coil
Replace
motor
Ignition
spark
proved?
Oil to pump?
Drive
coupling broken?
P
urge
pressure 1-2 bar?
P
ump
produces pressure?
Replace
pump stem
valve,
pressure
OK
?
Replace
solenoid coil
Pipe to nozzle
holder O
K
?
Replace
nozzle
Replace oil
pump
Replace
control b
o
x
Eectrodes &
leads O
K
?
Yes No
NO
Yes
No Yes No
Yes
Yes
No No
Yes Yes
No No Yes
Yes
No Yes
Motor 4
0
Ω
between blue &
blac
k wires ?
Replace
control b
o
x
Yes
Yes No
Yes No Yes No
No No
Yes
No
Nozzle
atomising
fuel?
Combustion
air setting
correct?
Yes
Yes
Combustion
head set correctly?
S
olenoid operating?
Increase the pump
pressure, pressure O
K
?
S
olenoid
coil
functional (100
Ω
)?
No
Coil lead
OK
?
Yes
Yes
Replace
control b
o
x
No
Remove
burner
snorkle tube
& retest.
Lights O
K
?
Flame off &
re-lights?
Yes
Photo cell functional?
No Yes
Replace photo cell
No
Boiler or flue
bloc
ked
No
Reseal B
F
Yes
Replace
control b
ox
Yes
Replace
electrodes/
leads
No
Unbloc
k or
replace pipe
No
Reset air
setting
No
Reset
combustion
head
No
FAULT FINDING LOGIC FOR
535 SE/LD RDB CONTROL BOX
All resist
ance measurements are actual measured values and some variation is to be expected
, therefore measured
values should be similar to but not necess
arily identical to the given values
.
T
he operation of the photo cell can be tested by measuring the resist
ance across the photo cell
, it should be a high
resist
ance (
greater than 1
0
M
Ω
or open circuit
) in the dark and low resist
ance (3k
Ω
or less
) in light
.
Burners on balanced flue systems can recirculate flue products resulting in the burner cycling
, if this happens c
hec
k the
flue system integrity and the terminal position
.
These fault finding charts are provided to assist competent and suitably qualified engineers
to locate and rectify faults. Whilst every effort has been taken to ensure the information
given is correct and complete we cannot guarantee that every eventuality has been
covered.
Worcester, Bosch Group cannot be held responsible for costs incurred by persons not
deemed to be competent.
F
A
UL
T
F
IND
IN
G
& D
IA
G
R
A
M
S
FAULT FINDING
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR HEATSLAVE EXTERNAL 12/18-18/25-25/32
8 716 113 389b (09/07)
47