Bosch 12/18 User Manual
FAULT FINDING
PROBLEM
CAUSE
REMEDY
FAULTY BOILER
OPERATION:
OPERATION:
Noisy operation
Pump noise from air in pump or
worn pump
worn pump
Bleed air from pump or replace pump
Worn motor bearings
Replace motor
Fan out of balance
Replace fan
Boiling
Faulty boiler thermostat
Replace if necessary
Short circuit boiler thermostat
Take out of circuit to check
Thermostat bulb not fully home in
pocket
Ensure bulb is pushed fully home
No primary water circulation
Check system / circulating pump
Short Cycling
Burner rating incorrect
Correct burner rating
Boiler thermostat differential
incorrect
incorrect
Replace boiler thermostat
External controls not operating
correctly
correctly
Check and correct external controls
OIL SMELLS:
Blocked flue, fumes on startup
Check seals/gaskets
Oil soaked boiler, faulty burner
operation, numerous lockouts
operation, numerous lockouts
Rectify burner operation and lockouts
Odour in cabinet, oil leaks from
pipework, flexible hoses
connections
pipework, flexible hoses
connections
Rectify oil leaks, replace components if
necessary
necessary
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)
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