Bosch 12/18 Instruction Manual page 46

PROBLEM CAUSE
FAULTY BOILER
OPERATION:
Noisy operation Pump noise from air in pump or
worn pump
Worn motor bearings
Fan out of balance
Boiling Faulty boiler thermostat
Short circuit boiler thermostat
Thermostat bulb not fully home in
pocket
No primary water circulation
Short Cycling Burner rating incorrect
Boiler thermostat differential
incorrect
External controls not operating
correctly
OIL SMELLS: Blocked flue, fumes on startup
Oil soaked boiler, faulty burner
operation, numerous lockouts
Odour in cabinet, oil leaks from
pipework, flexible hoses
connections
45
FAULT FINDING
REMEDY
Bleed air from pump or replace pump
Replace motor
Replace fan
Replace if necessary
Take out of circuit to check
Ensure bulb is pushed fully home
Check system / circulating pump
Correct burner rating
Replace boiler thermostat
Check and correct external controls
Check seals/gaskets
Rectify burner operation and lockouts
Rectify oil leaks, replace components if
necessary
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER GREENSTAR HEATSLAVE EXTERNAL 12/18-18/25-25/32
FAULT FINDING
8 716 113 389b (09/07)