Worcester GREENSTAR 12i Instruction Manual page 76

If in the unlikely event the boiler does not give
complete satisfaction, before calling for a service
engineer, the installer should check the following:-
For boilers with external diverter valves and
controls
No Central Heating but Hot Water OK
Unlikely to be a boiler fault, please ask your electrician to check the external
controls.
No Hot Water but Central Heating OK
Unlikely to be a boiler fault, please ask your electrician to check the external
controls.
No HW or CH demand
Is there a demand from external controls? To eliminate the boiler as a fault,
remove the switched live from the wiring centre to L
between the Ls and L . If the boiler and pump run normally then it is likely
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there is a fault with the external controls. Please contact your electrician.
For boilers with internal diverter valve and controls
No Central Heating but Hot Water OK
Remove the room stat wiring from Ls, L
link between Ls and L , if the CH now works there is likely to be a problem
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with the room stat or wiring to it.
No Hot Water but Central Heating OK
Remove the cylinder stat wiring from 8 and 10 on the terminal block ST8. Fit
link across 8 and 10.
For all boilers with internal or external controls
Burner lights then goes out in DHW or CH mode
Does the boiler run normally with the front cover off and then fail
when the cover is put back on?
If yes there is likely to be a flue problem - either the air inlet is blocked or the
inner flue is leaking flue gases into the air inlet.
Boiler noisy or going to overheat
1. Was the system flushed?
2. Has the pump been bled and the dust cap released.
General checks
1. Is all the air bled from the gas supply?
2. Is all the air bled from the primary water system?
3. Is there 230v ac across the boiler live and neutral terminals?
(L & N on ST10)
4. Is the polarity correct?
5. Is the incoming gas pressure at least 18mbar with the boiler at maximum
output?
Dedicated to heating comfort
Worcester, Bosch Group
Cotswold Way, Warndon, Worcester WR4 9SW.
Tel. 01905 754624 Fax. 01905 754619
Worcester, Bosch Group is a brand name of Bosch Thermotechnology Ltd.
www.worcester-bosch.co.uk
8 716 115 167b (03/2009)
on ST10, then fit a link
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and N on terminal block ST10. Fit a
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Pack Number
CONTACT INFORMATION
WORCESTER, BOSCH GROUP:
TECHNICAL: 08705 266241
SERVICE: 08457 256206
SPARES: 01905 752571
LITERATURE: 01905 752556
TRAINING: 01905 752526
SALES: 01905 752640
WEBSITE: www.worcester-bosch.co.uk