Hot water NTC sensor defective. Check hot water NTC sensor and connecting lead for circuit breaks/short circuits.
Worcester Bosch Greenstar 30 CDi System Fault codes & diagnostics
11 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify.All 11 documented codes
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Break in communication to TD200 or/and RT10. Check electrical connections.
Code plug not detected. Insert code plug correctly, test and replace if necessary.
Fan speed too low. Check fan lead and connector, and fan; replace as necessary.
CH flow NTC sensor defective. Check CH flow NTC sensor and connecting lead.
Safety temp. limiter in CH flow has tripped. Check system pressure, check safety temp. limiters, check pump operation, check fuse on pcb, bleed appliance.
Flame not detected/Ignition lockout. Is gas cock turned on? Check gas supply pressure, power supply, igniter electrode and lead, ionisation sensing electrode and lead and CO2 level. Check the condition of the flue, is it blocked? Check the condensate pipe, is it blocked or frozen?
Internal error. Check electrical connector contacts, programmer inter-face module ignition leads are not loose; replace pcb if necessary.
Flame detected even though appliance switched off. Check electrode assembly, dry pcb. Flue clear?
Flame detected after gas shut off. Check gas valve and wiring to gas valve. Clean condensation trap and check electrode assembly. Flue clear?
Reset button pressed by mistake. Press reset button again