- Boilers
- Gas boiler
E9
Worcester E9 on a gas boiler: safety temperature limiter tripped
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On Greenstar CDi boilers, E9 means a safety temperature limiter has tripped and the boiler has locked out. Check the pressure gauge reads 1 to 2 bar, top up if low, reset once for 3 seconds and call a Gas Safe engineer if E9 returns.
Safety first
Stop and check this first
- Do not chain resets with E9: it is a temperature safety cut. If it returns, leave the boiler off until an engineer has checked it.
- This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
- If you smell gas: do not smoke or strike matches, do not operate electrical switches or unplug anything, do not use the phone or ring doorbells. Turn off the gas at the meter, open windows and doors, warn your neighbours and leave. Well away from the building, call the National Gas Emergency Service on 0800 111 999.
Safe checks you can perform
- Pressure gauge reading
- One reset
- Radiators and noise
- Safety temperature circuit test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Circulation and pump check
- Do not attempt this professional task: Limiter continuity tests
- Do not attempt this professional task: Flue and combustion check
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Circulation and pump check
What they doThe engineer checks system pressure and whether the pump is seized, freeing or replacing it and refilling and venting the system.
They must show youpressure and pump running.
In writingwhat was found and corrected.
Limiter continuity tests
What they doWith the power off, the engineer measures continuity of the flue safety temperature limiter and the CH flow safety temperature limiter, and of the harness.
They must show youwhich limiter was open.
In writingthe test results and the reference of any part replaced.
Flue and combustion check
What they doBecause one limiter guards the flue, the engineer checks the flue and measures CO2 in the flue gas with an analyser.
They must show youthe flue inspection and the analyser reading.
In writingthe measured values against Worcester's figures.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Pressure gauge reading
- Who:
- you.
- How:
- with the boiler cold, read the gauge. The service booklet expects 1 to 2 bar on a sealed system; Worcester's user guide gives 1.5 bar as the optimum.
- Result that matters:
- whether pressure is within 1 to 2 bar.
- If it is below 1 bar:
- re-pressurise with the filling link to 1.5 bar as the user guide shows; low water fits E9.
- If it is within range:
- overheating from lack of water is less likely.
- Evidence to keep:
- a photo of the gauge before and after topping up.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
One reset
- Who:
- you.
- How:
- press the reset button for three seconds.
- Result that matters:
- whether the boiler restarts and E9 stays away.
- If E9 returns:
- stop; the limiter keeps tripping and Worcester says to call a Gas Safe registered engineer.
- If it runs:
- note it; a repeat after heating for a while points to circulation.
- Evidence to keep:
- a note of each reset and what the boiler was doing.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Radiators and noise
- Who:
- you.
- How:
- with heating on, feel whether radiators warm up and listen for a pump that hums without moving water.
- Result that matters:
- whether water is circulating.
- If radiators stay cold and E9 comes back:
- poor circulation is likely; tell the engineer.
- If radiators heat normally:
- the limiter or wiring become the suspects.
- Evidence to keep:
- a note of cold radiators and noises.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Safety temperature circuit test
- Who:
- a Gas Safe registered engineer.
- How:
- checks the pump, then tests the flue and flow limiters, harness and fuse for continuity.
- Result that matters:
- which part of the circuit is open.
- If a limiter opens with the boiler cold:
- it is replaced.
- If all test correct after real overheating:
- the circulation fault is the real problem.
- Evidence to keep:
- a job sheet listing each test.
Limiters, flue sensors and the PCB are inside the sealed casing; only a Gas Safe registered engineer works on them.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Worcester Bosch
- Product type
- Gas boiler
Known code variants
- 11 E
- 11E
- AEG E9
- AEG hob E9
- Bosch E9 caldera
- Cerapur E9
- E09
- E-9
- E9 Worcester
- error E9 frigorífico Hotpoint
- error E9 frigorífico Indesit
- Error E9 Junkers
- error E9 lavadora Samsung
- frigorífico combi Hotpoint E9 congelador
- frigorífico combi Indesit E9 congelador
- Greenstar E9
- Hotpoint E9 error fridge freezer
- Hotpoint E9 frigorífico
- Hotpoint fridge freezer E9
- Hotpoint fridge freezer E9 freezer high temperature
- Indesit E9 error fridge freezer
- Indesit E9 frigorífico
- Indesit fridge freezer E9
- Indesit fridge freezer E9 freezer high temperature
- Junkers E9
- lavadora Samsung nivel de agua bajo
- placa AEG E9
- placa inducción AEG E9
- Samsung E9 pierde agua
- Samsung E9 water leak
- Samsung lavadora 11E
- Samsung lavadora E9
- Samsung washer 11E
- Samsung washer error E9
- Samsung washer low water level
- Samsung washing machine E9
- Worcester boiler E9 fault
- Worcester Bosch E9
- Worcester E9
What it means
Worcester's user table gives E9 as the safety temperature limiter in the central heating flow having tripped. The service booklet treats it as the safety temperature circuit, which also includes a flue safety temperature limiter. It checks system pressure (1 to 2 bar on sealed systems, water in the feed and expansion tank on open vented ones), a seized pump, disconnected limiter leads, each limiter's continuity, the harness, a fuse on the PCB and finally the PCB. E9 alone does not show which of these tripped the circuit.
Warnings and stop conditions
- Higheditorial warning
Do not chain resets with E9: it is a temperature safety cut. If it returns, leave the boiler off until an engineer has checked it.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
- Higheditorial warning
This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
Evidence: HSE gas safety for homeowners · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
- Criticalsource verified
If you smell gas: do not smoke or strike matches, do not operate electrical switches or unplug anything, do not use the phone or ring doorbells. Turn off the gas at the meter, open windows and doors, warn your neighbours and leave. Well away from the building, call the National Gas Emergency Service on 0800 111 999.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Symptoms and causes
Probable causes · in order
- Low water or poor circulationCommon
Fits when pressure is under 1 bar or the pump is seized: the water overheats and the limiter cuts out. Topping up or freeing the pump clears it.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
- Flue or flow limiter, or its leadPossible
Fits when pressure and pump are fine; the engineer tests each limiter and its lead for continuity.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
- Harness, fuse or PCBLess common
Fits when the limiters test correct; the booklet then checks the harness, fuse SI 3 and the PCB.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Virtual technician
Does E9 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Health and Safety Executive · official_doc
- 2
Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Worcester Bosch · 2014 · manual
- 3
Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Worcester Bosch · 2014 · manual
Was this entry useful?