Boiler fault codes
Worcester Bosch Boiler Fault Codes Explained
Worcester Bosch boiler fault codes come in two formats. Older Greenstar boilers show a display code with a three-digit cause code, such as EA and 227. Newer models such as the Greenstar 8000 Life show the number alone. Controls have their own codes, such as A21. Note the full code before any reset, then find it below.
How to read a Worcester display
On Greenstar i and CDi boilers the display code tells you the area of the fault and the cause code narrows it down. The same display code can carry several causes: in the Greenstar CDi Compact manual, EA covers 227 (no flame detected after ignition), 229 (flame lost while running), 234 (gas valve error) and 261 (ignition timing error). Always write down both parts.
Newer boilers list the number with a short text. On the Greenstar 8000 Life, 200, 201 and 203 are simply the boiler in heating mode, hot water mode and standby, so a number on screen is not always a fault. Codes such as 224 (safety temperature limiter tripped), 227 (no flame after ignition) and 1017 (water pressure too low) are the ones that stop the boiler and set the blue lockout light flashing.
Codes starting with A, such as A21, usually show on the heating controls rather than the boiler. A21 on a Comfort RF thermostat is a lost radio link with the receiver, and fault 1101 is widely reported as the same kind of lost thermostat link.
Which Worcester codes can you clear yourself?
Low pressure is the usual one. If the gauge has dropped below 1 bar, top the system up and reset once. Controls codes clear once batteries, power or signal are restored. SE on the display is not a fault either: it is a service reminder that appears after roughly a year of running hours.
A no-flame lockout such as EA 227 is worth one reset after checking the gas is on at the hob and, on a prepayment meter, that there is credit. In freezing weather a frozen condensate pipe outside is a common trigger and can be thawed with warm, not boiling, water.
Which codes mean calling an engineer?
Overheat codes such as E9, fan codes such as C6, and any lockout that returns after one reset mean a part inside the casing: the fan, gas valve, electrodes, sensors or control board. Leave the case closed. Gas work is carried out by Gas Safe registered engineers.
If you smell gas, open windows, turn the gas off at the meter if safe, use no switches, then leave the property and call the National Gas Emergency Service on 0800 111 999. For anything else, our Worcester boiler repair visits start with the £60 call-out, and the repair price is agreed on site before any work starts.
| Code | What it means | Can you clear it yourself? |
|---|---|---|
| EA 227 | No flame sensed after ignition, so the boiler locked out | Yes, once; call if it returns |
| EA 229 | Flame lost while the boiler was running | Yes, once; call if it returns |
| E9 | An overheat safety device has tripped; the cause code says which | No, call an engineer |
| C6 | Fan running at the wrong speed: 215 too fast, 216 too slow | No, call an engineer |
| E2 | Flow temperature sensor shorted (222) or disconnected (223) | No, call an engineer |
| CE 207 | Water pressure too low (Greenstar CDi Compact) | Yes, once; call if it returns |
| CE 266 | No pressure change detected when the pump starts | No, call an engineer |
| 1017 | Water pressure too low (Greenstar 8000 Life, 4000, 2000) | Yes, once; call if it returns |
| 227 | No flame after ignition (Greenstar 8000 Life, 2000) | Yes, once; call if it returns |
| 224 | Overheat or flue gas thermostat tripped (Greenstar 8000 Life, 2000) | No, call an engineer |
| A21 | Wireless room thermostat has lost its radio link | Yes, once; call if it returns |
| SE | Service reminder after about a year of running; not a fault | No, call an engineer |
Worcester Bosch codes explained
- 1101Fault 1101 is widely reported as the boiler losing contact with its room thermostat or programmer, so it stops getting heating demands. Worcester does not list 1101 in the control manuals we checked, so treat it as a controls fault and note every code on screen.
- A21On Worcester Comfort RF wireless controls, A21 means the room thermostat has lost its radio link with the receiver, so the boiler is no longer getting heating demands. On a wired Sense I control, A21 with sub-code 1001 means the control has been set up wrongly instead.
- C6The boiler measured its fan running at the wrong speed and locked out, because it cannot burn gas safely without the right amount of air. On Greenstar models, 215 after C6 means too fast and 216 means too slow.
- E9An overheat safety device inside the boiler has tripped and the boiler has locked out to protect itself. The three-digit cause code shown with E9 says which sensor tripped and why.
- EA 227The boiler sparked to light the burner but never sensed a flame, so it shut down and locked out. Worcester lists 227 as "no flame signal after ignition"; it stays locked until someone presses reset.
Questions people ask
How many times should I reset a Worcester boiler?
Once. If the same code returns, a second reset rarely helps and wipes information the engineer can use. Note the code and when it came back.
Why does my Worcester show a code but still work?
Some numbers are status messages, not faults. On the Greenstar 8000 Life, 200 just means the boiler is in heating mode, and SE on older Greenstar displays is a service reminder.