Verified boiler fault code
Potterton E109 Fault Code (Assure Combi & System)
Precirculation alarm.
Safety disclaimer
Fault code summary
- Manufacturer
- Potterton
- Fault code
- E109
- Fault type
- Circulation, Pump
- Severity
- Not specified
- Reset
- Not specified
- Applicable models
- Potterton Assure Combi, Potterton Assure System
Quick answer
Precirculation alarm.
What does this fault code mean?
Precirculation alarm.
Common causes
- Precirculation alarm.
Symptoms
- The boiler displays E109 and may stop operating.
What can the homeowner safely check?
- Note the code and consult the Potterton instructions.
Boiler reset information
Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Check the primary circulation and pump operation.
Applicable boiler models
Related fault codes
- E09 — Assure Combi & System
Gas valve connection fault.
Read fault code - E10 — Assure Combi & System
External probe fault.
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The boiler maximum temperature was exceeded, or the safety thermostat sensor tripped.
Read fault code - E118 — Assure Combi & System
Water pressure is low, below 0.5 bar.
Read fault code - E12 — Assure Combi & System
Differential water-flow switch fault; the switch is still open.
Read fault code - E125 — Assure Combi & System
Water circulation fault.
Read fault code - E128 — Assure Combi & System
Safety error for frequent loss of flame.
Read fault code - E129 — Assure Combi & System
Safety error for frequent loss of flame with maximum correction during ignition calibration.
Read fault code
Manufacturer documentation
Boiler Error Codes | BaxiPotterton Assure Combi & System — E109: Precirculation alarm.
Last verified
2026-09-12
Frequently asked questions
What does Potterton E109 mean?
Precirculation alarm.