BoilerFaultCodesVokera E099 Fault Code
The Vokera E099 fault code means: your boiler has detected that the water temperature difference between the outgoing and incoming pipes is outside of the normal expected range, causing it to shut down to prevent damage.. It appears on 10 Vokera models in our database.
Technical description: outlet/return line probe differential alarm
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Vokera models that show the E099 fault code
Click a model for the full fault code list and model-specific repair notes.
- Pinnacle Combi Repair: £100-350
- Pinnacle System Repair: £0-120
- Synergy Combi Repair: £0-120
- Synergy System Repair: £0-120
- Unica MAX Repair: £120-250
- Unica MAX Combi Repair: £90-250
- Unica MAX System Repair: £0-120
- Vision Plus 35C/40C Repair: £150-300
- Vision S Repair: £120-250
- Vision System Sgc Repair: £150-250
Source
Vokera E099 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
- Vokera Pinnacle Combi manual (PDF)
- Vokera Pinnacle System manual (PDF)
- Vokera Synergy Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026