4 30 High

Vokera 4 30 Fault Code

Also written as 430 — same fault.

The Vokera 4 30 fault code means: your boiler has detected that the water leaving the unit is significantly hotter than the water returning, meaning your heating system is currently struggling to circulate heat effectively.. It appears on 1 Vokera model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Difference between flow & return temperature too high
Typical repair cost £120-250 (including labour)

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 4 30 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vokera 4 30 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026