BoilerFaultCodesIdeal 430 Fault Code
The Ideal 430 fault code means: your boiler has detected that water is moving too slowly or not at all through the system, causing a heat imbalance that has triggered a safety shutdown.. It appears on 2 Ideal models in our database.
Technical description: Maximum difference between T1 and T2 exceeded
What causes the Ideal 430 fault?
This fault occurs when the boiler's internal sensors detect that the outgoing water is significantly hotter than the returning water, suggesting a lack of circulation. The most common reason is a failed or stuck pump, though it can also be triggered by air trapped in the system or a blockage in the pipework. In some cases, a build-up of sludge or debris within the heat exchanger prevents the water from moving through the boiler fast enough to carry the heat away.
This fault often appears during the first few cold days of autumn when a pump that has been idle all summer fails to spin back up.
DIY fix possible
Check that your central heating valves and all radiator valves are fully openEnsure there is no air trapped in the system by bleeding your radiatorsCheck if the system pressure gauge is between 1 and 1.5 bar
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Gas Safe Register →Ideal models that show the 430 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 430 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026