BoilerFaultCodesIdeal No flow Fault Code
Also written as NOFLOW — same fault.
The Ideal No flow fault code means: your boiler is not starting because it cannot detect water moving through the system to prevent overheating.. It appears on 2 Ideal models in our database.
Technical description: Flow switch is not connected or terminals are left disconnected; the boiler will not operate.
What causes the Ideal No flow fault?
This fault occurs when the boiler's internal safety sensor fails to detect water circulating through the heat exchanger. The most common reasons are a physically stuck flow switch, a failed circulation pump that isn't moving the water, or a loose electrical connection in the wiring harness. Without this movement, the boiler shuts down immediately to prevent the internal components from overheating and sustaining damage.
This issue often surfaces at the start of autumn when heating systems are turned back on after sitting idle all summer, which can cause the pump or switch to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the No flow fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal No flow 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