FLOW THERMISTOR FAULT error code
FLOW THERMISTOR FAULT – Keston System² S30 error code
What does Keston Keston System² S30 gas boiler FLOW THERMISTOR FAULT mean?
Keston documents “Flow thermistor fault” for the System² S30. This display message identifies a boiler-detected fault or safety condition; confirm the exact wording on the appliance before taking action.
The code identifies the condition detected by the product; it does not always identify the failed component on its own. Confirm the full code and exact model before ordering parts or attempting a reset.
The Keston Keston System² S30 gas boiler FLOW THERMISTOR FAULT error code indicates keston documents “Flow thermistor fault” for the System² S30. This display message identifies a boiler-detected fault or safety condition; confirm the exact wording on the appliance before taking action. This guide explains what the code means, the symptoms and likely causes, the checks that are safe to make, and when to stop and arrange an authorised repair.
Symptoms you may notice
The System² S30 displays FLOW THERMISTOR FAULT; central-heating or cylinder-heating operation may stop, lock out or remain restricted until the condition is corrected.
Common causes
Possible causes are associated with flow thermistor fault, including the related sensor, supply, safety, combustion, circulation or controller circuit identified by the official Keston guide.
Before you start troubleshooting
Use the display, rating label or product menu to confirm the exact model. Similar-looking codes can have different meanings across product generations and regions.
- Record the complete code before switching the equipment off.
- Check only user-accessible controls, filters and external connections described in the manual.
- Do not open gas, refrigerant, combustion or electrical compartments.
Troubleshooting steps
Contact an installer to test the flow-temperature sensor circuit and associated wiring.
Can you fix this error code yourself?
The safest next step depends on the exact model and the cause behind the code. External checks may help, but a returning fault needs professional diagnosis.
A successful reset is not proof that the underlying issue is fixed. If FLOW THERMISTOR FAULT reappears, note when it happens and give that information to the service engineer.
Reset instructions
Do not reset this fault unless directed by a competent engineer or the official display sequence.
Applicable products and models
Keston System² S30 gas boilerSystem² S302022 onwardWhen to contact a professional
Contact Keston support or a Gas Safe registered engineer when the message persists, returns after a permitted user check, involves combustion or electrical safety, or requires internal access.
Frequently asked questions
What does Keston Keston System² S30 gas boiler FLOW THERMISTOR FAULT mean?
Keston documents “Flow thermistor fault” for the System² S30. This display message identifies a boiler-detected fault or safety condition; confirm the exact wording on the appliance before taking action.
Can I fix Keston Keston System² S30 gas boiler FLOW THERMISTOR FAULT myself?
Some external checks may be suitable for the user, but the result depends on the exact model and cause. Use the official manual and arrange service if the code returns.
Should I reset the product after code FLOW THERMISTOR FAULT?
Do not reset this fault unless directed by a competent engineer or the official display sequence.
When should I arrange a repair?
Contact Keston support or a Gas Safe registered engineer when the message persists, returns after a permitted user check, involves combustion or electrical safety, or requires internal access.