RED-LOCKOUT error code
Red lockout light – Keston 340 boiler fault indication
What does Keston Keston 340 commercial condensing boiler RED-LOCKOUT mean?
Keston documents a red lockout lamp for each module of the 340. If the red lamp alone remains illuminated, the module has failed to complete or maintain its firing sequence and is locked out. This is an indicator state rather than an alphanumeric display code.
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 340 commercial condensing boiler RED-LOCKOUT error code indicates keston documents a red lockout lamp for each module of the 340. If the red lamp alone remains illuminated, the module has failed to complete or maintain its firing sequence and is locked out. This is an indicator state rather than an alphanumeric display code. 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 red module lockout lamp stays illuminated while the green run lamp is extinguished. The affected module does not fire, so the 99.0 kW output at 80/60°C boiler may provide reduced or no heat depending on the state of its other module and system demand.
Common causes
The official fault-finding sequence covers interrupted gas supply, an air-pressure proving problem, blocked air intake, flue or condensate path, burner restriction, ignition electrode or HT-lead fault, gas-valve or control-box fault, tripped temperature protection, low gas pressure, low water pressure, incorrect flow, fan or relay failure, or cabinet over-temperature protection.
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
Confirm that the external electrical and gas supplies are available and record which module is locked out. Do not remove the casing. A qualified engineer should follow the official fault-finding flowchart and test the safety circuit, fan, pressure switches, ignition, gas valve, thermostats and 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 RED-LOCKOUT reappears, note when it happens and give that information to the service engineer.
Reset instructions
Turn the affected module off, wait at least 20 seconds, then turn it on once as described by Keston. If lockout recurs immediately or the module does not relight, isolate it and arrange professional service; do not repeatedly reset it.
Applicable products and models
Keston 340 commercial condensing boiler3401999 product generationWhen to contact a professional
A suitably qualified Gas Safe registered commercial heating engineer should diagnose a persistent lockout. Provide the model, affected module and lamp sequence, and give the engineer the official Keston 260/340 service manual.
Frequently asked questions
What does Keston Keston 340 commercial condensing boiler RED-LOCKOUT mean?
Keston documents a red lockout lamp for each module of the 340. If the red lamp alone remains illuminated, the module has failed to complete or maintain its firing sequence and is locked out. This is an indicator state rather than an alphanumeric display code.
Can I fix Keston Keston 340 commercial condensing boiler RED-LOCKOUT 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 RED-LOCKOUT?
Turn the affected module off, wait at least 20 seconds, then turn it on once as described by Keston. If lockout recurs immediately or the module does not relight, isolate it and arrange professional service; do not repeatedly reset it.
When should I arrange a repair?
A suitably qualified Gas Safe registered commercial heating engineer should diagnose a persistent lockout. Provide the model, affected module and lamp sequence, and give the engineer the official Keston 260/340 service manual.