OVERHEAT LOCKOUT error code
OVERHEAT LOCKOUT – legacy Keston Heat 45/55 error code
What does Keston Legacy Keston Heat 45 and 55 commercial boilers OVERHEAT LOCKOUT mean?
Keston documents “Boiler overheat lockout” for the legacy Heat 45, 55, 45P and 55P controller. This is a distinct earlier product generation from the Heat² range and must be matched to the exact boiler display.
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 Legacy Keston Heat 45 and 55 commercial boilers OVERHEAT LOCKOUT error code indicates keston documents “Boiler overheat lockout” for the legacy Heat 45, 55, 45P and 55P controller. This is a distinct earlier product generation from the Heat² range and must be matched to the exact boiler display. 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 boiler displays OVERHEAT LOCKOUT; burner or heating operation may be blocked or locked out until the underlying condition is corrected.
Common causes
Possible causes are associated with boiler overheat lockout, including the related circulation, sensor, combustion, fan, electrical, safety-interlock or controller circuit described in the official fault-finding 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
Fill and vent the system, confirm valves are open and have the pump and flow/return temperature differential checked.
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 OVERHEAT LOCKOUT reappears, note when it happens and give that information to the service engineer.
Reset instructions
Record the exact message first. Reset only after the underlying cause has been corrected and never continue resetting a recurring fault.
Applicable products and models
Legacy Keston Heat 45 and 55 commercial boilersHeat 45; Heat 55; Heat 45P; Heat 55PLegacy generation to 2020When to contact a professional
Contact Keston commercial support or a suitably qualified Gas Safe registered engineer when the message persists or requires internal tests, measurements, wiring checks or component replacement.
Frequently asked questions
What does Keston Legacy Keston Heat 45 and 55 commercial boilers OVERHEAT LOCKOUT mean?
Keston documents “Boiler overheat lockout” for the legacy Heat 45, 55, 45P and 55P controller. This is a distinct earlier product generation from the Heat² range and must be matched to the exact boiler display.
Can I fix Keston Legacy Keston Heat 45 and 55 commercial boilers OVERHEAT 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 OVERHEAT LOCKOUT?
Record the exact message first. Reset only after the underlying cause has been corrected and never continue resetting a recurring fault.
When should I arrange a repair?
Contact Keston commercial support or a suitably qualified Gas Safe registered engineer when the message persists or requires internal tests, measurements, wiring checks or component replacement.