E81 error code
ACV Compact Condens E81 error code – Flow and return sensor drift
What does ACV Compact Condens commercial gas boilers E81 mean?
ACV documents E81 for Compact Condens 170, 210, 250 and 300 boilers as “Flow and return sensor drift”. The flow and return temperatures are not equal when expected.
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 ACV Compact Condens commercial gas boilers E81 error code indicates aCV documents E81 for Compact Condens 170, 210, 250 and 300 boilers as “Flow and return sensor drift”. The flow and return temperatures are not equal when expected. 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 Compact Condens boiler displays E81 and may enter a soft or hard lockout until the detected condition is corrected.
Common causes
Possible causes include a failed or disconnected sensor, damaged wiring, a loose connector, or a circuit condition outside the controller's expected range.
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
Verify circulation and allow temperatures to equalise. If the appliance does not reset, check the NTC sensors 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 E81 reappears, note when it happens and give that information to the service engineer.
Reset instructions
Use only the reset procedure described in the official Compact Condens manual. Hard lockouts require a manual reset; soft lockouts clear only after their cause is resolved. Do not repeatedly reset a returning fault.
Applicable products and models
Compact Condens commercial gas boilersCompact Condens 170, 210, 250 and 3002018 onwardWhen to contact a professional
Contact an ACV-qualified heating engineer if the code returns, the appliance remains locked out, a safety device has operated, or checks require internal access, test equipment or replacement parts.
Frequently asked questions
What does ACV Compact Condens commercial gas boilers E81 mean?
ACV documents E81 for Compact Condens 170, 210, 250 and 300 boilers as “Flow and return sensor drift”. The flow and return temperatures are not equal when expected.
Can I fix ACV Compact Condens commercial gas boilers E81 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 E81?
Use only the reset procedure described in the official Compact Condens manual. Hard lockouts require a manual reset; soft lockouts clear only after their cause is resolved. Do not repeatedly reset a returning fault.
When should I arrange a repair?
Contact an ACV-qualified heating engineer if the code returns, the appliance remains locked out, a safety device has operated, or checks require internal access, test equipment or replacement parts.