A05 Drainage alarm warn that during boiler flush water was detected. 
As consequence unit deactivate the boiler and show the message. 
This message does not necessarily require the intervention of a technician; the causes of the failure can be external.
Description
During the boiler flushing cycle (drain wash or calout) drain sensor detect water after a timeout period. Issue can be due to scale deposit on drain probe to the drain valve or blocked drain.
Reset
Error reset automatically when a flush cycle is properly completed. 
Start the cycle from menu boiler/drain flush. 
Warning: a cycle done fron function test do not reset the error.
Checks
Perform following checks: 
- Check drain valve 
- Check drain probe.
