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critical Worcester
Error Code A27
Unable to communicate with the boiler’s EMS bus system due to incompatibility or other causes.
? What Causes This
Configuration issues, connection errors between RF control units and EMS-compatible boilers.
✓ How to Fix It
Check that connections are properly established according to installation manuals; replace faulty components like interface cables if necessary.
Source: page 19 of the official manual
From the manual
This error code appears in:
Worcester Greenstar Comfort II RF