Cause of error code A05

Internal error safety relay

- Safety relay is not reacting correctly to software commands.

Solution for error code A05

- If persistent locking errors, A05 occur, systematically disconnect all wires not supplied by the factory with the exception of the power supply (CH T’Stat, DHW T’Stat, LWCO, Pumps, etc.). If the error code goes away, determine which circuit may be introducing electrical noise or feedback. 
- If the error persists after all these wires are disconnected, contact your PB Heat representative. 
- If this error occurs after replacing a control, contact your PB Heat representative.