Just an update.
Apparently, according to a Worcester Bosch engineer the original installer wired the EMS low voltage bus to the mains by mistake and burnt out the low voltage side of the board.
The rest of the board is still working fine so the boiler is working, the board is now going to be replaced.
Apparently, according to a Worcester Bosch engineer the original installer wired the EMS low voltage bus to the mains by mistake and burnt out the low voltage side of the board.
The rest of the board is still working fine so the boiler is working, the board is now going to be replaced.