Baxi [E.02.47] fault codewhat it means and how to fix it

E.02.47 is the newer displays' version of the E83–E87 communication codes. The Combi 2 manual defines it as "connection to external device unsuccessful" with the cause "ELECTRICAL CONNECTION ERROR" and the remedy "possible cancellation, carry out the auto-detect function or re-enter the CN code"; the 200/400 Combi manual has the same description and "check wiring to external device", and pairs it with E02 48, "configuration to external device unsuccessful — check pairing to external, pair the devices". The external device is a Baxi room unit, a wired programmer on the boiler's bus, or an accessory board, and the boiler is reporting that something it was configured to talk to has stopped answering.

The Combi 2 has a family of A-codes for the same territory — A.02.36 and A.02.37 "functional device disconnected", A.02.45 "connection error", A.02.46 "device priority error", A.02.48 and A.02.49 — which are warnings the boiler runs through, and the manual's remedy for most of them is "carry out the auto-detect function", an installer menu that re-discovers what is connected. The permanent E.02.47 needs the RESET button, one second on a Combi 2 and at least three seconds on a 200/400, but the reset does nothing until the missing device is back or the boiler has been told to stop expecting it.

For the householder the useful checks are outside the boiler: the control's display and batteries, whether it has been unplugged or moved, and whether the code appeared the day a new thermostat was fitted. The last case is the common one, and the fix is in the installer's hands — either the pairing was not completed or a control was wired to the bus terminals that should have gone on the switched-live pair. The Combi 2 manual adds one line worth knowing: when a room unit or control unit is connected, "the code 254 is always shown in the event of a fault" on the control, and the real code is on the boiler's own display.

1. 1

   Check the room control: replace flat batteries, refit it to its wall plate, and see whether it shows a code of its own. On a Combi 2 the control may show 254; the real code is on the boiler.

2. 2

   If the code appeared after a new thermostat was installed, tell the installer. The pairing or the terminals are almost certainly the cause, and the boiler wiring cover is not for you to open.

3. 3

   Once the control is back, reset: one second on a Combi 2, at least three seconds on a 200 or 400 Combi. If E.02.47 stays, an engineer will run the auto-detect function or check the bus wiring.