A whole room or group of lights is dead
A whole area has gone dark or unresponsive while switches elsewhere in the house behave normally. The pattern of what died together is the clue, and it usually points at one module or one circuit.
C-Bus does not wire lights the way a conventional house does. The circuits run back to output modules, usually rows of dimmers and relays on a DIN rail inside an enclosure, and each module drives several circuits from its own channels. When an entire area drops out at once, the most common explanation is that one module, or one electrical circuit feeding it, has stopped. Individual switches almost never fail in a group.
Nothing on this page asks you to take anything apart. Every check here is done by looking, or by pressing buttons that are already on the outside of a wall plate. Opening the hinged door of your switchboard to see the breakers is normal and fine. Removing the panel behind them is not, and neither is unscrewing a wall plate or lifting the cover off an enclosure.
In Australia it is illegal to work on fixed wiring without an electrical licence, and the reason is not paperwork: the terminals behind a C-Bus wall plate can be sitting at mains voltage. Anything past the faceplate is a job for a licensed electrician, ideally one with C-Bus accreditation.
Does the switch for the dead area still show signs of life?
Press a key on a plate that controls the dead lights and watch its indicator LED.
- The switch LEDs light up and change, the lights do nothingThe switch is sending. The module that should be answering is not, or its channels have failed. The most likely single fault behind a dead room.
- Nothing at all in that area has power, including things that are not on C-BusIf a power point or a non-C-Bus light in the same area is also dead, this is a tripped breaker or a mains fault, and it is not a C-Bus problem at all.
- The switches in that area are completely dark tooIf the wall plates themselves have gone dark, that part of the network has lost its power or its data connection.
- Some lights in the room work, others in the same group do notA partial group points at the lamps, drivers or one channel, rather than the module as a whole.
Check the switchboard first, from the outside
Before anything else, open the hinged door on the front of your switchboard and look at the row of breakers. A tripped one sits visibly out of line with its neighbours, and resetting it is a normal householder action. If it trips straight back, stop: that is a real electrical fault and a job for a licensed electrician, not a C-Bus question. Do not keep resetting it, and do not remove the panel behind the breakers.
Why one module can take out a whole area
An eight-channel or twelve-channel dimmer commonly feeds one wing of a house. If that unit loses its supply, fails internally, or has been switched to a local override at some point, everything it drives goes with it. That is why "half the house is dead" sounds catastrophic and usually is not: the failure is one replaceable module on a rail, and the wiring around it is untouched.