What you can safely check yourself
There is a genuine list of useful things you can do without any risk, and there is a hard line you do not cross. This page draws both clearly, because most C-Bus advice online is vague about exactly where the line sits.
The line, stated once
Nothing behind a faceplate or a panel. Ever. Do not unscrew a wall plate, remove the panel inside your switchboard, or take the cover off an enclosure, whatever you have seen on the internet.
The one thing that is normal: opening the hinged door on the front of your switchboard so you can see and operate the circuit breakers. Householders are expected to do that. The flat panel behind the breakers is the boundary, and it stays on.
In Australia, work on fixed electrical wiring requires an electrical licence. This is not bureaucratic caution: the terminals behind a C-Bus wall plate can sit at mains voltage, and the enclosure holding your dimmers is a live switchboard. The C-Bus network itself is extra low voltage, but it shares space with mains, and you cannot tell which is which by looking.
What you can safely do
- Look at the indicator LEDs
- Free, safe, and the single most diagnostic thing available to you. See the guide to reading them.
- Press keys and record what happens
- Walk the house, press everything, write down what works and what does not. This list is worth real money at quoting time.
- Look at the breakers in your switchboard
- Open the hinged door on the front and look at the row of switches. A tripped breaker or RCD sits visibly out of line with its neighbours. The panel behind the breakers stays on.
- Reset a tripped breaker once
- Fine, if it holds. If it trips straight back, stop and call an electrician. Do not keep resetting it.
- Switch a plug-in device off and on
- If a controller, touchscreen or PC runs from a power point, switching it off at the point, waiting, and switching it back on is a safe restart.
- Photograph the enclosure from outside
- Photograph the closed enclosure and its surroundings. Useful for quoting. Do not open it to get a better shot.
- Check the lamps
- Note which lights are LED and which are halogen, and whether anyone changed them recently. This one fact resolves a lot of dimmer complaints.
- Search for the project file
- The most valuable hour you can spend. Old computers, USB sticks, the house documents folder, the previous owner.
What needs a licensed electrician
- Anything behind a faceplate
- Removing, testing or replacing a wall switch unit.
- Anything in the switchboard or enclosure
- Dimmers, relays, the network power supply, and every connection in there.
- Any measurement of the bus
- Testing network voltage means being inside an enclosure. It is a normal part of a proper diagnosis, and it is their job, not yours.
- Any breaker that will not hold
- Repeated tripping means fault current. Leave it off.
- Anything after a burning smell, heat or discolouration
- Stop, isolate if you can do so from outside, and call someone today.
About unit toggle buttons
C-Bus output modules have small buttons on their front faces that switch a channel locally, and you will find advice online telling you to press them. Be careful with that advice. If reaching the button means opening a switchboard door, removing a cover, or getting anywhere near a terminal, it is electrician's territory and not worth the risk for a diagnostic step someone else can do in seconds.
The reason those buttons matter to you is different: they let an electrician prove, in one press, whether a dead circuit is the module or the programming. If the light comes on from the module but not from the wall switch, the wiring and the lamp are fine and the problem is on the control side. Worth knowing so you understand what they are doing, and worth asking them to try. Not worth doing yourself.
Why the free checks are worth doing anyway
Because they change what you are buying. A call-out that begins with "the lights are playing up" starts with an hour of someone working out what you meant. A call-out that begins with a room-by-room list of what works, what does not, which plates are lit, when it started and what changed just before, starts with the actual diagnosis. On a system nobody has documentation for, that difference is significant, and it is entirely within your control.
When you have your list, take it to the fault diagnoser.