The network power supply has failed
Every wall plate in the house is dark, including the backlights. Nothing on the network has power. This is the classic whole-system failure, and despite how it looks it is usually one module and a straightforward replacement.
The C-Bus network power supply has failed or lost its mains feed. Every unit on the network draws its low-voltage power from it, so when it stops, everything stops at once.
What this part actually does
C-Bus runs on a low-voltage network. A single cable carries both the data and the power that keeps every switch and sensor alive, and a dedicated power supply on the DIN rail feeds that network. It is a shared dependency: every unit needs it, so its failure is total and instant. That total quality is exactly what makes the diagnosis easy.
It is also the module most exposed to whatever comes down the mains, which is why it fails after storms more than anything else in the system. If your fault started with a blackout, that fits the pattern precisely.
This one is mains work. Stop here and book a licensed electrician. Switchboards, DIN-rail power supplies, dimmer and relay modules, and anything behind a faceplate are all live electrical work. There is no safe DIY version of this check.
Ask for an electrician with C-Bus accreditation if you can get one. A general electrician can safely isolate, test and replace hardware, but most cannot program the system afterwards, which is the half that makes your lights behave again.
Before assuming the module is dead
Two things to check from outside the board, because both are free and both are common. Has a circuit breaker or RCD tripped? The supply has its own mains feed, and if that has tripped the module is fine and simply unpowered. Resetting a breaker at the board is a normal householder action. If it trips straight back, stop and call an electrician; something is drawing fault current and repeatedly resetting it is not safe.
The second is subtler and is why an integrator will measure rather than assume: a dead short somewhere on the network can pull the bus down so hard that a perfectly healthy supply cannot lift it. The symptom is identical, total darkness on every plate, but the fault is in the cabling. That is covered in the network wiring fault page. It is the reason "just replace the power supply" is a guess rather than a diagnosis, and why a competent person tests before ordering parts.
What replacement involves
- Confirm it is the supply
- The bus voltage is measured before anything is ordered. This is the step that separates a real diagnosis from a parts swap, and it also catches the short-circuit case.
- Replace the module
- The supply is swapped on the rail. Licensed electrical work, and physically a small job.
- Check the burden
- A network has a finite power budget and every unit consumes part of it. If units were added over the years, the replacement is sized for what is actually connected now.
- Confirm everything returns
- Units repopulate the network once power is restored. Any that do not come back are noted, because they were probably already faulty behind the outage.
What this does not mean
It does not mean the system is dead, and it does not justify a replacement quote. Your switches, your modules, your programming and above all your cabling are untouched by a failed power supply. The lights being off everywhere is a symptom of a stopped heart, not a rotted body. Anyone using a total outage to argue for ripping the system out is either not testing or not being straight with you: see what replacement really costs.
Whole house dark since the storm?
This is one of the most common calls we get and usually one of the smaller jobs. Tell us when it started and whether anything at the switchboard has tripped, and we will tell you what we expect to find.