The short answer
Ceramic rewireable fuses and circuit breakers do the same basic job: they cut a circuit off when too much current flows, so the cable doesn't overheat. A fuse does it by a piece of wire melting, and has to be rewired or replaced afterwards. A circuit breaker switches off and can be reset. The real difference for your family is what comes with each: an old ceramic fuse board almost always has no safety switches, while a modern board with breakers can have an RCBO on every circuit, which protects against electric shock as well as overload. If you still have ceramic fuses, it is a good reason to get your board checked.
How a ceramic fuse works
A rewireable fuse is a ceramic carrier that plugs into a holder on the switchboard. A length of fuse wire runs through it. When a circuit draws more current than the wire is rated for, the wire heats up and melts, breaking the circuit. To get the power back, the carrier has to be pulled out and rewired with the right size of wire.
That design has a few weak points:
- The wrong wire can go in. Fuse wire comes in different ratings and it is easy for a heavier wire to end up in a carrier over the years. Then the fuse no longer protects the cable it is meant to protect.
- They only protect against overload and short circuits. A fuse doesn't detect current leaking to earth through a person, so it gives no protection against electric shock.
- Old carriers can contain asbestos. The NSW Government's asbestos website says old fuse carriers and some fuses (Federal brand, for example) may contain friable asbestos. Friable asbestos legally needs a licensed removalist in NSW.
- They are usually on old boards. Ceramic fuses tend to go with old wiring and black bituminous backing boards made before 1987, which may also contain asbestos.
How a circuit breaker works
A miniature circuit breaker (MCB) is a switch that trips off automatically when a circuit is overloaded or short-circuited. Once the cause is fixed, you flick it back on. There is no wire to replace and no way to "upsize" it by accident.
On its own, a circuit breaker still doesn't protect against electric shock. That is the job of a safety switch, or RCD, which cuts power quickly when it detects current leaking to earth. An RCBO combines an RCD and a circuit breaker in one device, protecting a single circuit against overload, short circuit and earth leakage. Our RCD vs RCBO guide explains the difference.
Side by side
| Ceramic rewireable fuse | Circuit breaker (MCB) | RCBO | |
|---|---|---|---|
| Protects cable from overload | Yes | Yes | Yes |
| Protects against electric shock | No | No | Yes (30 mA) |
| After it operates | Rewire or replace the fuse | Reset the switch | Reset the switch |
| Risk of the wrong rating fitted | Yes, with fuse wire | Low | Low |
| Asbestos risk in old parts | Possible in old carriers | No | No |
Is it illegal to still have ceramic fuses?
We are not aware of any general NSW law that forces you to replace a working fuse board just because of its age. What the rules do say:
- If a final subcircuit is altered or added, that circuit must get 30 mA RCD protection at the switchboard. This is the AS/NZS 3000:2018 position set out in the ERAC advisory note that all Australian regulators endorse. In practice, on a fuse board, there may be no room to add one cleanly.
- If the switchboard is replaced for any reason, every applicable final subcircuit from it must have RCD protection.
- Domestic installations need at least two RCDs, with no more than three final subcircuits on any one RCD.
So, while the fuses themselves aren't banned, most jobs that touch an old fuse board end up needing a new one.
Don't rewire fuses yourself
The NSW Government says DIY electrical work is "dangerous and illegal", and that homeowners shouldn't do electrical maintenance beyond changing a light globe. On top of that, old fuse carriers may contain asbestos. If a fuse blows, don't try to rewire it. Unplug or switch off what was running on that circuit and call a licensed electrician. If fuses keep blowing, there is an overload or a fault that needs fault finding.
What upgrading looks like
When we replace a fuse board, every circuit gets its own RCBO and the board gets a new main switch and a new enclosure. Each circuit is tested before it is put back into service, and you get a Certificate of Compliance for Electrical Work (CCEW), lodged through the Building Commission NSW eCert portal.
The cost depends mostly on the number of circuits, since each one gets its own RCBO, plus the main switch, whether a new enclosure is needed, and testing and the certificate. See switchboard upgrade cost for what goes into the price, or use the instant estimate for your board.
If your board might contain asbestos, read asbestos switchboards in NSW first. Asbestos work is quoted separately, and the NSW asbestos website advises using a licensed asbestos assessor and removalist.
Common questions
Are ceramic fuses safe?
They protect cables from overload when they have the right wire in them, but they don't protect people from electric shock, and old carriers may contain asbestos. That is why we suggest getting a fuse board checked by a licensed electrician.
Can I just swap my fuses for circuit breakers?
Swapping fuses for plug-in breakers still leaves the board without safety switches and doesn't deal with an old backing board. Changing protective devices is electrical work, so a licensed electrician needs to look at it. In most cases a full switchboard upgrade with an RCBO on each circuit is the sensible option.
Why do my fuses keep blowing?
Usually because the circuit is overloaded (too many appliances running at once) or there is a fault in the wiring or an appliance. Don't put heavier fuse wire in. Get the cause found by a licensed electrician.
Do circuit breakers trip more often than fuses?
A breaker trips for the same reasons a fuse blows. With RCBOs, a circuit will also trip if current is leaking to earth, which is exactly the kind of fault a fuse can't detect. If one keeps tripping, see safety switch keeps tripping.