Ceramic Fuses vs Circuit Breakers: The Difference and Why It Matters

Ceramic fuses vs circuit breakers: what's the difference and does it matter?

A ceramic fuse and a circuit breaker do the same job, cutting the power when a circuit draws too much current, but a breaker does it faster, more consistently and resets with a switch instead of a piece of wire. Neither protects a person from electric shock; that's the safety switch, which fuse boards never have. If your board has ceramic fuses, it's the protection for people that's missing, not just the convenience.

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What a ceramic fuse does

A rewirable ceramic fuse holds a short length of thin wire rated to melt at a set current, 8, 16 or 20 amps typically. Draw more than that for long enough and the wire melts, breaking the circuit. To restore the power, someone pulls the holder, threads in a new piece of fuse wire of the right rating and pushes it back. It works. It's also slow to act on a moderate overload, it depends on the right wire being used every time, and it's a live board being handled by whoever's holding the torch.

What a circuit breaker does

A miniature circuit breaker is a switch with a thermal element for overloads and a magnetic element for short circuits. It trips faster and more predictably than fuse wire, it can't be "fixed" with the wrong rating, and it resets with a flick. It's been the standard on new switchboards for decades. On its own, though, it still only protects the cable. It won't notice 30 milliamps going through a person, because 30 milliamps is nothing to a 16-amp breaker.

What a safety switch does

A safety switch (RCD) compares the current going out with the current coming back. A difference of 30 milliamps, which is current escaping through a fault or a person, trips it in under 300 milliseconds. It's the device that turns a potentially fatal shock into a fright. Fuse boards don't have them, and older breaker boards often don't either. Modern boards combine the two functions in a single RCBO per circuit. Our guide on how often RCDs need testing covers keeping them working.

The comparison

	Ceramic fuse	Circuit breaker	Safety switch (RCD)
Protects the wiring from overload	Yes, slowly	Yes, fast	No
Protects a person from shock	No	No	Yes
Resets	New fuse wire, by hand	Flick the switch	Flick the switch
Can be fitted with the wrong rating	Easily	No	No
Typical board age	Pre-1990	1990s onward	Required on new circuits for years

Does it matter if the fuses still work?

For the wiring, a correctly wired ceramic fuse is adequate. For the people in the building, a fuse board offers nothing. Every year Australians are killed by electric shock in homes without RCD protection, mostly through faulty appliances, damaged leads and DIY work, and an RCD would have tripped in each case. That's the argument, and it's why we put this upgrade ahead of almost anything else on an older home. It's also a common condition of home insurance renewals and of leasing a property.

What replacing a fuse board involves

An assessment of the existing board, the mains and whether the backing panel contains asbestos.
A new board with a main switch, circuit breakers or RCBOs on every circuit, and labelling.
Power off for a few hours while the circuits are transferred and tested.
A Certificate of Compliance for the work, and a notification to SA Power Networks if the service connection is touched.

A residential board changeover is usually a 1-day job. See our switchboard upgrade service for what's included and the cost guide for the market ranges, including what an asbestos panel adds.

Need this done rather than read about? See switchboard upgrades or request a free quote.

Questions we get on this

Can I just add a safety switch to my fuse board?

Sometimes a single RCD can be added ahead of a fuse board as a stopgap, but a fault on any circuit then kills the whole house, and the fuses are still fuses. Almost always the sensible job is the full changeover, and the price difference is smaller than people expect.

Are ceramic fuses illegal?

No. Existing installations don't have to be upgraded unless work is done on them, at which point the new work must meet current standards, which in practice means RCD protection. We're electricians, not lawyers, so treat that as a general position and ask us about your specific board.

What's an RCBO?

A combined circuit breaker and safety switch in 1 device, 1 per circuit. It means a fault on the bathroom circuit trips only the bathroom, not half the house. It's what we fit as standard on new boards.