Ceramic fuses vs circuit breakers

Walk into the meter box of an older brick or fibro home in the Illawarra and there is a good chance you will find a row of white ceramic fuse holders. In newer homes you will see a neat row of switches instead. Both are there to protect your wiring, but the way they do it, and how well they suit a modern home, is quite different.

How a ceramic fuse works

A rewireable fuse is a ceramic carrier holding a short length of fuse wire. When too much current flows, the wire heats up and melts, breaking the circuit. To restore power, you pull out the carrier, replace the wire and push it back in.

It is a simple idea and it worked well for the loads homes had decades ago. The trouble lies in the details.

• Fuse wire takes time to heat and melt, so the response is slower than a modern breaker
• It is easy to rewire with thicker wire than intended, which removes the protection
• Replacing fuse wire in the dark with the board live is not safe
• Fuses protect cables from overload but do nothing to protect people from shock

How a circuit breaker works

A circuit breaker is a switch that trips automatically when current exceeds its rating. It responds to sustained overloads and reacts very quickly to short circuits. To reset it, you fix the cause and flick the switch back on. No wire, no tools.

Breakers come in fixed ratings matched to the cable they protect, so there is no temptation to "upsize" the protection with heavier wire.

Where safety switches fit in

Here is the important part. Neither a fuse nor a standard circuit breaker protects you from electric shock. That is the job of a safety switch, or residual current device. It watches for current leaking to earth, which can happen when someone touches a live part, and cuts the power in a fraction of a second.

Modern boards combine circuit breakers with safety switches, or use combined units called RCBOs that do both jobs for each circuit. A ceramic fuse board usually has no safety switch at all. Our guide what is an RCD and how many do I need goes deeper.

Can you just swap the fuses for breakers

There are plug-in breakers designed to replace some fuse carriers, but they do not add shock protection and they do not address the age of the board, the backing panel or the wiring behind it. In most older homes, the sensible path is a proper switchboard upgrade, where the old board is replaced with a new enclosure, modern breakers and safety switches.

What about the wiring

A board full of ceramic fuses often means the cabling is of a similar age. During an upgrade we test each circuit. Most of the time the wiring is serviceable. Sometimes we find rubber insulated cable or damaged sections that need replacing. If so, we will explain what we found and your options, including partial or full rewiring.

A quick comparison

• Ceramic fuse: slow, rewireable, easy to misuse, no shock protection
• Circuit breaker: fast, resettable, fixed rating, no shock protection
• Safety switch: detects earth leakage and protects people
• RCBO: breaker and safety switch in one, per circuit

Should you upgrade

If your home still runs on ceramic fuses, an upgrade is one of the most worthwhile electrical jobs you can do. It is especially worth doing before a renovation, before adding a pool or sauna, or if you have young children in the house.

Send a photo of your board to Kalani on 0424 400 346, by call or text, and we will tell you what we see.