Upgrading Your Old Ceramic Fuses

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Here is a question from one of our customers William who is looking to do some handyman work on the fuses in his home.

Q: I want to change my old fuses to circuit breakers. The old fuses are 36A, 30A, 16A and 20A. I can buy the 16A and the 20A, but Bunnings don’t have the 36A or the 30A. They have a 40A and 32A. Also I put in a 3600W hot water service what fuse should be used in it?

A: Firstly, thanks so much for your email. We are more than happy to help you out with some advice.
You mentioned that you were sourcing the new circuit breakers from Bunnings and doing the work yourself. While companies like Bunnings make it so easy these days to do a lot of renovation, repairs and upgrades ourselves, when it comes to your homes electrics we really do recommend that you get an expert in to do the work for you. Below is some information that can be found around the web which explains why:

The Types of Circuit Protection for your home

Ceramic Fuses

Ceramic fuses (SERF-semi-enclosed re-wireable fuses) are old school forms of electrical protection for a home. These are the sort where you run fuse wire around some screws (usually in the dark while holding a torch) before plugging them back into your fuse box. They provide short-circuit and overload protection, and provide limited protection to your property and no protection from electric shocks.

Plugin Circuit Breakers

The next development in fuses technology was a replacement plug in (plugin MCB) circuit breaker that can be inserted into the old porcelain fuse base. These were a step forward from juggling fuse wire in the dark, but still only have the same protection as fuses. They are a risk, because handymen are able to swap them around with the wrong ratings, which can potentially overload cabling which is very dangerous.

Hardwired Circuit Breakers

The first hardwired circuit breakers (MCB’s) were a step up for safety in that they couldn’t be swapped around by over enthusiastic DIYers. Although quicker acting than fuses or plug in breakers, they still only provide short circuit and overload protection. These fuses should be used in conjunction with a Residual Current Device (RCD). RCD’s act as a circuit breaker as well as a safety switch. These are highly recommended for the safety of yourself and anyone else within your home.

Circuit Breakers

Residual Current Device (RCD)

Safety switches or RCD’s were the next huge step forward, as they not only protected a number of circuits but they also protected against electric shock for the first time. Generally, one safety switch is linked to a number of circuit breakers. The main drawback of this was that when they are tripped, they take out supply to an entire house.

As you can see, there are benefits and shortcomings to all of the solutions above. So what is the solution?

Electrical Part

Combination Safety Switches/Circuit Breakers

The most modern type of switches are combination safety switches and circuit breakers (RCBO’s). These protect single circuits from shorts, overloads and electric shocks. This means any problem is confined to that one circuit and will not take out the circuits for the rest of your house. The other advantage is that nuisance trips become a virtual thing of the past as each circuit has its own “earth fault” limit as opposed to having one safety switch protecting numerous circuits.


If your house has ceramic or plug in fuses, then you really need your fusebox upgraded to the current standards, which must be completed by a licensed electrician. If you have older style circuit breakers or a number of breakers connected to a safety switch, then it pays to replace them with combination switches (RCBO’s) for greater safety and peace of mind, and to reduce nuisance tripping.

You can read more here about when you should upgrade your switchboard: “How much does it cost to replace a switchboard

The same advice also goes for your hot water system. As this is usually the highest draw of current for any home, it’s best to have it done right.

Give us a call at The Plumbing & Electrical Doctor and one of our trained, licensed electricians can come out to give you the right advice. We serve areas in Newcastle, Canberra, Hunter Valley, Lake Macquarie and Port Stephens.