The rating and the curve
A breaker marked C16 has a C curve and a 16 amp rating. Household circuits commonly use ratings such as 10, 16, 20 and 32 amps, with lighting at the lower end and ovens, cooktops and larger air conditioners at the higher end.
The curve letter is about starting surges. Motors and some LED drivers draw a burst of current for a moment as they switch on. A B curve trips on a smaller burst, a C curve allows more, and a D curve more again for heavy motor loads. A smaller figure in a box, often with kA, is the fault current the breaker can safely interrupt. It matters to the electrician choosing the breaker rather than to you.
Markings on safety switches and RCBOs
Energy Safe Victoria says a safety switch always has a test button and 30mA printed on it. That figure is the leakage current it is designed to trip at, far below anything that would trip a breaker. An RCBO shows both, for example C16 alongside 30mA.
You may also see a type symbol. Energy Safe Victoria says Type AC devices must no longer be installed, even as like-for-like replacements, although existing ones that were installed, tested and certified before 1 May 2023 don't have to be replaced.
Why a bigger breaker isn't a fix
The rating is chosen to protect the cable on that circuit. Swap a 16 amp breaker for a 32 amp one and the tripping stops, but the cable can now carry enough current to overheat inside the wall before anything switches off. If a breaker trips often, the answer is finding the cause: too much on one circuit, a faulty appliance or a wiring fault. Changing breakers is electrical work, and Energy Safe Victoria's message is that electrical work isn't a DIY job, even a small one.
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Related questions
- How do I tell which switch has tripped on my switchboard?Open the switchboard door and look along the rows of switches.
- What's the difference between a safety switch and a circuit breaker?A safety switch protects people.
- Why does my main switch trip?Many main switches are only isolators and can't trip on their own.
- My meter box door is broken or won't close. Who fixes it?The property owner.
Sources for this answer
3 sources, with the date each was checked
- 1.Energy Safe Victoria: monitors the flow of electricity through a circuit detects a problem that may pose a risk to personal safety turns the power off within 0.03 of a second always has a test button and '30ma' printed on them. Accessed 30 September 2026.
- 2.Energy Safe Victoria: Type AC RCDs must not be installed in Australia. This includes like for like replacement. We recommend that electrical contractors advise customers of the new requirements. However, it is not mandatory to replace… Accessed 30 September 2026.
- 3.Energy Safe Victoria: Electrical work isn’t a DIY job, even for small jobs such as changing power points or light switches. Accessed 30 September 2026.
General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.