Commonly Asked Questions: Why is my RCD tripping?

Or, rather, why is my power cutting out all of a sudden?

These are two questions we get asked a lot as licensed electricians. Even if you haven’t heard of a residual current device before, it’s extremely likely that you have one within your home. So here, we’ll explain the basics behind this essential home-safety feature: the residual current device (or RCD for short). We’ll explain how to understand what it’s telling you, and what steps to take as a result.

About your Residual Current Device (RCD)

An RCD (Residual Current Device) is also known as a “safety switch”: it’s here to protect you against a number of dangerous electrical hazards in your home and business. You’ll find it inside your home’s fuse box, where it will likely be labelled.

Most houses in Australia will have an RCD, but not all. It’s mandatory for all new builds in Australia to have an RCD fitted on all of your final sub-circuits. In most states and territories around the country, you must install an RCD before selling or renting a home. And there’s a good reason that this device is required: it can (and does) save lives!

Why are RCDs so important?

An RCD is constantly monitoring the current that’s flowing through a circuit. If it detects electricity flowing into the earth at a dangerous level, it shuts down the circuit (or ‘trips’) at a rapid speed. This is an important function, as electricity flowing into the earth often means it’s leaking into something else, like a human being, which can cause a fatal electrical shock.

It can also help to prevent an electrical fire that may be caused by faulty wiring or faulty appliances.

What’s the difference between an RCD (safety switch) and a circuit breaker?

An RCD is designed to be more sensitive than conventional circuit breakers and fuses, and can shut off the supply at a much faster rate. Electrical shocks can cause death or serious injury in under a second – and that’s why the ultra-fast tripping of your RCD can be lifesaving. Generally, to be considered compliant in Australia, your RCD will need to trip within 300 milliseconds (0.3 seconds).

Common causes of RCD tripping

If your RCD switch has cut off the electrical supply, there are a number of possible explanations. Here, we’ll break down some of the most common reasons.

1. Faulty appliances

If you find your RCD tripping on a regular basis, it’s important to rule out faulty appliances. It’s not always obvious which appliance is responsible, but the most common suspects include appliances with heating elements or those most at risk of water damage. Appliances with heating elements – like kettles and toasters – often trip RCDs when the insulation within their heating elements breaks down and causes the current leakage into their metal outer components.

Appliances like dishwashers and washing machines are also common RCD-tripping culprits, as they bring water and electrical currents in close proximity with one another. Water is an excellent conductor of electricity, so when electrical components come in contact with even small amounts of moisture, your RCD may detect this leakage current and trip.

What to do if you suspect faulty appliances are causing RCD tripping

Sometimes, it’s not immediately obvious which appliance is causing RCD tripping. Damage or wear to an item might not be easy to see from the outside. You can troubleshoot by turning all appliances off and resetting the RCD, turning one appliance on at a time to find the problem through a process of elimination.

If you’re not confident doing this yourself or don’t have the time, a licensed electrician can easily determine this for you. The faulty electrical equipment will need to be repaired (by a licensed professional) or replaced; it’s too dangerous to use in its current state.

2. Overloaded circuits

Sometimes, there’s simply too much demand on a circuit! If multiple devices or high-powered appliances are connected to the same circuit and being used at once, this could very well be why your RCD keeps tripping.

What to do if an overloaded circuit is causing RCD tripping

The solution to overloaded circuits is generally pretty simple – spread your high-powered appliances across multiple power outlets. Avoid the old habit of plugging one powerboard into another, and try to understand how much power each appliance uses – it might be more than you think!

3. Damaged wiring

The wiring in the system itself – not just the appliances connected to it – may also be faulty. Like any part of your home, wiring can – of course – become less safe and less effective as it ages. It could be moisture ingress or even damage from pests like rodents. The damaged wiring will cause earth leakage and trigger RCD tripping.

What to do if damaged wiring is causing RCD tripping

Do not attempt to fix damaged wiring yourself! Call a licensed electrician – they will be able to diagnose the problem, remove the risk associated with it, and help you get your electrical systems up and running safely. A qualified electrician is the only person you should trust with repairing faulty wiring or any electrical wiring in your home.

4. Faulty RCD

The final explanation for RCD tripping that we’ll discuss here is a problem with the RCD itself. This also highlights the importance of testing your RCD – you or a licensed electrician should be doing this on a regular basis. In your fuse box, you’ll find an RCD test button. If you press this and the RCD does not trip, it indicates a fault. However, your RCD could still be faulty, even if it does trip: it’s best to call in the help of a qualified electrician to determine the root cause.

What to do if a faulty RCD is causing frequent RCD tripping

If your RCD keeps tripping, and a qualified electrician determines that the RCD itself is the cause, they will be able to replace it for you.

It’s vitally important that you have it replaced as soon as possible: RCDs serve an incredibly important function within your home, preventing potentially lethal electric shocks.

A final word on RCDs

While it’s entirely possible to use a process of elimination to find what’s causing frequent RCD tripping, if you have concerns that it’s more than just an overloaded circuit or an ageing toaster, it’s a good idea to call in the professionals. At Gimpel Electrics, we’re dedicated to high-quality craftsmanship that results in safe, efficient homes. We’re here to help you navigate all kinds of electrical safety challenges, big and small, so that you can feel safe and connected in your home or business.

We’re always happy to chatabout  electrical safety – don’t hesitate to get in touch for a site visit or free quote.