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One small switch on your switchboard can be the difference between a minor electrical fault and a fatal electric shock. That switch is the RCD — and not every Auckland home has one.
Here’s what you need to know.
What does an RCD safety switch actually do?
An RCD (Residual Current Device) monitors the flow of electricity through a circuit. The moment it detects a difference between the current going out and the current returning — even a difference as small as 30 milliamps — it cuts power in under 30 milliseconds.
That response time is fast enough to prevent electrocution. A standard fuse or circuit breaker only protects wiring — an RCD protects people.
Is an RCD required in New Zealand homes?
Yes — for new work. Under current New Zealand electrical regulations, all new circuits and any new electrical installation must include RCD protection. This has been the standard for some years, but it applies to new work, not existing wiring.
This means older Auckland homes — particularly those built before the mid-2000s — may have circuits that were installed before RCD protection was required, and never upgraded. If your switchboard still has old ceramic fuses or early-model circuit breakers with no RCD, your circuits likely aren’t protected.
How do you know if your home has RCD protection?
Open your switchboard and look for a switch labelled “RCD”, “Safety Switch”, or with a test button marked “T” or “Test”. Modern switchboards typically have one or more RCDs covering different circuit groups.
If you’re not sure what you’re looking at, the safest option is to have a licensed electrician check. It takes five minutes and removes the guesswork.
Why does my RCD keep tripping?
An RCD that trips occasionally is doing its job — it’s detected a fault. An RCD that trips constantly is telling you something needs attention.
Faulty appliance — the most frequent cause. Unplug appliances one at a time and reset the RCD after each to identify the culprit. Common offenders: older washing machines, kettles, dishwashers.
Moisture in wiring or fittings — moisture in outdoor power points, bathroom fittings, or around the switchboard can cause nuisance trips. If you suspect moisture is involved, call an electrician before resetting.
Deteriorating wiring — in older Auckland homes, insulation on wiring degrades over time. VIR and TRS cables (common in homes built before the 1960s) are particularly prone to this.
Nuisance tripping — occasionally RCDs trip without an obvious fault. If this happens repeatedly with no identifiable cause, the RCD unit itself may be ageing and due for replacement.
What to do if your RCD keeps tripping
- Unplug all appliances on the affected circuit
- Reset the RCD
- Plug appliances back in one at a time to isolate the fault
- If the RCD trips with nothing plugged in, or if you can’t identify a cause, call a licensed electrician
Don’t repeatedly reset an RCD that keeps tripping without investigating the cause. It’s tripping for a reason.
Does your Auckland home need an RCD upgrade?
If your switchboard is more than 15–20 years old and you’ve never had an electrical inspection, it’s worth having a licensed electrician check your RCD coverage. The cost of adding RCD protection to unprotected circuits is modest — particularly as part of a broader switchboard assessment.
At Northern Lights Lighting and Electrical, we assess switchboards across Auckland daily. If your home doesn’t have adequate RCD protection, we’ll tell you clearly what’s needed and what it costs.
Common questions
Can I test my RCD myself?
Yes. Press the “T” or “Test” button on the RCD — the power to that circuit should cut immediately. If it doesn’t, the RCD is faulty and needs replacing. Test every six months.
How many RCDs does a home need?
A modern switchboard typically groups circuits so that one or two RCDs cover the whole board. An electrician can advise on the right configuration for your home.
My RCD tripped and now I can’t reset it — what do I do?
If the RCD won’t reset, leave it in the off position and call a licensed electrician. Something on that circuit is still drawing current in a way that’s triggering the fault detection.
Not sure if your home has RCD protection?
