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Do I Need an RCD? NZ Home Electrical Safety Explained

RCDs — residual current devices, or “safety switches” — are the single most important electrical safety upgrade for an older home. Here's what they do and how to tell if yours are missing.

Published 2026-06-01 · Rotorua Electricians

What an RCD actually does

An RCD constantly monitors the electricity flowing out and back on a circuit. If it detects even a tiny imbalance — current leaking through a person or a fault — it cuts power in milliseconds. That speed is the difference between a scare and a serious electric shock. Ordinary fuses and old breakers don't do this.

How to tell if you have them

Open your switchboard and look for switches with a small “T” or “Test” button — those are RCDs. If your board only has ceramic fuses or plain breakers with no test buttons, you likely have no RCD protection on those circuits.

Does my home need them?

Modern NZ wiring standards require RCD protection on most circuits, and any new or altered circuits must have it. Older homes are often grandfathered — meaning it's legal until you do electrical work — but from a safety point of view, every home is far safer with RCDs. We strongly recommend them, especially where there are kids.

Getting RCDs fitted

RCDs are added as part of a switchboard upgrade, or sometimes retrofitted to an existing board if there's room. It's a quick, high-value safety job. We'll check your board and tell you honestly what it needs.

How we can help

FAQ

Quick answers

What's the difference between an RCD and a fuse?

A fuse/breaker protects wiring from overload and short circuit. An RCD protects people from electric shock by detecting earth leakage and cutting power in milliseconds. You want both.

Are RCDs a legal requirement in NZ?

Current standards require RCD protection on most circuits, and any new or altered circuit must have it. Older installs are often grandfathered until work is done.

Can I add RCDs without a full switchboard upgrade?

Sometimes, if the board has space. Often it's done as part of an upgrade. We'll assess and advise.

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