Arc Fault Detection: Why a Standard Safety Switch Won't Stop an Arc Fault

​Many homeowners assume that once a safety switch is installed, their home is fully protected against electrical fire risk. That assumption misses a real gap. Arc fault detection Auckland homes increasingly rely on covers a specific danger that safety switches were never designed to catch. This guide explains that gap clearly, and what closes it properly.

What Is an Arc Fault

An arc fault is a dangerous electrical discharge that occurs when electricity jumps across a gap in a damaged or poorly connected circuit, rather than flowing through it as intended.
How an Arc Fault Happens
Arc faults typically develop from damaged insulation, loose connections, or wiring that's been pinched, aged, or nicked during past work. Each of these creates a small gap where electricity can arc across, generating intense, localised heat.
Why Arc Faults Are Hard to Notice
Unlike a tripped circuit or a blown fuse, an arc fault often produces no obvious symptom at first. There's no immediate power loss, no clear warning sign, just heat quietly building at the point of the fault until damage or fire risk becomes serious.

What a Standard Safety Switch Actually Protects Against

Understanding safety switch vs arc fault detection starts with knowing exactly what a safety switch is built to catch, and what it isn't.
How a Safety Switch (RCD) Works
A residual current device, or RCD, monitors current flowing through a circuit and compares what goes out against what comes back. If current is leaking to earth, typically through a person or a fault, the RCD cuts power almost instantly, primarily to prevent electric shock.
What a Safety Switch Doesn't Detect
An RCD isn't designed to detect arcing within a circuit that doesn't involve current leaking to earth. This is the exact gap arc faults exploit, since an arcing connection can generate serious heat without ever triggering an RCD to trip.

What Is an AFDD and How It Closes the Gap

An AFDD, or arc fault detection device, is built specifically to catch what an RCD misses.
How an AFDD Detects Arc Faults
An AFDD continuously monitors the electrical waveform passing through a circuit, watching for the specific irregular signature that arcing produces. When that pattern is detected, the AFDD cuts power to the circuit before heat has a chance to build into a serious hazard.
AFDD vs RCD: Different Jobs, Both Needed
An AFDD and an RCD aren't competing devices, they protect against entirely different risks. An RCD guards against electric shock from current leaking to earth. An AFDD guards against fire risk from arcing within the wiring itself. A genuinely well-protected home has both working together.

Why Arc Faults Are a Genuine Fire Risk

Undetected arcing generates concentrated heat at a single point in a wall cavity or behind a fitting, often for extended periods before anyone notices anything wrong. Over time, that heat can ignite surrounding insulation, timber framing, or dust buildup, turning a hidden electrical fault into a house fire. Older wiring and ageing switchboards carry more of this risk, simply because insulation degrades and connections loosen over the decades a system has been in use.

Signs Your Home May Be at Risk

A few warning signs are worth checking for:

• Discoloured or warm power points and switches
• Flickering lights not linked to any known appliance
• A faint burning smell with no obvious source
• Older wiring or a switchboard that hasn't been assessed in years
• Frequent, unexplained circuit issues

Any of these signs are worth having assessed properly, since arc faults rarely announce themselves clearly before becoming dangerous.

Arc Fault Protection and Switchboard Upgrades

​AFDDs are usually installed as part of a broader switchboard upgrade, rather than fitted as a standalone add-on to an existing board. This makes sense practically, since a switchboard upgrade already involves assessing circuit capacity and safety switch coverage, and adding arc fault protection at the same time avoids a second round of work later. Homes already showing signs of surge-related issues, covered in our guide on power surges in Auckland homes, are often good candidates for this kind of combined upgrade.

Arc Fault Protection in Switchgear Upgrades for Larger Properties

The same principle applies at a larger scale for commercial buildings and bigger residential properties. A switchgear upgrade handles higher electrical loads and more complex circuit arrangements, and arc fault detection fits naturally into that broader capacity and safety planning. Properties that have recently added high-draw equipment, similar to the switchboard capacity issues covered in our piece on EV chargers and gate motors, are worth assessing for arc fault protection at the same time as any capacity upgrade.

Is Arc Fault Detection Required in New Zealand

Arc fault detection isn't universally mandated across every property in New Zealand, but it's increasingly recommended, and expected in certain higher-risk installations, as awareness of arc-related fire risk grows. Rather than guessing where a specific property stands, it's worth raising arc fault protection directly during any switchboard or switchgear assessment, so the right level of protection is confirmed rather than assumed.
Final Thoughts
A safety switch and an AFDD protect against two different risks, and a genuinely well-protected home needs both working together, not just one or the other. Arc fault protection is best addressed as part of a proper switchboard or switchgear upgrade, rather than treated as a separate afterthought. Strike Electrical assesses Auckland homes and businesses for arc fault risk and installs AFDD protection as part of switchboard and switchgear upgrades, giving properties genuine, complete protection against both shock and fire risk.