Why Is My RCD Tripping?

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RCD tripping is caused by earth leakage — most often a faulty appliance, moisture inside a fitting or cable, degraded wiring insulation, or cumulative leakage across shared circuits. If tripping repeats or returns after resetting, you have an active fault that can cause electrocution or fire; call 0433 462 902 or book a diagnostic before resetting again. Every trip must be treated as real: RCDs are the single most important shock-protection device in your switchboard.

Sydney Electrical Service handles RCD diagnostics 24/7 across every Sydney suburb — from older Federation cottages in Marrickville and Annandale to high-rise strata in Pyrmont and Zetland. Northern Beaches outdoor entertaining areas face accelerated insulation breakdown from salt air and weather, making them a frequent source of hard-to-trace earth leakage.

What This Fault Means

An RCD (Residual Current Device) continuously compares the current flowing into a circuit on the active conductor with the current returning on the neutral conductor. In a healthy circuit, those values are within a few milliamps of each other. When current “goes missing” — leaking to earth through faulty insulation, water, or a person — the RCD opens within 30 ms at a threshold of typically 30 mA. That speed is what stops a fatal shock.

There are several types of RCD you may encounter in Sydney homes:

Type AC — the legacy domestic standard, detects sinusoidal earth leakage
Type A — required for circuits feeding modern electronics, EV chargers, induction cooktops
Type B — required for many three-phase commercial loads and DC-component circuits
RCBO — combined RCD + circuit breaker; one device per circuit, the modern best practice

If your switchboard is still using a single bank-style RCD covering many circuits, a fault on any one of them takes the whole bank down — one of the most common reasons we recommend upgrading to per-circuit RCBOs.

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Common Causes

A faulty appliance with cracked or aged insulation — kettles, toasters, irons, hair dryers, vacuum cleaners
Water entering an outdoor power point, garden light, or pool/spa equipment
A leaking shower, bath, or laundry where waterproofing has failed and damp has reached cabling
Damaged cable in the roof space — possums and rats are notorious in Sydney's older suburbs
Cumulative low-level leakage from many appliances stacked on the same RCD bank (the so-called "death by a thousand cuts")
Aged ceiling-mounted heaters, electric blankets, or pool blanket motors
Failed LED downlight drivers or unbranded transformers
Surge damage to appliance internals after Sydney summer storms
Solar PV inverter DC injection, particularly in older inverters lacking proper Type B protection
A worn or end-of-life RCD that misreads its own internal balance
A pinched cable behind a recently hung shelf, mirror, or TV bracket

Is It Dangerous?

Yes — every trip is the device telling you something is leaking. The danger you should not ignore includes:

Red flags — call immediately if you see any of these:

A tingle, prickle, or buzz when you touch a tap, appliance, or shower fitting
A burning, fishy, or "electrical" smell anywhere on the affected circuit
Hot or discoloured power points on the affected circuit
An RCD that holds for a few seconds then trips — strongly suggests a real, active leakage
An RCD that won't trip when its TEST button is pressed — the device itself has failed

What to Do Right Now

Open the switchboard. Find the tripped RCD (the toggle will be in the middle position, or fully OFF).
Switch every breaker downstream of that RCD to OFF.
Reset the RCD to ON. It should now hold because no circuits are live.
Switch breakers back on one at a time with a 30-second pause between each.
The breaker that re-trips the RCD is the faulty circuit.
Unplug everything on that circuit and try again.
If the RCD holds, plug appliances back in one at a time to find the offender.
If it doesn't hold with everything unplugged, the fault is in the fixed wiring or a hardwired appliance — leave it OFF and call us.

When You Must Call a Licensed Electrician

We strongly recommend a licensed electrician any time:

The RCD won’t reset with all circuits and appliances disconnected
You feel a tingle from a tap, sink, or appliance
The trip occurs during or right after rain or storms
You can smell burning anywhere in the house
The RCD test button does not trip the device
The home has aluminium wiring or a switchboard older than 1995
Multiple units in your strata building lose power at once
The trip is repeated and you cannot identify a single appliance cause

We are licensed Level 2 ASP contractors operating across all of Sydney, which means we can attend, diagnose, repair, and certify the work in a single visit — including consumer-mains, switchboard, and metering work that other electricians must subcontract.

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Why DIY Is Dangerous and Illegal in NSW

Diagnosing an RCD trip safely requires:

A safe, controlled isolation procedure
An insulation-resistance tester (megohmmeter) operating at 250 V or 500 V
An earth-leakage clamp meter capable of measuring milliamp-level imbalance
A polarity tester and earth-loop impedance tester
An understanding of which device is fault-finding and which is the actual fault

DIY in this space is dangerous and illegal under NSW law. The *Gas and Electricity (Consumer Safety) Act 2017* makes any unlicensed fixed wiring work an offence, and the *Service and Installation Rules of NSW* reserve consumer-mains and switchboard work for licensed Level 2 ASP contractors. Beyond the law: working live in a domestic switchboard without testing tools or PPE has killed unlicensed renovators in Sydney. Insurance companies routinely deny fire claims where the cause is traced to unlicensed work, and conveyancing inspections will flag the work on sale.

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How to Safely Investigate This Fault

Stand on a dry surface and open the switchboard cover.
Stand on a dry surface and open the switchboard cover.
Locate the tripped RCD (toggle in mid or OFF position).
Locate the tripped RCD (toggle in mid or OFF position).
Turn OFF every individual breaker downstream of that RCD.
Turn OFF every individual breaker downstream of that RCD.
Reset the RCD to ON.
Reset the RCD to ON.
Re-energise circuits one breaker at a time, waiting 30 seconds between each.
Re-energise circuits one breaker at a time, waiting 30 seconds between each.
The breaker that re-trips the RCD identifies your faulty circuit.
The breaker that re-trips the RCD identifies your faulty circuit.
Unplug all appliances on that circuit. Reset and reintroduce one at a time.
Unplug all appliances on that circuit. Reset and reintroduce one at a time.
Press the RCD TEST button. If it doesn't trip, replace the RCD before furthe
Press the RCD TEST button. If it doesn't trip, replace the RCD before further use.
If the RCD won't hold with everything unplugged, leave it OFF and call **043
If the RCD won't hold with everything unplugged, leave it OFF and call 0433 462 902.

Frequently Asked Questions

What's the difference between an RCD and a safety switch?

None — they are the same device. "Safety switch" is the colloquial Australian name for what AS/NZS 3000 calls a Residual Current Device.

What is "nuisance tripping"?

Nuisance tripping is when an RCD trips without an obvious dangerous fault — usually because cumulative low-level leakage from several healthy appliances on one bank exceeds the 30 mA threshold. The fix is splitting circuits across more RCDs (RCBOs).

Should I test my RCD myself?

Yes — press the TEST button every three months. If the device does not trip, it has failed and must be replaced immediately. AS/NZS 3760 recommends three-monthly testing for residential installations.

My RCD trips when I switch on the dishwasher (or kettle, dryer, washing machine). Is the appliance dead?

Likely yes. The internal element insulation has degraded enough to leak to the metal body. Even if the appliance still "works," it is no longer safe to use until the element is replaced or the unit is retired.

Will replacing the RCD fix the problem?

Only if the RCD itself has failed. If the fault is in the wiring or an appliance, a new RCD will simply trip just like the old one. Diagnosis first, replacement second.

Why does my RCD trip when I plug something into a particular outlet?

The outlet itself may have damaged insulation, water ingress, or a damaged conductor inside the wall. We've found everything from screws driven into cables to rodent-damaged cores. Stop using the outlet and have it tested.

Do older Sydney homes need an RCD upgrade?

If your switchboard pre-dates 2000, the answer is almost certainly yes. Most pre-2000 boards have at most one RCD covering only a couple of circuits. Modern AS/NZS 3000 requires RCD protection on all final subcircuits — including lighting.

How long does an RCD last?

A well-installed RCD typically lasts 10–15 years. Coastal exposure (the Eastern Beaches, Northern Beaches, Sutherland Shire) can shorten that significantly due to salt-air corrosion of the contacts.

Is it safe to keep resetting my RCD if it keeps tripping back?

No — each reset into an active fault re-exposes you to the exact danger the RCD is designed to stop. If it trips a second time, stop resetting and treat that circuit as unsafe until a licensed electrician finds and fixes the underlying cause.

Should I worry if my RCD trips once but doesn't trip again?

Yes — a single trip still means a real earth leakage event occurred, and the fault is likely intermittent rather than gone. Moisture that dries out or an appliance that only leaks under certain load conditions can disappear and return, so have a licensed electrician run a diagnostic before the next trip catches you off guard.

Will my house catch fire if my RCD keeps tripping?

A tripping RCD is actually doing its job — but the underlying fault causing it can worsen over time, and degraded wiring insulation can eventually reach the point where arcing or overheating becomes a genuine fire risk. Treat repeated trips as an urgent warning, not a nuisance to reset away.

How much does it cost to diagnose an RCD fault in Sydney?

Cost varies depending on how many circuits need to be tested and the complexity of the fault — call 0433 462 902 for a fixed-price diagnostic quote before any work begins. Sydney Electrical Service provides upfront pricing with no hidden callout surprises across Sydney.

What's the difference between an RCD tripping and a circuit breaker tripping?

An RCD trips in response to earth leakage — current escaping outside its normal path, which is a direct shock and electrocution risk. A circuit breaker trips on overload or short circuit — too much current in the circuit — so the two devices protect against different dangers, and diagnosing one fault is not the same as diagnosing the other.