Leakage Current: What It Is and Why Your RCD Sometimes Trips
Your RCD trips, but an electrician can't find a fault? The cause might not be a fault at all — it could be leakage current adding up across several devices on one circuit. This page helps you understand what's going on, not measure a live circuit yourself.
How to make sense of what's happening
Understand what leakage current actually is
Almost every electronic device has a small current flowing to earth (PE) — through normal insulation resistance, built-in EMC/RFI filters, or capacitive coupling in long cables. That's not automatically a fault; it's a normal, expected part of how the equipment works.
Tell standing leakage apart from fault leakage
Standing (background) leakage is present all the time, even when everything's working correctly. Fault leakage comes from damaged insulation, moisture ingress or a degraded component. A trend over time tells you more than a single reading.
See why an RCD can trip with nothing broken
Leakage current from several devices on one circuit adds together. Once that total gets close to the RCD's/RCBO's own rated residual current, it can trip — even if not one device is actually faulty. That's nuisance tripping.
Know when it's time to call an electrician
Repeated or unpredictable tripping, a reading that climbs over time, or any suspicion of moisture or damaged insulation — that's a job for a certified electrician, not DIY.
What's worth knowing about leakage current
Typical rated residual current for a general-purpose household RCD
The general principle: total leakage on a circuit should stay well below the RCD's own rated residual current. The exact acceptance thresholds for your installation always depend on the applicable standard and the specific RCD's datasheet — that's for an electrician to check, not to guess at.
It's a normal part of how devices work
EMC/RFI filters in chargers, LED drivers and IT equipment, plus ordinary insulation resistance, all produce a small, expected leakage current — on its own, that's not a red flag.
Standing leakage vs fault leakage
Standing leakage is steady and scales with what's connected. Fault leakage tends to rise over time or spike when a specific device switches on — trend, not a single number, tells the real story.
Why more devices means more nuisance tripping
Each device contributes a little, but on one circuit those contributions add up. That's the most common explanation for an office, server rack or workshop full of power supplies where the RCD "trips for no reason".
The usual sources of leakage
EMC filters in IT gear and chargers, variable frequency drives (VFDs) with shielded output cables, long cable runs, heaters, and anywhere moisture has gotten into damaged insulation.
How to reduce nuisance tripping
Split the load across several RCDs/RCBOs instead of putting everything behind one. Fix damaged insulation once it's been identified, rather than working around it. Watch for too many filtered devices piling up on one circuit.
What this page gives you
An explanation to help you understand the situation — before or instead of calling an electrician
- {'t': 'A plain-language explanation', 'd': "What leakage current is, and why it's present in almost every device you own."}
- {'t': 'How to tell standing from fault leakage', 'd': "How to think about a reading — what's normal, what's worth watching."}
- {'t': 'A list of the usual sources', 'd': 'EMC filters, VFDs, long cables, moisture — what typically adds up on a circuit.'}
- {'t': 'Practical steps you can take', 'd': 'Splitting the load and avoiding filter stacking — without measuring anything live.'}
- {'t': 'A clear line to an electrician', 'd': "When it stops being a DIY question — and why measurement and panel work stay a professional's job."}
Frequently asked questions
Does leakage current mean something is broken?
Not necessarily. A small leakage current is normal in nearly every electrical device, coming from filters and insulation. A rising trend over time is the real warning sign, not the mere presence of leakage.
Why does my RCD trip when nothing seems faulty?
Most likely, leakage from several devices on the same circuit is adding up and getting close to the RCD's own rated residual current. That's nuisance tripping — the fix is usually splitting the load, not hunting for one "guilty" device.
Can I measure leakage current myself at home?
It's measured with a dedicated leakage clamp meter that reads line and neutral together, plus RCD test instruments for ramp testing. That's work on a live circuit, which makes it a certified electrician's job, not a DIY one.
What usually increases leakage current in a home?
EMC filters in IT equipment and chargers, VFDs, long cable runs, heaters, and moisture getting into damaged insulation or outdoor sockets.
What should I do if my RCD keeps tripping?
Try splitting the load across several RCDs/RCBOs and avoid stacking too many filtered devices on one circuit. If it keeps happening or a reading is rising, call a certified electrician — actual measurement and testing is their job.
Not sure why your RCD keeps tripping?
Tell us what's happening — we'll help you work out whether it's normal or worth an electrician's inspection.