AdvancedMedium risk

RCD trips randomly with no obvious pattern

An RCD trips occasionally with nothing obviously changing — not tied to a clear appliance, weather, or time — the frustrating 'tripped again overnight' type.

Start fault-finding

Safety first

Intermittent earth-leakage is still a shock-risk indicator — don't disable the RCD. Treat any leakage source you find as a real fault.

Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.

Full detail — causes, the why, and common mistakes.

Likely causes

Ranked from most to least likely.

1
An intermittently-faulty appliance
Most likely
A device that only leaks at certain points in its cycle (heating element, motor) trips the RCD unpredictably.
2
Cumulative leakage tipped by a transient
#2
Standing leakage near the threshold trips when something switches on (inrush spike).
3
Moisture/condensation appearing intermittently
#3
Condensation overnight or after weather creates an occasional leakage path.
4
Intermittent wiring fault
Least likely
A marginal cable or connection leaks only when disturbed/flexed.

Reports are saved on this device to reflect what you actually find.

Premium fault tree

The full ranked causes, test sequence and flowchart for this fault are part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Testing sequence

Work through one test at a time. Expected reading and what each result means.

Test 1 of 3

Log each trip with time, weather, and what was running/cycling to find any hidden pattern.

Expected reading

A correlation emerges (a cycling appliance, time, weather).

Your actual reading

If it passes

Correlated — target that appliance/condition.

If it fails

No pattern yet — measure standing leakage and split the load.

Often leads toRCD / RCBO keeps tripping RCD nuisance tripping with lots of electronics

View all expected readings at once

1. Log each trip with time, weather, and what was running/cycling to find any hidden pattern.

A correlation emerges (a cycling appliance, time, weather).

2. Measure total standing earth-leakage and split the load to see how close it sits to the threshold.

Standing leakage comfortably below the RCD threshold.

3. Insulation-test suspect circuits (ideally during/after conditions when it trips) and check for moisture/marginal connections.

Good insulation; no moisture or marginal joints.

Full test sequence

The step-by-step test flow with expected readings for this fault is part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Fault-finding flowchart

The same logic as a decision tree.

1
start
RCD trips randomly
→ step 2
2
decision
Does logging reveal a correlation (appliance/time/weather)?
Yes→ step 3No→ step 4
3
result
Target the correlated appliance/condition.
4
decision
Is standing leakage comfortably below threshold?
Yes→ step 5No→ step 6
5
decision
Do insulation tests / inspection find an intermittent source?
Yes→ step 7No→ step 8
6
result
Near threshold — a transient tips it; redistribute circuits.
7
result
Intermittent leakage source found — repair it.
8
result
Keep logging to catch the rare event.

Common mistakes apprentices make

Disabling/swapping the RCD instead of finding the source.
Not logging conditions to reveal a pattern.
Ignoring overnight condensation as a cause.
Testing only when dry/idle and finding nothing.

When to stop & escalate

Genuinely elusive intermittent leakage may need monitoring over time or specialist help. Cumulative-leakage problems may need circuits redistributed — never remove the protection.

If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.

Related faults

RCD / RCBO faults

RCD / RCBO keeps tripping

An RCD or RCBO trips repeatedly — immediately on reset, randomly during the day, or only when certain equipment runs. The earth-leakage protection is doing its job; something is leaking.

5 causes4 test steps

QualifiedHigh risk

RCD / RCBO faults Premium

RCD nuisance tripping with lots of electronics

An RCD trips intermittently with no single faulty appliance — typically where many electronic devices (with filters/SMPS) share one RCD, each adding a little standing leakage.

4 causes3 test steps

AdvancedMedium risk

General testing Premium

Intermittent fault that's hard to reproduce

Something fails occasionally — random trips, dropouts, or stoppages — but works fine when you go to look at it. The classic 'can't fault it on the bench' problem.

5 causes3 test steps

AdvancedMedium risk