Whole circuit / board nuisance tripping
A whole circuit or board protective device trips intermittently with no obvious single cause — affecting several loads — and you need a systematic way to corner it.
Safety first
Repeated tripping protects against a real fault. Don't bypass or upsize protection. Isolate before working and be ready for loss of supply to multiple loads.
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.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
One intermittent faulty load among several
Most likelyA single appliance/circuit with an intermittent fault trips the shared device only sometimes.
- 2
Cumulative loading/leakage near the limit
#2Combined load or leakage sits near the device threshold and trips on peaks.
- 3
Event-triggered (a specific load switching)
#3The trip happens when a particular load switches (inrush/leakage spike).
- 4
Loose connection / shared neutral
Least likelyA loose connection or shared-neutral issue causes intermittent faults.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModeLog each trip with what was running/switching at the time to find a correlation.
A correlation between trips and a load/event.
Correlated to a load/event — target that.
No correlation — split the board/circuit to divide and conquer.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Board nuisance tripping
→ step 2 - 2decision
Does logging correlate trips to a load/event?
Yes→ step 3No→ step 4 - 3result
Target the correlated load/event.
- 4decision
Does dividing the load localise the fault to a group?
Yes→ step 5No→ step 6 - 5result
Subdivide further to the culprit, then test that load.
- 6result
Trips with all split off — examine shared wiring/neutral/device.
Common mistakes apprentices make
- Upsizing or bypassing the protection instead of finding the fault.
- Not logging what's running when it trips.
- Testing everything at once instead of dividing the load.
- Forgetting shared-neutral and loose-connection causes.
When to stop & escalate
If the device itself is at fault or the loading is genuinely at the limit by design, that's a review rather than a quick fix. Never defeat the protection to stop nuisance trips.
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.
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Related faults
MCB (circuit breaker) keeps tripping
A circuit breaker trips repeatedly — instantly on reset, or after a load runs for a while — and you need to tell a short from an overload from a faulty breaker.
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.
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.
Learn the theory
How the gear and circuits behind this fault actually work.