RCD won't reset at all
The RCD won't stay reset — the toggle won't latch up, or it trips instantly every time, so the circuit can't be restored.
Safety first
Instant tripping means a strong leakage or a fault present. Don't force or strap it. Isolate the load and find the fault before relying on the circuit.
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
Hard earth-leakage / neutral-earth fault present
Most likelyA solid leakage path (including a neutral-earth fault) trips the RCD the instant it's reset.
- 2
Downstream fault on a connected circuit
#2A faulty appliance or circuit holds the leakage so it can't reset until removed.
- 3
Wiring fault at the RCD (e.g. swapped neutrals)
#3Mis-wired neutrals (borrowed/shared, or load neutral on the wrong side) trip an RCD immediately.
- 4
Faulty RCD
Least likelyA mechanically failed RCD won't latch even with no fault.
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.
Turn off / disconnect all downstream loads and circuits, then attempt the reset.
RCD resets and holds with everything downstream off.
It resets with load off — a downstream circuit/appliance has the fault.
Won't reset even with load off — suspect wiring at the RCD or a faulty RCD.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
RCD won't reset
→ step 2 - 2decision
Does it reset with all downstream load off?
Yes→ step 3No→ step 4 - 3decision
Reintroducing circuits, does one prevent the reset?
Yes→ step 5No→ step 6 - 4decision
Is the RCD wiring correct and does the RCD test within spec?
Yes→ step 7No→ step 8 - 5result
That circuit is faulty — isolate and insulation-test it.
- 6result
Re-examine wiring at the RCD.
- 7result
Re-check downstream circuits.
- 8result
Mis-wired neutrals or failed RCD — correct wiring or replace RCD.
Common mistakes apprentices make
- Forcing/strapping the RCD instead of finding the fault.
- Not isolating downstream load before testing the reset.
- Missing a borrowed/shared neutral that trips the RCD.
- Condemning the RCD before checking wiring and downstream faults.
When to stop & escalate
A hard earth or neutral-earth fault in fixed wiring needs a qualified repair and retest. Never restore the circuit by removing the RCD 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 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.
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.
RCD trips only in wet weather or after wash-down
The RCD holds fine when dry but trips after rain, washdown, or in damp conditions — pointing to moisture creating an earth-leakage path somewhere outdoors or in wet areas.
Learn the theory
How the gear and circuits behind this fault actually work.