Morgan Allen: Created page with "= RCD Fault Finding Checklist = == Purpose == To provide a structured, practical method for identifying why an RCD is tripping and locating the fault safely and efficiently. == Common Reasons An RCD Trips == * Earth leakage on a circuit (most common cause) * Faulty appliance plugged into a socket circuit * Damaged cable (nails, screws, heat, crushing) * Moisture ingress into accessories or outdoor equipment * Neutral-to-earth fault anywhere on the protected side * Inc..."

2026-06-10T13:56:16Z

Created page with "= RCD Fault Finding Checklist = == Purpose == To provide a structured, practical method for identifying why an RCD is tripping and locating the fault safely and efficiently. == Common Reasons An RCD Trips == * Earth leakage on a circuit (most common cause) * Faulty appliance plugged into a socket circuit * Damaged cable (nails, screws, heat, crushing) * Moisture ingress into accessories or outdoor equipment * Neutral-to-earth fault anywhere on the protected side * Inc..."

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= RCD Fault Finding Checklist =

== Purpose ==
To provide a structured, practical method for identifying why an RCD is tripping and locating the fault safely and efficiently.

== Common Reasons An RCD Trips ==

* Earth leakage on a circuit (most common cause)
* Faulty appliance plugged into a socket circuit
* Damaged cable (nails, screws, heat, crushing)
* Moisture ingress into accessories or outdoor equipment
* Neutral-to-earth fault anywhere on the protected side
* Incorrect neutral connection (borrowed neutral / mixed neutrals)
* Faulty RCD device
* Overcrowded or poorly maintained wiring causing leakage
* External equipment faults (garden lighting, outbuildings, showers, pumps)

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== Step-by-Step Fault Finding Procedure ==

=== 1. Confirm The Fault ===
* Check what exactly is tripping:
* RCD main switch
* Individual RCBO
* Note if it trips instantly or after a delay.
* Try to identify when it started (recent work, weather change, new appliance).

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=== 2. Initial Isolation ===
* Switch OFF all MCBs/RCBOs on the affected RCD.
* Reset the RCD.
* If it holds, the fault is downstream on a circuit.
* If it still trips with everything off, suspect:
* Faulty RCD
* Neutral issue in the board

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=== 3. Re-Energise One Circuit At A Time ===
* Turn circuits back on one by one.
* Wait after each circuit is energised.
* Identify which circuit causes the RCD to trip.

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=== 4. Isolate The Problem Circuit ===
* Leave the faulty circuit OFF.
* Confirm other circuits operate normally.
* Focus investigation only on the suspect circuit.

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=== 5. Break Down The Circuit (Section Testing) ===
* Disconnect all loads (sockets, appliances, accessories).
* Test RCD again with circuit energised but unloaded.
* If it now holds:
* Fault is in a device or appliance

If it still trips:
* Fault is in fixed wiring

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=== 6. Appliance Check (If Socket Circuit) ===
* Unplug everything on the circuit.
* Pay attention to:
* Washing machines
* Dishwashers
* Kettles
* Outdoor tools and garden equipment
* Plug appliances back in one at a time to identify the faulty item.

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=== 7. Fixed Wiring Checks ===
* Visually inspect:
* Sockets (especially outdoor or damp areas)
* Junction boxes
* External lighting
* Look for signs of:
* Water ingress
* Heat damage
* Crushed or pinched cables
* Check for neutral-to-earth contact faults.

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=== 8. Test For Cable Faults ===
* Carry out insulation resistance testing on suspect circuit.
* Test between:
* Live and earth
* Neutral and earth
* Live and neutral
* Look for low insulation resistance readings indicating leakage.

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=== 9. Check For Neutral Issues In Board ===
* Inspect neutral bar carefully.
* Look for:
* Loose neutrals
* Borrowed neutrals between circuits
* Incorrect neutral pairing on RCBOs
* Especially common after consumer unit changes.

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=== 10. RCD Condition Check ===
* If no fault is found in wiring or appliances:
* Test RCD using appropriate test equipment
* Check trip times and sensitivity
* Replace RCD if it fails tests or behaves inconsistently.

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== Common Real-World Causes ==
* Outdoor socket full of water
* Fridge/freezer developing earth leakage when compressor starts
* Boiler or immersion heater insulation breakdown
* Damaged garden lighting cable
* Washing machine heating element leaking to earth
* Shared neutral mistakes after alterations

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== JME Standard ==
All RCD faults must be traced systematically by elimination, ensuring circuits, appliances, and protective devices are checked in a controlled and safe manner before replacement or repair decisions are made.

RCD/RCBO Tripping - Revision history