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ELECTRICAL FAULT GUIDE

RCD Trips When an Appliance Is Used

If the RCD trips when one appliance starts, heats, pumps or spins, the appliance, its plug, lead, socket or connected circuit is likely faulty.

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Stop if there is heat, burning, arcing, exposed parts or water near electrics

Do not remove consumer-unit covers, open sockets or test exposed conductors. Leave affected circuits off and call a registered electrician where danger signs or fixed wiring faults are present.

MOST LIKELY CAUSES

Start with these

Heating element leakage Common in washing machines, dishwashers, ovens and immersion heaters.
Motor or pump fault Insulation can fail when the motor starts or warms.
Damaged plug or cable Crushed, cut or overheated flex can leak to earth.
Socket or circuit issue A damaged outlet or fixed circuit may trip only under load.
◫ Symptom variations Match the exact behaviour before testing. ⌄
  • Trips immediately when the appliance is switched on
  • Trips only when the appliance begins heating
  • Trips during spin, pump or compressor start
  • Trips only at one socket
  • Trips after the appliance has been running for several minutes
✓ Quick checks Safe checks using plugs and front-panel switches only. ⌄
  1. Identify which device has operated.
  2. Note what was running when the fault happened.
  3. Unplug portable appliances on the affected circuit or RCD group.
  4. Check recent rain, leaks, cleaning, building work or newly connected equipment.
  5. Attempt one controlled reset only.
If it stays on: reconnect loads one at a time.
If it trips again: leave the affected item or circuit off and arrange testing.
1 Fix 1 — Stop using the appliance Follow this check without opening electrical accessories. ⌄

Process

Unplug it and do not try another socket as a workaround.

Success looks like: The rest of the installation remains stable with the appliance disconnected.
Failure means: If trips continue, another fault may also be present.
2 Fix 2 — Inspect plug and lead Follow this check without opening electrical accessories. ⌄

Process

Look for cuts, crushing, heat, loose pins or discolouration without opening the appliance.

Success looks like: Visible damage identifies an immediate repair or replacement need.
Failure means: No visible damage does not rule out an internal fault.
3 Fix 3 — Compare another low-power load Follow this check without opening electrical accessories. ⌄

Process

Use a known-good lamp or small appliance in the same socket if safe.

Success looks like: The known-good item works without tripping.
Failure means: If the socket trips with other loads, the outlet or circuit needs testing.
⌁ Common causes explained Why the fault may happen. ⌄

If the RCD trips when one appliance starts, heats, pumps or spins, the appliance, its plug, lead, socket or connected circuit is likely faulty.

Protective devices are usually reacting to a real electrical condition rather than causing it. Repeated resetting without finding the cause is not a repair.

⌘ Advanced diagnostics Technician-level testing for a competent electrician. ⌄
  • Portable appliance testing including protective conductor and insulation checks.
  • Leakage-current testing during heating or motor operation.
  • Insulation-resistance testing of the connected circuit.
  • Socket polarity, earth continuity and connection inspection.
  • Component testing of heaters, motors, pumps and filters.
◇ Tools needed Basic checks versus professional testing. ⌄

For basic checks

  • Torch
  • Phone or notepad
  • Known-good low-power appliance where appropriate

For a competent electrician

  • Approved voltage indicator and proving unit
  • Multifunction installation tester
  • Insulation-resistance tester
  • Leakage clamp meter
  • Suitable insulated tools and PPE
▣ Parts that may need replacing Common failed components linked to this fault. ⌄
  • Heating element
  • Motor
  • Pump
  • Mains filter
  • Power lead
  • Plug
  • Socket accessory
! When to call an electrician Conditions that should end DIY troubleshooting. ⌄
  • The fault remains with portable appliances unplugged.
  • There is burning, heat, buzzing, crackling or visible damage.
  • Water may have reached fixed electrical equipment.
  • The consumer unit is damaged, poorly labelled or has exposed parts.
  • The issue affects a shower, cooker, immersion heater, boiler or outdoor circuit.
  • The protective device will not reset or operates repeatedly.
? Frequently asked questions Common questions about this fault. ⌄

Should I keep resetting it?

No. One controlled reset can help establish whether the fault remains. Repeated resets without diagnosis are unsafe.

Does the protective device itself need replacing?

Not necessarily. The circuit and connected equipment should be tested before the device is replaced.

Can one appliance affect several rooms?

Yes. One protective device may control several circuits or areas.