Helpful video reference. We use John Ward's (jwflame) "Washing Machine Keeps Tripping the RCD... But It Wasn't the Machine!" as the video reference here. John Ward is a qualified UK electrician based in Poole, Dorset, who runs the Flameport electrical YouTube channel. In this video he investigates a customer call-out where the washing machine appeared to be tripping the RCD on every cycle - and finds the real fault elsewhere. It is worth watching before you blame the appliance.
1. Note exactly when the RCD trips
The timing tells you a lot about where the fault is.
- Immediately on plugging in: the appliance has a hard fault - a direct connection between live and earth inside it. This is a genuine appliance fault.
- When the motor starts or the programme changes: the fault is in the motor winding or inverter drive. Washing machines often trip when the motor kicks in for the spin cycle. Could be the appliance, or could be cumulative leakage being pushed over the RCD threshold at that moment (see Step 6).
- Randomly or after a long run: heat-related fault. Insulation that passes a cold test may fail when warm.
- When nothing is running: the fault is not in a plug-in appliance at all. Either a wiring fault or an appliance left plugged in even when apparently switched off (some appliances draw standby current to earth).
2. Find which RCD covers which circuits
Open your consumer unit door and look at the label. In a modern all-RCBO board every circuit has its own device, so the tripping device tells you exactly which circuit is involved. In a split-load board, a single RCD may cover half the circuits in the house - the kitchen ring, the utility ring and parts of the lighting, for example.
Write down every circuit on that RCD. You need to think about every socket, light and fixed appliance on those circuits when looking for the fault.
3. Unplug everything on those circuits
Before unplugging, note what is where so you can restore things in a controlled order. Then unplug every appliance connected to the suspect RCD's circuits: washing machine, dishwasher, fridge, freezer, toaster, kettle, everything. Switch off lamps at the wall rather than leaving them plugged in.
Now reset the RCD. If it trips immediately with nothing plugged in, go directly to Step 7 - the fault is in the fixed wiring, not an appliance.
4. Plug appliances back in one at a time
With the RCD holding, reconnect appliances one at a time and give each one time to run. If an appliance trips the RCD the moment it is plugged in, that one is immediately suspect. If it trips only when a particular appliance starts a programme, make a note and move to Step 5.
Work through every appliance on the circuit. It is possible that two appliances together cause the problem, neither one alone being enough to trip the RCD. This is cumulative leakage - see Step 6.
5. Test the suspect appliance on a different circuit
Move the suspect appliance to a socket on a different circuit, protected by a different RCD. Run it through its full programme. If the RCD on the second circuit also trips, the appliance itself has a genuine fault - it needs a repair or replacement.
If the appliance runs without fault on the second circuit, the problem is more subtle. The appliance may be generating just enough earth leakage to push the total leakage current on its usual circuit over the 30 mA trip threshold - especially when combined with other appliances. That brings us to cumulative leakage.
Alternatively, try the appliance with a plug-in RCD adapter. If the adapter trips when nothing else is on the circuit, the appliance has a leakage problem of its own.
6. Understand cumulative leakage
Every appliance with a motor, inverter or switched-mode power supply generates a small amount of earth leakage current. Individually, each one is well within the 30 mA trip threshold of a 30 mA RCD. Together on the same RCD they add up.
A washing machine with a brushless motor, a dishwasher with an inverter heater element and a fridge compressor can contribute 8-10 mA each in normal operation. Add a couple of other small appliances and the combined leakage is close to 30 mA even before anything has actually failed. Then when the washing machine's motor starts the spin cycle and draws a surge, the combined leakage momentarily exceeds 30 mA and the RCD trips.
This was the scenario in John Ward's video: the washing machine was not faulty. The accumulated leakage from several appliances, all healthy in isolation, exceeded the threshold when the spin programme started.
The solution is usually to move some appliances to a different RCD's circuits. In an all-RCBO board each circuit is already independent, so this problem rarely arises. In a split-load board with a shared RCD, an electrician can rearrange which circuits fall under which protection device.
7. If the RCD trips with nothing plugged in
This means the fault is in the fixed wiring itself - cables buried in walls, the wiring to fixed appliances like the cooker or immersion heater, or the wiring to outside circuits. This is not something a homeowner should attempt to trace without professional equipment. An electrician will use a multifunction tester to run an insulation resistance test on each circuit, which identifies where the fault is.
Common causes of wiring faults that trip an RCD with no plug-in appliances connected: damaged cable in a wall (from a drill or nail), water ingress into an outdoor or garage circuit, or deteriorated insulation in old rubber-sheathed wiring.
When to call us
If you have worked through the steps above and still cannot find the fault, or if the RCD trips with nothing connected, Richard can carry out an insulation resistance test on each circuit to find exactly where the problem is. Fault-finding call-outs in Sandwich and east Kent are charged at the standard hourly rate with no call-out fee during business hours.
RCD fault in Sandwich?
Richard can trace wiring faults and appliance leakage with professional test equipment. Most call-outs are resolved in a single visit.
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