Why can it trip with everything unplugged?
An RCD detects an imbalance in current and disconnects the supply as a protective action. Portable appliances are only part of what may be connected. Heating controls, an immersion heater, outdoor equipment or other fixed connections can remain on the installation. Wiring or accessories can also be affected by deterioration, damage or moisture.
Those are possibilities, not a diagnosis of your property. A trip after unplugging appliances does not prove that the RCD is defective or that the house needs rewiring. Do not remove covers or disconnect fixed equipment yourself.
Fixed wiring or connected equipment?
Tell the electrician whether the trip is immediate or intermittent, what loses power, and whether it coincides with rain, heating or particular equipment running. Include only observations you can make safely. The investigation separates connected-equipment problems from wiring faults using inspection and appropriate testing, rather than repeated resets.
Electrical Safety First explains that repeated RCD trips may involve an appliance or the wiring and should be investigated by an electrician. Read its RCD safety guidance.
What does the engineer investigate?
After agreeing the scope, the electrician considers the affected circuits, connected equipment, protective devices and the fault history. Safe isolation and testing are professional tasks. The findings determine whether equipment needs attention, a circuit needs repair, or further access is required. A protective device is not bypassed to keep the supply on.
If it is an individual breaker rather than an RCD, see circuit breaker trips. For board-related symptoms, see consumer-unit fault assessment.
Why might a second visit be needed?
An intermittent fault may not occur during the first visit. Concealed cables, restricted access, drying after water damage or a particular replacement part may also mean more work is needed. Ask what has been checked, what must remain unused and what a return visit would cover. Any further work is quoted before starting.
Our call-out is £50 plus VAT (£60 total). Read how fault finding is arranged or send your RCD symptoms. Do not wait for an online reply if there is immediate danger.
Your questions answered
Does unplugging everything prove the fixed wiring is faulty?
No. Fixed equipment may still be connected, and several possible faults can produce similar symptoms. An electrician needs to investigate before distinguishing wiring, equipment and protective-device problems.
What if the RCD will not reset?
Do not force or bypass it, and do not keep attempting resets. Avoid using the affected installation until professional advice has established what is safe.