An RCD that trips once after a real fault may be doing exactly what it should. An RCD that will not reset, fails its test button, or trips repeatedly without a clear cause needs attention. RCD replacement timing is not simply a matter of counting years since installation. The condition of the device, its test results, the type of electrical installation, and changes in how the property uses power all matter.
For homeowners, landlords, and site managers, the practical rule is simple: do not replace a working RCD just because it is old, but do not wait for a complete failure if testing or professional inspection identifies a problem.
What an RCD does
A residual current device, usually called an RCD, is a safety device designed to disconnect power quickly when it detects electricity flowing where it should not. This can happen through damaged cable insulation, a faulty appliance, moisture ingress, or contact with live parts.
It is not the same as a circuit breaker. A circuit breaker protects cables from overload and short circuits. An RCD provides additional protection against electric shock and certain fire risks caused by earth leakage. Modern consumer units often use RCBOs instead, which provide circuit breaker and residual-current protection for individual circuits.
Because an RCD is a life-safety device, it should be tested and maintained rather than treated as fit-and-forget equipment.
RCD replacement timing: there is no fixed age limit
There is no universal rule that says every RCD must be replaced after a set number of years. A good-quality device may remain serviceable for many years if it operates correctly and the installation is in good condition. Equally, an RCD in a damp outbuilding, busy rental property, workshop, or caravan park distribution board may face harder conditions and need earlier replacement.
The right time to replace it is normally determined by testing and condition, not age alone. An electrician can check whether the RCD trips at the required level and within the required time, whether its terminals are sound, and whether the device remains suitable for the circuits and equipment it protects.
A periodic electrical inspection, known in the UK as an EICR, is often when these issues come to light. For landlords, regular inspection is particularly important because electrical safety duties apply even when tenants have not reported a fault.
Signs an RCD should be checked or replaced
A tripped RCD is not automatically a failed RCD. It may have correctly detected a fault on a circuit or appliance. However, several warning signs call for prompt investigation by a qualified electrician.
If the test button does not trip the RCD, the device cannot be relied upon until it has been checked. If it trips but will not reset after circuits and appliances have been disconnected, there may be a fault in the wiring, the consumer unit, or the RCD itself.
Repeated tripping also needs proper fault finding. Common causes include an appliance with damaged heating elements, outdoor equipment affected by water, a deteriorating cable, or too much combined leakage from multiple electronic devices. Replacing the RCD without identifying the cause may not solve the problem.
Physical condition matters too. Signs such as heat damage, discoloration, loose terminals, cracking, corrosion, a burning smell, or buzzing from the consumer unit should be treated as urgent. Switch off power if it is safe to do so and arrange professional help. Do not keep resetting a device that is tripping repeatedly, and never bypass an RCD to keep a circuit running.
Test the button, but understand its limits
Most RCDs have a button marked “T” or “Test.” Pressing it simulates an imbalance and should switch the device off. It is a useful basic check, and the manufacturer’s instructions should state how often it should be tested. Many installations recommend a routine user test, commonly every six months, although some older equipment may specify a different interval.
The test button only confirms that the internal mechanism responds to that particular test. It does not prove the RCD is tripping at the correct speed under all conditions, nor does it identify poor connections, insulation damage, or unsuitable circuit design.
After pressing the button, reset the RCD and check that essential circuits have returned to service. If it will not reset, leave it off and have the installation checked. Where power loss could affect freezers, alarms, care equipment, servers, or site operations, plan the test for a suitable time.
When an upgrade makes more sense than a like-for-like replacement
Sometimes a failed RCD can be replaced with an equivalent device. In other cases, the better option is an upgrade to the consumer unit or distribution board arrangement.
Older installations may have one RCD protecting most or all circuits. If it trips, the property can lose lights, sockets, heating controls, refrigeration, and alarm equipment at the same time. Splitting circuits across separate RCDs or fitting individual RCBO protection can reduce disruption and make faults easier to locate.
The type of RCD also matters. Older Type AC devices may not be appropriate for every modern load. Equipment such as induction cooktops, washing machines, heat pumps, solar systems, battery storage, variable-speed drives, and EV charging equipment can require a different type of residual-current protection. The correct choice depends on the equipment, the circuit design, and the manufacturer requirements.
For a home, this may be a sensible improvement during a rewire, kitchen renovation, EV charger installation, or consumer unit replacement. For commercial, industrial, and caravan park sites, the decision may also depend on avoiding unnecessary downtime and keeping essential services separated.
Planned inspections prevent avoidable outages
Waiting until an RCD fails is rarely the best maintenance plan. A planned inspection can identify weak points before they become a shutdown, especially in properties with heavy use, outdoor circuits, communal areas, or frequent tenant turnover.
Landlords should keep electrical inspection records and act on any observations that affect safety. Estate agents and property managers can reduce last-minute callouts by checking consumer units as part of changeover maintenance. Commercial operators should consider how a trip would affect lighting, IT, refrigeration, security, production equipment, or customer access.
Caravan parks need particular care because outdoor hook-up points, distribution equipment, weather exposure, and seasonal occupancy all place demands on electrical protection. Testing should be scheduled around the operating pattern of the site, not left until peak season.
What an electrician will check
A qualified electrician will not decide on replacement from the front of the consumer unit alone. They will inspect the device and enclosure, test RCD trip times and trip currents with suitable equipment, check circuit insulation resistance where appropriate, and investigate earth leakage or faults causing trips.
They can also assess whether the current protection arrangement meets the needs of the installation. This is useful when a property has been extended, converted, rewired in stages, or fitted with higher-demand equipment since the consumer unit was installed.
If replacement is needed, the work should be selected and installed to suit the existing system and verified with the correct testing. In England, consumer unit work is generally notifiable under Part P building regulations, so using a properly qualified contractor helps ensure the job is documented correctly.
A practical decision for property owners
Do not make RCD replacement timing a guess based on the age of the consumer unit. Test the device using its built-in button as instructed, arrange professional testing through periodic inspection, and act quickly on failures, repeated trips, heat damage, or signs of corrosion.
If you are planning electrical alterations or experiencing unexplained tripping in Lancaster, Morecambe, Heysham, Carnforth, Caton, or Forton, NS Electrical can assess the fault, test the protection in place, and advise whether repair, replacement, or an upgrade is the sensible next step. A properly working RCD is quiet protection – you only notice it when it has done its job.