A Type AC RCD does not automatically make an EICR unsatisfactory. Current industry guidance says a Type AC device may attract a C3 recommendation where electronic equipment producing DC components is connected, or could foreseeably be connected. If the RCD is tested and does not operate correctly, however, a C2 classification may be appropriate. Type A is generally better suited to modern electronic loads, but it is not automatically suitable for every possible circuit either.
So which type can “fail” an EICR?
Either type could be associated with an unsatisfactory report if the protective device is defective or unsuitable in a way that creates potential danger. The important distinction is that the mere presence of a Type AC RCD is not, by itself, an automatic EICR failure.
Key Takeaways
- Type AC responds to sinusoidal AC residual current and has limitations where DC components may be present.
- Type A also responds to pulsating DC residual current, making it more appropriate for many circuits supplying modern electronic equipment.
- A Type AC RCD may receive a C3 where equipment producing DC components is connected or could foreseeably be connected.
- A C3 means improvement is recommended and, on its own, does not make the EICR unsatisfactory.
- If an RCD does not operate correctly when tested, a C2 may be appropriate regardless of whether the device is Type AC or Type A.
What Is the Difference Between Type AC and Type A RCDs?
Both devices are residual current devices, but they are designed to respond to different forms of residual current. A Type AC RCD is intended to respond to sinusoidal alternating residual current. A Type A RCD can also respond to pulsating direct residual current, which can be produced by electronic equipment.
That distinction matters because modern homes contain far more electronic power supplies, LED drivers, dimmers, induction equipment and other electronically controlled loads than older installations were originally designed around.
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Does a Type AC RCD Automatically Fail an EICR?
No. Finding a Type AC RCD does not automatically make an existing electrical installation unsatisfactory.
Current Electrical Safety First and Wiring Regulations Advisory Group guidance specifically addresses this situation. Where it is known that the connected loads cannot produce DC components capable of impairing the RCD, no recommendation code may be necessary.
The inspector therefore has to consider the circuit the device protects, the equipment connected to it, what could reasonably be connected in normal use, manufacturer requirements and the test results. The decision cannot be made simply from the letters printed on the front of the RCD.
An EICR assesses an existing installation for continued use.
It is not simply a checklist asking whether every component matches the preferred specification for a completely new installation.
When Can a Type AC RCD Receive a C3?
A C3 may be appropriate where equipment that can produce DC components is connected to a circuit protected by a Type AC RCD, or where such equipment could foreseeably be connected.
The reason is that residual DC components from electronic equipment can affect a Type AC device and, in some circumstances, desensitise or “blind” it. The RCD may then not respond as intended to a fault.
A C3 means improvement recommended. For rented properties in England, current GOV.UK guidance expressly states that a C3 does not, by itself, require remedial work for the report to be considered satisfactory.
If you want a deeper explanation of report classifications rather than RCD types, the separate guide to
C1, C2, C3 and FI codes on an EICR
covers that subject in more detail.
When Can an RCD Result in a C2?
If inspection and testing confirms that an RCD does not operate correctly, current industry guidance says a C2 classification may be appropriate. C2 means the condition is potentially dangerous.
This is an important distinction. The C2 is not being issued merely because the device is labelled Type AC. It is being issued because testing has established a problem with the protective function of the RCD.
The same principle applies to a Type A device. A Type A RCD is not given an automatic pass simply because it is the newer or more capable type. If it is defective, incorrectly selected or fails the relevant testing, the inspector has to assess the actual safety consequence.
Can a Type A RCD Still Be Unsuitable?
Yes. Type A is suitable for many modern circuits, but it is not a universal solution for every electrical load.
Some equipment can produce residual-current characteristics that require a different type of device, such as Type F or Type B, or another specific protective arrangement. The correct choice depends on the connected equipment, the expected residual current and the manufacturer's instructions.
This is particularly important when specialised electronic equipment, power conversion equipment or certain charging systems are involved. The inspector should assess the actual circuit rather than working on the assumption that “Type A always passes”.
Why Do Modern Electronics Matter to RCD Selection?
Traditional resistive loads produce a relatively straightforward AC waveform. Modern electronic equipment can behave differently because rectifiers, power supplies, inverters and electronic controls can introduce pulsating or smooth DC components into residual fault current.
Type AC devices are more vulnerable to this problem. Official IET guidance explains that DC components can saturate the magnetic core of a Type AC RCD, potentially preventing it from operating as intended.
This is why a Type AC device protecting a circuit where modern electronic equipment can reasonably be expected deserves closer consideration than a Type AC device serving a known fixed load with no DC component.
Type AC Is Different from Having No RCD Protection
An existing Type AC device and complete absence of required RCD protection are not the same EICR observation.
If your question is whether a circuit with no RCD protection can make an EICR unsatisfactory, that has different coding considerations. The dedicated guide on
missing RCD protection on an EICR
covers that separate issue.
Which Version of BS 7671 Applies in August 2026?
BS 7671:2018+A4:2026 was published on 15 April 2026. The IET confirms that the previous BS 7671:2018+A2:2022+A3:2024 edition remains valid during a six-month transition period until 15 October 2026, and installers may work to either edition during that period.
That transition should not be interpreted as an instruction to automatically fail every existing Type AC RCD. Periodic inspection remains an assessment of the condition and suitability of the existing installation, including the device, the loads it serves and the results of testing.
The current IET guidance continues to emphasise that the appropriate RCD type must be selected with regard to the residual current characteristics produced by the equipment being protected.
What Should You Do If Your EICR Identifies a Type AC RCD?
Start with the actual observation and classification on the report rather than assuming the consumer unit has failed simply because Type AC protection is present.
A useful assessment should establish:
- which circuit the Type AC RCD protects;
- what equipment is currently connected;
- what equipment could reasonably be connected during normal use;
- whether the equipment manufacturer specifies a particular RCD type;
- whether the RCD operated correctly during testing; and
- whether the observation is C3, C2 or does not require a classification code.
If the report recommends changes to the protective devices or board, the next step may be to
have the consumer unit checked
before deciding whether individual RCDs, RCBOs or the wider board arrangement should be altered.
Replacement should be based on the installation and the protection actually required, not simply on the assumption that every Type AC device must be removed from every existing property.
References & Standards
The technical and EICR classification points in this article were checked against current official and industry guidance available on 21 August 2026.
Need the RCD Protection on Your EICR Checked?
If an EICR has raised a question about Type AC, Type A or the protection at your consumer unit, the important step is to assess the circuit, connected equipment and test results before deciding what work is actually required.
Arrange an EICR