. AFDD RCBO combines an arc fault detection device with a residual current circuit breaker with overcurrent protection. In a declared combined unit, arc-fault detection, residual-current protection, overload protection and short-circuit protection serve the same final circuit. Each function responds to a different fault condition.
To choose the right device, match all of those functions to the circuit: supply voltage and frequency, rated current, overcurrent curve, residual-current type and sensitivity, short-circuit capacity, neutral arrangement and distribution-board compatibility. “AFDD + RCBO” describes the protection combination; it is not a complete specification.
Klíčové poznatky
- A hazardous series arc can occur without enough overcurrent or residual current to operate an ordinary RCBO.
- B or C describes the overcurrent characteristic; Type A describes residual-current detection. These labels answer different questions.
- The device’s ampere rating, milliampere sensitivity and kiloampere breaking capacity are separate limits.
- A combined device must fit the circuit and the declared board assembly. Physical DIN-rail fit alone is insufficient.
For orientation across standards, testing and related devices, see what an AFDD does and how it works.
How the Combined Protection Works
The protection functions operate alongside one another. The device does not wait for an arc fault, earth leakage and overload to occur together. A qualifying fault detected by any included protection function can cause the circuit to open.
Arc-detection electronics evaluate electrical signatures associated with hazardous arcing. The residual-current function detects an imbalance between outgoing and returning current in the monitored conductors. The overcurrent function responds according to its time-current characteristic: sustained overload and high short-circuit current require different responses.
The following is a functional explanation, not an internal construction or terminal diagram. The sensors, electronics, trip mechanism and contact arrangement depend on the exact product design. IEC 62606 recognizes different AFDD construction arrangements, including integration with other protective devices. IEC 62606 scope
| Poruchový stav | Relevant function in a combined AFDD RCBO | What determines operation |
|---|---|---|
| Hazardous series or parallel arcing | Detekce obloukového zkratu | The device’s detection criteria and declared operating conditions |
| Current returning outside the monitored circuit conductors | Ochrana proti reziduálnímu proudu | Residual waveform, magnitude and operating characteristic |
| Sustained current above the circuit’s permitted loading | Ochrana proti přetížení | Rated current and the time-current characteristic, considering installation conditions |
| High current from a short circuit | Ochrana proti zkratu | Fault current, trip characteristic and interrupting capacity |
Why the RCBO Function Alone May Miss an Arc
Consider a deteriorating connection in series with a load. Its resistance can limit the circuit current while the connection arcs. The outgoing and returning currents may still balance. In that case, neither a large overcurrent nor a sufficient residual-current imbalance is guaranteed.
This explains why adding arc detection can address a gap in conventional protection. It does not mean an AFDD detects every hot connection or prevents every electrical fire. Sound connections, suitable conductors and installation verification remain necessary. The Schneider Electrical Installation Guide on AFDD protection explains its relationship to conventional final-circuit protection.
Parallel faults can involve line and neutral or line and earth. Depending on the fault, an overcurrent or residual-current function may also respond. Do not assume that every trip of a combined device proves an arc fault; use the model’s diagnostic indication and instructions.
What “AFDD + RCBO” Means When Ordering
For an integrated product, the phrase means the manufacturer provides the arc-detection and RCBO functions together in one declared device. A separate arc-detection unit assembled with a protective device is a different construction route and must use the manufacturer-declared combination.
The plus sign does not authorize combining arbitrary AFDD and RCBO products. It also does not establish neutral switching, module width, surge protection or certification for a particular market.
If the purchasing question is whether an ordinary RCBO and an AFDD provide the same functions, use the separate RCBO versus AFDD comparison. For the integrated product, the useful next step is to turn the circuit requirements into ratings.
Choose the Device from the Circuit Requirements
Begin with the circuit design and expected load behavior. Eaton’s selectivity and coordination guide explicitly calls for evaluating the circuit-breaker, residual-current and AFDD functions separately in its combined device.
| Design input | Field to specify or verify | Rozhodnutí o výběru |
|---|---|---|
| Uspořádání napájení | Rated voltage, frequency and supported circuit configuration | Reject a device not declared for the supply |
| Design load and conductor capacity | Rated current and applicable derating | Protect the conductor while serving the intended load |
| Starting current and fault-loop conditions | B/C or other declared overcurrent characteristic | Check both normal inrush and required fault disconnection |
| Expected residual-current waveform | RCD type | Match the load electronics and applicable installation requirements |
| Required residual protection | Jmenovitý reziduální pracovní proud, IΔn | Choose sensitivity and coordination appropriate to the circuit |
| Předpokládaný zkratový proud | Breaking capacity and any documented backup arrangement | Verify adequate interruption at the installation point |
| Neutral and isolation requirements | Pole configuration and declared switching behavior | Confirm which conductors are switched and protected |
| Distribution-board construction | Device series, busbar, terminals, dimensions and thermal conditions | Verify assembly compatibility, not just physical fit |
| Destination market and application | Instructions, declarations and applicable certificates | Match documents to the exact ordered variant |
Rated Current Is Not Breaking Capacity
The current in amperes identifies the device’s rated load-current capability under declared conditions. Breaking capacity in kiloamperes describes its ability to interrupt a short circuit under the applicable test conditions. A larger ampere rating does not solve inadequate breaking capacity.
For a conventional overload-protection check, the circuit designer normally checks the relationship below, together with the applicable operating-current and installation requirements:
IB ≤ In ≤ Iz
IB = circuit design current
In = protective device rated current
Iz = conductor current-carrying capacity after applicable correctionsThis relationship alone does not complete cable sizing or protection coordination. Installation method, grouping, temperature, disconnection conditions and fault energy also matter. The Schneider guide to protective-scheme values explains the overload-protection conditions.
B/C Curve and Type A Are Different Classifications
A label such as “C16, Type A, 30 mA” contains four separate parameters. C identifies the overcurrent curve, 16 A is the rated current, and Type A identifies the residual-current waveform capability. The 30 mA value is the rated residual operating current.
Choosing a C curve does not change Type A into another residual-current type. Likewise, a B-curve breaker is not automatically a Type B RCD. Circuit-breaker and RCD terminology must be read separately.
The curves and waveforms above are conceptual illustrations, not model-specific time-current data or test waveforms.
Type A covers sinusoidal AC and pulsating DC residual currents within its specified conditions. It should not be assumed suitable for every load that can produce smooth DC or complex residual waveforms. Check the equipment instructions and installation requirements when choosing the residual-current function. Schneider guide to RCD types
For the overcurrent curve, consider startup current and the available fault current together. Changing the curve simply to stop unwanted trips can undermine the required disconnection performance. Consult the exact time-current data.
Check the Neutral Arrangement and Board Interface
Pole count and module width describe different things. A compact device may have a 1P+N configuration; its width does not tell you which pole has overcurrent protection or how the neutral is switched.
Read the device diagram and assembly instructions. Confirm neutral connections, permitted supply direction, busbar interface and the declared board/device combination. Do not infer these details from a front photograph or from another brand’s terminal layout.
Na stránkách Schneider circuit-breaker selection guide identifies installation characteristics, environment and loads as selection inputs. For an AFDD RCBO, those checks apply alongside its additional detection functions.
A Worked Specification Check
The following is a hypothetical screening example, not a completed installation design. Assume a designer has already established a 240 V AC, 50 Hz final circuit with a design current of 18 A and a corrected conductor capacity of 25 A. Assume the project requires Type A, 30 mA residual protection and the prospective short-circuit current at the device is 4 kA.
| Screening item | Example assessment | What remains to verify |
|---|---|---|
| Jmenovitý proud | A 20 A candidate satisfies 18 A ≤ 20 A ≤ 25 A | Full overload and conductor-protection conditions |
| Vypínací schopnost | A device declared at 6 kA for the applicable voltage and standard exceeds the assumed 4 kA | Actual fault assessment and any coordination requirements |
| Residual protection | Type A, 30 mA matches the stated design requirement | Suitability for the actual connected equipment and upstream protection |
| Nadproudová charakteristika | B or C cannot be selected from load current alone | Inrush and fault-disconnection checks |
| Board compatibility | No decision can be made from these electrical values alone | Approved interface, dimensions, neutral arrangement and thermal conditions |
The result is a candidate specification: 240 V AC, 50 Hz, 20 A, Type A, 30 mA, with sufficient declared breaking capacity. It is still incomplete until the curve, board interface and remaining design checks are resolved. This is why quoting only “20 A AFDD RCBO” leaves important choices unanswered.
Standards and Documents to Match to the Order
IEC/EN 62606 concerns the arc-detection device, while IEC/EN 61009-1 is relevant to the RCBO function. Their appearance in a catalog is not, by itself, proof of independent certification or permission to install the device in every jurisdiction.
Request the datasheet, installation instructions and declarations for the exact model and rating. Where the project requires a certificate, check its issuer, scope, covered variants and relevant standard edition. Product standards and local installation rules have different jobs; the IEC 62606 scope and evidence guide explains that distinction.
The documentation should also identify the test-button procedure and any diagnostic indications. A test button must be used according to the manufacturer’s instructions; its presence does not verify the complete installation or establish a universal field test for every protection function.
Applying the Selection to VIOX Devices
The current Produktová řada AFDD VIOX lists VAF1-40 and VAF3-40M as devices combining arc-fault, Type A residual-current, overload and short-circuit protection. The published range includes 6–40 A ratings, B/C characteristics and 10/30 mA residual sensitivities for 240 V AC, 50 Hz circuits, with a stated 1P+N configuration and 6 kA breaking rating.
VAF3-40M is described as the magnetic version. That name alone is not evidence of superior arc detection, different neutral behavior or a different installation method. Use the exact model documents to resolve construction details.
To request a suitable variant, send the supply details, design current, required curve, residual-current type and sensitivity, prospective fault current, board make/series, destination market and quantity to [email protected]. Include the required documentation and any OEM labeling requirements so the offered device can be checked against the complete specification.