Documentation
Fusebox Diagram Reference
Device abbreviations, single- and three-phase conductor colours per HD 308 S2, RCD types, RCD grouping conventions and circuit schedule columns for documenting a distribution board. Use alongside the Fusebox Diagram Generator.
Last updated: July 2026
Terms
- HD 60364Harmonization Document 60364
- The European adaptation of the international IEC 60364 wiring rules — most EU countries base their national electrical installation regulations on this document.
- IECInternational Electrotechnical Commission
- The international body that writes electrical safety standards used across most of the world outside North America. When a chart cites an IEC number, it's pointing to the official rulebook behind a calculation.
- MCBMiniature Circuit Breaker
- The switch in a fuse box that automatically trips (switches off) if a circuit draws too much current, protecting the wiring from overheating. It can be reset and reused, unlike a traditional fuse.
- RCBOResidual Current Breaker with Overcurrent Protection
- A single device that combines an MCB and an RCD — it protects a circuit both from overload/short-circuit and from earth leakage, in one unit per circuit instead of sharing one RCD across many.
- RCDResidual Current Device
- A safety switch that instantly cuts power if it detects electricity leaking to earth — for example through a person or a faulty appliance — protecting against electric shock.
- VDEVerband der Elektrotechnik Elektronik Informationstechnik
- The German electrical engineering association that publishes widely-used safety standards in Germany and beyond — similar in role to IEC, but specifically German.
Device Abbreviations
Common abbreviations used on single-line distribution board diagrams and circuit schedules.
| Abbreviation | Device | Typical rating format | Function |
|---|---|---|---|
| Main | Main switch / incomer | e.g. 40A, 63A | Isolates the whole board |
| RCD | Residual-current device | e.g. 40A/0.03A | Earth-fault (shock) protection for a group of circuits |
| RCBO | Combined RCD + MCB | e.g. B16/0.03A | Earth-fault and overcurrent protection for a single circuit |
| MCB | Miniature circuit breaker | e.g. B16, C32 | Overcurrent/short-circuit protection for one circuit |
| AFDD | Arc fault detection device (Brandschutzschalter) | e.g. B16 | Detects dangerous arc faults — fire protection per IEC 60364-4-42 / DIN VDE 0100-420 |
| SPD | Surge protective device | e.g. Type 2 | Limits transient overvoltage from lightning/switching |
| Reserve | Spare way | — | Unused space reserved for a future circuit |
Conductor Colour Coding (HD 308 S2)
Harmonised conductor identification colours per HD 308 S2, as used across the diagram's busbar, tap wires and PE rail. Single-phase boards use L1 (brown) only; three-phase boards use all three line colours.
| Conductor | Colour | Swatch |
|---|---|---|
| L1 (Line 1) | Brown | |
| L2 (Line 2) | Black | |
| L3 (Line 3) | Grey | |
| N (Neutral) | Blue | |
| PE (Protective Earth) | Green/Yellow stripe |
Older installations (pre-harmonisation) may use different phase colours — always verify colours on-site rather than assuming from a diagram alone.
RCD Types (EN 61008 / EN 61009)
Which fault-current waveforms an RCD can detect. Informational only — the required type is a design decision for a qualified electrician.
| Type | Detects | Typical use |
|---|---|---|
| AC | Sinusoidal AC fault currents only | Legacy — should no longer be specified for new installations with electronic loads |
| A | AC + pulsating DC fault currents | The modern minimum for most household/commercial circuits |
| F | Type A + mixed-frequency fault currents | Circuits with frequency inverters (heat pumps, washing machines, AC units) |
| B | Type F + smooth DC fault currents | EV chargers, PV inverters, variable-frequency drives |
RCD Grouping — Common Conventions
General conventions seen in practice when splitting circuits across multiple RCDs. These are background context, not a substitute for a qualified electrician's design decisions.
| Convention | Rationale |
|---|---|
| Separate lighting from sockets | An earth fault on a socket circuit doesn't also drop room lighting |
| Separate wet areas (bath/kitchen) | Higher fault-risk areas isolated from the rest of the installation |
| Split large boards across 2+ RCDs | A single nuisance trip doesn't de-energise the entire property |
| Dedicated RCBO for sensitive loads | Isolates one circuit (e.g. freezer, server) from unrelated trips |
Circuit Schedule Columns (Stromkreisliste)
Standard columns used in the printed circuit schedule beneath the diagram.
| Column | Meaning |
|---|---|
| Nr. | Auto-numbered circuit index (MCB/RCBO/AFDD rows only) |
| Gerät / Typ | Protective device type (MCB, RCBO, AFDD, RCD incl. type, SPD, Main, Reserve) |
| Phase | Assigned phase on three-phase boards — L1, L2, L3, or 3~ for multi-pole devices |
| Nennstrom | Rated current / trip curve, e.g. B16, C32 |
| Kabel | Cable type and cross-section, e.g. NYM-J 3×1.5 |
| Bezeichnung | What the circuit feeds — room or load description |
| RCD-Gruppe | Which RCD this circuit sits under, or "—" if direct from the busbar |
Worked Example — Sample Schedule
A small single-phase board with two RCD groups and one direct circuit, as it would appear in the generated schedule.
| Nr. | Gerät / Typ | Nennstrom | Kabel | Bezeichnung | RCD-Gruppe |
|---|---|---|---|---|---|
| — | Main switch | 40A | — | Main switch | — |
| 1 | MCB | B16 | NYM-J 3×1.5 | Living room sockets | RCD 1 |
| 2 | MCB | B16 | NYM-J 3×1.5 | Lighting | RCD 1 |
| 3 | MCB | B32 | NYM-J 3×2.5 | Kitchen — oven | RCD 2 |
| 4 | MCB | B16 | NYM-J 3×1.5 | Garage (direct) | — |
Frequently Asked Questions
Does this reference chart tell me how to design my distribution board?
No — it's background context on abbreviations, colours and common conventions used when documenting a board that has already been designed. Actual circuit design, protection coordination, RCD/AFDD requirements and RCD grouping decisions must be made by a qualified electrician (Elektrofachkraft) per the applicable national standard based on IEC 60364 / HD 60364 (e.g. DIN VDE 0100 in Germany).
Why does the schedule leave the Nr. column blank for some rows?
Only MCB, RCBO and AFDD rows feed a load directly, so only they get an auto-incrementing circuit number. Main, RCD, SPD and reserve rows organise or protect the board itself rather than feeding an individual circuit.
Aren't black and grey conductors a sign of old wiring?
Not on three-phase installations — under HD 308 S2, black and grey are the current standard colours for L2 and L3, alongside brown for L1. On old single-phase wiring, however, black or grey line conductors can indicate pre-harmonisation colours — always verify actual conductor colours on-site rather than relying on a diagram alone.