A loose connection in a junction box. A cable drilled into when a wall was fitted out. A conductor that has been kinked behind a cupboard for years.
None of that shows up in everyday use. No circuit breaker trips. No residual current device reacts.
And yet that is exactly where a fire can start.
The reason is called an arc fault. And it is why fire protection in electrical installations today demands more than correctly sized cables. In this article I show what the standards require, where misunderstandings often arise, and why initial verification is the decisive moment.
Three standards, one goal: safe installations
DIN VDE 0100 is the fundamental set of rules for erecting low-voltage installations. Three of its parts are especially important for safety and fire protection:
- DIN VDE 0100-410: Protection against electric shock. Among other things it covers additional protection by residual current devices (RCD).
- DIN VDE 0100-420: Protection against thermal effects. This is about fire protection, including protection against arc faults.
- DIN VDE 0100-600: Initial verification. It defines how an installation is tested and documented before commissioning.
Each of these standards covers a different aspect. Together they form a chain — and a chain is only as strong as its weakest link.
Arc faults: the gap in the classic protection concept
Circuit breakers protect against overload and short circuit. Residual current devices protect against earth fault currents. Both are indispensable.
Neither detects a serial arc fault. It can form, for example, at a loose terminal or a damaged conductor. Current still flows, but high temperatures develop at the fault. Over time surrounding material can catch fire.
This is exactly where arc fault detection devices come in — also called AFDD (Arc Fault Detection Device). They analyse the current waveform and disconnect when they recognise the typical pattern of an arc fault.
Obligation or recommendation? What DIN VDE 0100-420 really requires
Few topics have been debated as fiercely in the industry. The 2016 edition caused a lot of uncertainty. The current edition DIN VDE 0100-420:2019-10 thoroughly revised the section on arc faults.
The core in one sentence: arc fault detection devices are recommended, but not required across the board.
What the standard does require is a risk and safety assessment. Designers or installers, together with the operator, judge which fire risks exist. From that follow structural, installation or organisational measures. The AFDD is one possible installation measure.
It is recommended among other things for:
- Rooms with sleeping accommodation
- Rooms with a particular fire risk
- Rooms with components of combustible building materials, for example in timber construction
- Places where irreplaceable goods are at risk
That sounds like latitude. In truth it is responsibility. Anyone who forgoes a measure must be able to justify why the risk is acceptable. That justification belongs in the design documentation.
Initial verification: the moment of truth
The best design is of little use if execution does not match it. That is why DIN VDE 0100-600 requires an initial verification before commissioning. It has three steps:
- Inspection: Does the installation match the design? Are equipment correctly selected, cables correctly installed, firestopping properly executed?
- Testing: Do protective devices, emergency stop and safety functions work as intended?
- Measuring: Insulation resistance, continuity of protective conductors, loop impedance, RCD trip conditions.
At the end stands a test report. It is not mere paperwork. It is the proof that the installation is safe. For clients and operators it is also the basis for acceptance, warranty and insurance.
In practice I see two typical weaknesses. First: testing under time pressure shortly before handover, when defects can barely be fixed without delay. Second: the report is complete, but the inspection was superficial — yet inspection is exactly what reveals faults no instrument finds.
What this means for your project
Fire protection in the electrical installation does not begin at testing. It begins in design. Three recommendations from my practice:
- Carry out the risk assessment early. Ideally in design development (LPH 3 / HOAI work stage 3), together with the client and the fire protection planner. Then the results feed into cost and distribution-board design.
- Document decisions. Why an AFDD here, why not there? A clear rationale protects everyone involved.
- Build verification into site supervision. Initial verification to DIN VDE 0100-600 needs time in the construction programme — with buffer for defect rectification.
I know these topics from three angles. As an electrician I erected installations and hunted faults in complex systems. As a project engineer I design to DIN VDE 0100-410, -420 and -600. And as a client representative I know how important clean documentation is at acceptance.
Conclusion
Most electrical fires can be avoided — not by a single device, but by a chain: sound risk assessment, considered design, clean execution and a thorough initial verification.
Anyone who leaves out one of those links is cutting the wrong corner.
Want to set up fire protection and verification correctly from the start in your project, or need support with site supervision and acceptance? Let’s talk.
Note: This article gives an overview and replaces neither the standards nor project-specific design.
Source: Forum Verlag, Sind Brandschutzschalter Pflicht?