Insights / Fire in Electrical Panels and Server Cabinets: The First Seconds

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Fire in Electrical Panels and Server Cabinets: The First Seconds

28 August 2026 · GRC Teknoloji · 9 min read

There may be no visible flame during the first stage of a fire in an electrical panel. Instead, there is a loose terminal, rising contact resistance, deteriorating cable insulation and smoke accumulating inside the enclosure. The critical part of the event often unfolds before the door is opened or anyone notices an odour.

Panel and server-cabinet fires therefore cannot be treated solely as a matter of fire response. Electrical protection, maintenance, early detection and local suppression must be designed as complementary layers.

How does a fire start inside a panel?

Arc faults fall into two principal categories:

A series arc occurs between two parts of the same conductor, typically because of conductor damage or a loose connection. It creates a local hot spot and can carbonise insulation.
A parallel arc occurs between different conductors after insulation failure.

A typical field scenario begins with a terminal that was not tightened sufficiently during installation or that became loose through thermal cycling. As connection resistance rises, heat generation at the contact point increases. Oxidation raises the resistance further and the process becomes self-reinforcing. Once carbonised insulation becomes conductive, the condition is no longer merely a maintenance finding; it has become an ignition source.

The Schneider Electric Electrical Installation Guide discusses series and parallel arc mechanisms and the use of AFDDs in greater detail.

When the temperature still looks “normal”

Under IEC 61439-1, temperature-rise limits are in the region of 70 K for terminals connected to external insulated conductors, 30 K for accessible metal enclosure surfaces and 40 K for insulating surfaces. In an ambient temperature of 35 °C, for example, interpreting a terminal measurement of 105 °C solely as an absolute value may be misleading.

Three data points should be considered together in a thermographic report:

The temperature rise permitted by the applicable standard,
The temperature difference from comparable adjacent connections under a similar load,
The trend at the same point over time.

A single thermal image taken under no load or light load may therefore conceal the actual behaviour of a hot spot. Wherever practicable, measurements should be repeated under comparable operating loads and retained as trend data.

The gap left by conventional protective devices

A thermal-magnetic circuit-breaker is not designed to recognise the characteristic waveform of an arc. A residual-current device responds to current flowing to earth. Arc current may remain below the short-circuit threshold of the breaker; if no earth-leakage current is present, the RCD may not operate either.

An arc fault detection device—AFDD—is intended to address this gap by recognising the electrical signature of a hazardous arc. The relevant product requirements are defined by IEC 62606:2013 and its 2017/2022 amendments. The product standard defines the requirements for the device; it does not, by itself, mandate AFDD use in every installation.

The maximum break times given in BEAMA’s AFDD fact sheet decrease as the arc current rises:

Arc current	Maximum break time
2.5 A	1 s
5 A	0.5 s
10 A	0.25 s
16 A	0.15 s
32 A and 63 A	0.12 s

In the example calculation used in the same technical note, an arc voltage of approximately 40 V and a current of 2.5 A correspond to about 100 W. With an assumed ignition energy of approximately 100 J, the critical threshold could be reached within one second. The point is not that these figures will be identical in every incident, but that even a seemingly low arc current can create a local ignition source very quickly.

How do current standards address internal arc faults?

IEC 60364-4-42:2024 addresses protection against thermal effects in low-voltage installations. The fourth edition, published on 22 November 2024:

Expanded the former Subclause 421.7 and moved it to Clause 426,
Added Clause 425 for protection against fire caused by fault currents,
Added Clause 427 for protection against internal arc faults in assemblies.

New specifications should therefore not simply repeat the former “421.7” reference; the scope of Clauses 426 and 427 in the 2024 edition should be considered explicitly.

The technical reference for internal arc-fault protection has also changed. IEC TS 61641:2026 was published on 19 August 2026 and replaces IEC TR 61641:2014 and IEC TS 63107:2020. It addresses internal arc-fault protection for low-voltage switchgear and controlgear assemblies in accordance with the IEC 61439 series.

How early can a server cabinet fire be detected?

NFPA 75 is the principal reference for protecting information technology equipment against fire and the associated effects of smoke, corrosion, heat and water. NFPA 76 applies to telecommunications facilities. Their scopes should not be treated as interchangeable.

Very early warning fire detection evaluates smoke in terms of obscuration. Design references use an alert threshold around 0.2 %/ft and an alarm threshold around 1.0 %/ft for VEWFD, while conventional point detectors may respond at higher smoke concentrations.

In full-scale tests simulating slow overheating inside electrical enclosures, aspirating smoke detection systems provided warnings hundreds of seconds before ionisation-type point detectors (U.S. NRC, ML15068A437). That interval can be valuable for investigating the event or activating an automatic protection layer.

EN 54-20:2006 divides aspirating smoke detectors into three sensitivity classes. Class B solutions are considered for effective early detection within critical equipment. The fact that two systems carry the same class designation, however, does not mean that their pipework, sampling and coverage performance will be identical.

Air movement also has a direct effect on detection design. In server rooms with high air-change rates, a small number of ceiling-mounted point detectors may not provide the expected early warning because smoke is diluted and transported by the airflow. Detector layout should be designed around the actual airflow and air changes per hour.

Choosing the correct suppression standard for a small enclosure

A common product-assessment error is to evaluate condensed aerosol products and clean-agent gaseous systems under the same family of standards.

Technology	Relevant standards
Clean-agent gaseous suppression	NFPA 2001, ISO 14520
Condensed aerosol suppression	NFPA 2010, EN 15276

The declared technology and cited standard should correspond. Statements such as “leaves no residue” or “does not damage electronics” should be treated as technical claims only when supported by independent, product-specific test evidence.

In Türkiye, the principal regulatory framework is the Regulation on Fire Protection of Buildings. Requirements concerning electrical installations, detection and alarm, periodic testing and maintenance, and fixed automatic suppression should be considered together. Rather than looking for a single clause dedicated to server rooms or data centres, the design should address the facility’s use, continuity requirements and equipment risks as a whole.

Protection layers before human intervention

According to Istanbul Fire Department statistics for 2019–2023, the average response time to a fire in Istanbul was 6 minutes and 40 seconds in 2023. Electrical deterioration inside a panel can progress on a scale of seconds.

This difference shows why protection cannot be left solely to human intervention. Automatic protective measures do not all operate at the same stage, however. The event and protection chain for a critical enclosure should be considered in this order:

Correct connections and documented maintenance,
Appropriate protection that recognises the electrical signature of an arc and safely disconnects power,
Early detection that monitors insulation deterioration and smoke,
Local or total-flooding suppression that operates after ignition.

These layers are not interchangeable. An AFDD is not a fire extinguisher, and a heat-activated extinguisher is not an arc-detection device. Autonomous units installed inside an enclosure form a local, post-ignition layer. They protect an enclosed volume within their declared limits, not the room; room-scale risk still requires a separately designed detection and suppression system.

A local post-ignition layer: MicroFireX

MicroFireX is an extinguishing device developed for installation inside electrical panels and similar small enclosures. It has two activation paths: automatic activation at a declared temperature of 170 °C without an external power connection, and manual activation through suitable simple triggering hardware.

The 170 °C value cannot be equated directly with the measured temperature of an arc or hot spot. The time required for the automatic trigger to reach this temperature depends on its position relative to the fault, enclosure geometry, obstructions, ventilation and the movement of hot gases. Automatic activation should therefore not be assumed to occur as soon as an arc forms or while the insulation is merely overheating. Its purpose is not to prevent or detect an arc, but to discharge extinguishing agent inside the enclosure after ignition or flaming has produced sufficient heat at the trigger location.

Manual activation does not depend on this thermal delay and may allow the device to be discharged earlier through suitable triggering hardware. It still depends on the event being detected, operator availability and a defined intervention procedure. It should therefore be assessed as a separate activation path, not as an equivalent to automatic thermal activation or early detection.

This boundary is important. MicroFireX does not replace correct panel design, connection maintenance, AFDD assessment, early smoke detection or a room-scale suppression system. It is an additional local line of defence intended to limit propagation beyond the enclosure after ignition. Suitability depends not only on enclosure volume but also on mounting position and the manufacturer’s application conditions.

Review the available models, protected volumes and technical limits for your panel or server cabinet: visit the MicroFireX product page →

A practical checklist

Verify terminal-tightening torques in critical panels against the manufacturer’s values and keep dated records.
Interpret thermographic reports using adjacent-connection differences and trends, not absolute temperature alone.
Repeat thermal imaging under real and comparable load conditions.
For new installations and alterations, assess AFDD requirements with reference to Clauses 426 and 427 of IEC 60364-4-42:2024.
Size server-room detection around the actual airflow and air changes per hour.
Consider EN 54-20 Class B solutions for early detection inside cabinets, evaluating test and coverage data rather than the class label alone.
Define in writing who acts—and how—at the alert and alarm stages.
Verify that the suppression technology matches the cited standards: NFPA 2010 / EN 15276 for aerosol; NFPA 2001 / ISO 14520 for clean agents.
Track service life and inspection of enclosure-mounted extinguishing devices in the asset register.
Retain periodic test, maintenance and intervention records in an auditable form.