Cable Fire Classes (CPR) and Fire Safety in Switchboards
cable fire class: The cable fire class is the CPR Euroclass system that describes how much a cable contributes to a fire; classes run from Aca to Fca with increasing contribution and are declared together with smoke (s), flaming droplet (d) and acidity (a) sub-classes. On the panel side, segregation of the cable compartment, penetration sealing and limiting the internal fire load are decisive.
Contents
Most fire damage in a building comes not from the flame itself but from smoke, corrosive gases and flame travelling along cable routes. The CPR classification under the Construction Products Regulation makes that behaviour measurable and lets it be expressed in a specification by a single code. This article covers the Euroclass system, the smoke and flaming droplet sub-classes, the difference between halogen-free and fire-resistant cables, and the measures needed where cables enter a switchboard.
What are CPR and the Euroclass system?
The Construction Products Regulation treats cables permanently installed in buildings as construction products and requires their reaction to fire performance to be declared. Classification runs from Aca to Fca: Aca covers cables that contribute virtually nothing to combustion, while Fca denotes cables for which no performance has been declared. The intermediate classes B1ca, B2ca, Cca, Dca and Eca are separated by measured quantities such as flame spread, heat release rate and total heat release. The declaration of performance and CE marking must be traceable on the drum and in the delivery documents; writing the class as well as the cable type into the specification is the simplest measure that prevents incorrect supply.
Smoke, flaming droplet and acidity sub-classes
Three sub-classifications are declared in addition to the main class. Smoke production is graded s1, s2 and s3, where s1 denotes the lowest smoke performance and is critical in escape corridors. Flaming droplets are expressed as d0, d1 and d2, where d0 means no flaming droplets occur and prevents fire being carried down a vertical shaft. Acidity is classified a1, a2 and a3 and describes the corrosive effect of combustion products; a1 is preferred where electronic equipment is installed, because acidic gases continue to damage boards and contacts after the fire is out. A specification remains incomplete unless it states these three sub-classes together with the main class.
Are halogen-free and fire-resistant cables the same thing?
No, and this is the most frequently confused pair of concepts in the field. A halogen-free cable does not produce corrosive and toxic halogenated gases when burning; its purpose is to improve evacuation and equipment protection, but it does not mean the circuit keeps working during a fire. A fire-resistant cable is declared to maintain circuit integrity for a defined period and is used in circuits that must operate during a fire: smoke extraction fans, fire pumps, emergency lighting and fire detection circuits. In one installation both properties may be needed in different circuits and sometimes in the same cable; the choice follows the role of the circuit in the fire scenario.
Fire safety on the panel side
| Class or sub-class | Meaning | Typical use |
|---|---|---|
| B2ca | Very limited flame spread and heat release | Escape routes, assembly areas, high-rise buildings |
| Cca | Limited flame spread and heat release | General building installation, commercial areas |
| Dca and Eca | Higher contribution to combustion | Technical spaces and low risk areas |
| s1 | Lowest smoke production | Escape corridors and enclosed car parks |
| d0 | No flaming droplets occur | Vertical shafts and floor penetrations |
| a1 | Least corrosive combustion products | Data centres and rooms with electronic equipment |
The cable bundle arriving at a board is part of the design in terms of both fire load and propagation path. Separating the cable compartment from the functional compartments limits the spread of an event caused by a cable fault, and barrier walls and cable entry plates determine how effective that separation is. Where cables cross between fire compartments, penetration sealing must use a system matched to the fire resistance period of the wall and must be reinstated for every cable added later; a penetration left open cancels the entire function of the wall. Using halogen-free cable and flame-retardant cable trunking inside the panel noticeably reduces damage after an internal arc or overheating event.
Selection, specification and documentation
A good specification differentiates the cable class by location: low smoke and flaming droplet performance for escape routes and assembly areas, more flexible classes for technical spaces, and a separate circuit integrity declaration for circuits that must operate during a fire. At procurement the declaration of performance should be checked and drum labels recorded. The commissioning file should contain the classes of the cables used and the documentation of the penetration sealing systems, which also makes selecting the right material easier during later alterations. When the fire scenario of a building changes, for example when a space becomes an escape route, the existing cable classes must be reassessed.
Key takeaways: cable fire class
- State the CPR class explicitly in the specification — add the smoke, droplet and acidity sub-classes next to the main class.
- A halogen-free cable is not a fire-resistant cable — one targets gas emission, the other circuit integrity.
- Seal penetrations to match the fire rating of the wall — reinstate the seal for every cable added later.
- Cable compartment segregation limits propagation — barrier walls and entry plates are part of the design.
- Standard source — IEC publication catalogue: iec.ch.
Frequently asked questions
If I use halogen-free cable, do I still need fire-resistant cable?
Yes. The halogen-free property reduces corrosive and toxic gas emission during burning but does not guarantee that the circuit keeps working. For circuits that must operate during a fire, a cable with a declared circuit integrity performance must be selected separately.
Do I have to upgrade the cable class in an existing building?
As a rule, newly installed and refurbished sections follow current requirements. Wholesale replacement of an existing installation is not usually required, but when the use of a space changes or the definition of an escape route is updated, the relevant route has to be reassessed.
Which cable should be used inside the panel?
Halogen-free and flame-retardant types are preferred for internal panel wiring, since they reduce smoke and corrosion damage after an internal arc or overheating. It is also a detail worth assessing alongside the cable that the trunking and cable ties are flame retardant.
Related articles
- Cable Zone and Cable Entry Design: Common Switchboard Mistakes
- Cable Sizing and Voltage Drop Calculation
- Internal Arc Withstand and Arc Protection: What IEC 61641 Adds
- ATEX Panels: The Ex d and Ex e Protection Concepts
- All technical articles
In Devpan boards internal wiring, cable compartment segregation and entry plate arrangement are designed with fire safety requirements in mind. Contact our engineering team for a cable and panel interface matched to the fire scenario of your project. Related Devpan solution: electrical panel design services.
