Fire-rated cable penetration

The cable from the panels to the inverter often passes through an attic floor or a wall. If that construction has a required fire resistance, the hole around the cable must not become a path for fire and smoke. DBN V.1.1-7:2016 (cl. 6.20) requires the penetration’s EI rating to be no lower than that of the construction itself.

DBN V.2.5-23:2025 (cl. 7.62) adds for wiring: EI or E rated penetrations tested to the relevant standard, and no cables in sleeves or trunking of combustible materials at such points. Clauses 7.53 and 7.54 of the same DBN forbid risers inside stairwells and open cable runs through stairwells. For PV on an apartment block this means the DC or AC route cannot run through a stairwell.

In practice the penetration is made with a certified system (collar, foam or mastic with a test report), not with ordinary expanding foam. For a house with a timber floor, also think about a combustible roof and where the cable exits onto the roof.

When this applies to a house. Floors and walls of a private house do not always have a required fire resistance, and then the cl. 6.20 penetration rules formally do not apply. But a boiler room, a garage or a fire wall between parts of the house are usually rated. Find the construction's rating in the building design. For PV on an apartment or public building, the cable route should appear in the design with the type of each penetration. Remember the combustible roof too, and the DC cable, which stays live even when the inverter is switched off.

The Solispec constructor has a "route passes through fire-rated constructions" flag. When it is on, the report adds the requirement: EI (E) penetrations no lower than the construction’s rating, not in combustible sleeves or trunking (DBN V.1.1-7:2016 cl. 6.20; DBN V.2.5-23:2025 cl. 7.62), and reminds you not to route through stairwells (cl. 7.53, 7.54).

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