Glossary · Lightning, earthing, fire safety
Combustible roofs and PV cables
NAPB forbids external wiring over combustible roofs; on bitumen shingle or onduline, DC cables run in metal trays or conduit.
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Definition
The Fire Safety Rules of Ukraine, NAPB A.01.001-2014 (section IV, ch. 1, cl. 1.18), forbid external wiring over combustible roofs. PV cables on a roof are external wiring, so on a roof of combustible materials (bitumen shingle on OSB, onduline and the like) they cannot simply lie on the covering.
The rule does not explain exactly how it applies to cables under an array. The practical answer is metal trays or conduit and penetrations of non-combustible materials. Whether your roof is combustible is set by the combustibility group of its surface layer on the maker’s certificate; the groups are classified in DBN V.1.1-7:2016 (Annex A). Do not guess the group from the material name.
Ukrainian norms set no fire setbacks from roof edges, no access paths between arrays, no mandatory rapid shutdown and no firefighter signage for rooftop PV. SES guidelines recommend a diagram showing the disconnection point placed near it, but that is a recommendation. What remains mandatory are the rules on penetrations, on wiring over combustible roofs and on lightning protection by risk assessment.
What it looks like in practice. On a soft roof or onduline, the cable from the string to the descent runs in a metal tray or metal conduit, and the cable entry under the roof goes through a penetration of non-combustible materials. Think separately about where the inverter and DC combiner go: NAPB (section IV, ch. 1, cl. 1.18) forbids storing combustible materials closer than 1 m to electrical equipment and under switchboards. The Solispec pitched-roof attachment calculator takes the covering into account for the fixings, and the fire warnings appear in the constructor's full report.
How Solispec applies it
You choose the roof covering in the Solispec constructor. For combustible coverings the engine shows a warning citing NAPB: run DC cables in metal trays or conduit, not on the roof; penetrations of non-combustible materials; check the combustibility group against the certificate (DBN V.1.1-7:2016 Annex A). The engine adds no fire setbacks: wind and structural edge distances are in the calculation, fire setbacks are set by no norm.
Norms and clauses
- NAPB A.01.001-2014, section IV, ch. 1, cl. 1.18
- DBN V.1.1-7:2016, Annex A
Related terms
- Fire-rated cable penetrationThe seal where a PV cable passes through a fire-rated wall or floor; its rating must be no lower than that of the construction.
- PV DC cableThe cable between the panels and the inverter; its section is chosen by I_SC MAX at 70 °C and checked for voltage drop.
- Lightning risk assessmentThe DSTU EN 62305-2:2022 calculation deciding whether a building with PV needs external lightning protection; there is no "PV means LPS" rule.
- PV earthing and equipotential bondingConnecting PV frames, rails and structures to the building’s earthing; under PUE:2026 the earthing must be common with the building.
- DBN V.2.5-23:2025 (from 01.01.2026): what applies to solarNorms explained
Solispec’s calculation is preliminary: for a design it has to be checked by an engineer. The values and clauses follow the current editions of the norms on the date of the page.