A lightning protection installer or electrician regularly faces the same question: what lightning protection level (NPF) should I apply to this building?
The complete regulatory answer is found in the IEC 62305-2 risk assessment — a rigorous but often cumbersome process reserved for engineering firms handling complex structures. For the vast majority of standard buildings, there is a more direct route: the simplified FD C 17-108:2017 method, now integrated into LPS Manager.
In this article, discover how this method works, when to use it, and how LPS Manager allows you to determine the NPF in just a few minutes directly on site.
NPF, IEC 62305 and FD C 17-108: what are we talking about?
Before diving into the method, a few essential definitions:
- NPF (Lightning Protection Level): classification from I to IV defining the required robustness of the protection system. NPF I is the most demanding, NPF IV the least constraining.
- IEC 62305-2: international standard defining the complete method for assessing lightning risk for any structure.
- FD C 17-108:2017: documentation fascicle (non-binding but professionally recognized) proposing a simplified method based on IEC 62305-2, applicable to standard structures without exceptional risk.
The FD C 17-108 method covers approximately 90% of common structures: tertiary buildings, warehouses, residential buildings, industrial buildings with ordinary fire risk. It is not applicable to ATEX sites, explosive structures or particularly complex structures.
The FD C 17-108 method in 5 steps
The simplified method revolves around five key parameters:
Step 1 — Determine the Nsg of the site
The Nsg (lightning density in the air, in strikes/km²/year) is the fundamental parameter. It varies according to geographic location: from less than 1 strike/km²/year in Northern Europe to more than 10 strikes/km²/year in some tropical regions.
In LPS Manager, Nsg is automatically populated as soon as you geolocate the building on the map — no manual entry, no isokéraunic map consultation.
Step 2 — Characterize the structure
A few simple parameters are sufficient:
- Building dimensions (length, width, height)
- Roof type (metal, concrete, tiles)
- Isolated or not
- Presence of protruding structures (antennas, chimneys)
Step 3 — Assess the type of potential losses
The FD C 17-108 method distinguishes:
- Loss of human life (L1) — most critical risk
- Loss of public service (L2)
- Loss of cultural heritage (L3)
- Economic losses (L4)
For most common buildings, L1 and L4 are the only losses to consider, which greatly simplifies the analysis.
Step 4 — Calculate the expected annual impact frequency
From the Nsg and building dimensions, we calculate Nd (number of dangerous lightning strikes per year). If Nd exceeds the acceptable threshold Nc (defined by the type of acceptable losses), protection is necessary.
LPS Manager performs this calculation automatically and clearly displays the result: protection necessary or not, and if yes, which NPF.
Step 5 — Determine the required NPF
The determined NPF (I, II, III or IV) determines:
- The protection radius of the lightning rod or the mesh of the lightning protection cabling
- The maximum admissible earth resistance
- The spacing of the down conductors
- The level of surge protectors to install (Class I, II or III)
LPS Manager: NPF calculation directly on site
Before LPS Manager, determining a building’s NPF involved either filling out a complex Excel spreadsheet at the office or calling on an engineering firm. LPS Manager puts this calculation in the installer’s pocket, accessible from a smartphone or tablet on the job site.
What LPS Manager does automatically
- Site geolocation → Automatic Nsg from the global database
- Guided form for building characteristics (simple format, adapted to field)
- Instant calculation: Nd, Nc, required NPF
- Exportable report in PDF with calculation data, transmissible to client or insurer
For which user profile?
LPS Manager Pro specifically targets:
- Lightning protection installers seeking to formalize and accelerate their field studies
- Electricians adding lightning protection to their service offering
- Maintenance managers wishing to verify the consistency of existing installations
It does not replace a specialized engineering firm for complex structures, ATEX sites or high-risk structures. But for 90% of common interventions, it provides an immediate, documented and compliant answer.
Concrete example: 5-story tertiary building in a moderately stormy zone
Let’s take a typical example (example values):
- Building: 30 m × 20 m × 18 m high, concrete roof, industrial zone
- Location: Brussels region (Belgium) — Nsg ≈ 1.5 strikes/km²/year
- Losses considered: L1 (persons) + L4 (economic)
LPS Manager calculates: Nd = 0.27 strikes/year, Nc = 0.1 (L1 threshold) → Protection necessary → NPF III recommended.
Result transmitted to client in 5 minutes, with PDF report to back it up. The installer can directly propose an NPF III Paraton@ir lightning rod with adapted protection radius from the LPS France catalog.
From field study to long-term management: LPS Manager supports the entire cycle
Determining the NPF is just the beginning. Once the installation is complete, LPS Manager allows you to:
- Record the installation with its characteristics and NPF
- Plan periodic maintenance (annual according to IEC 62305-3)
- Monitor lightning strikes via the Site Monitoring feature
- Generate compliance reports at any time
For installations equipped with a Contact@ir communication system, the connection with LPS Manager is direct: radio supervision data at 868 MHz automatically feeds into the platform.
Conclusion: the FD C 17-108 method accessible to all installers
Determining the lightning protection level is no longer reserved for engineering firms. With LPS Manager Pro and the integrated FD C 17-108 method, any installer can carry out this assessment on site, in just a few minutes, with a documented result compliant with IEC 62305.
It’s a direct competitive advantage: offer a quantified study to your client on the first visit, not a week later at the office.
Discover LPS Manager Pro and try the NPF calculation on your next job site.
