Photovoltaic Earthing: RGIE/NF C 15-100 BE/FR Standards

⚡ Photovoltaic Earthing: Safety and Regulatory ComplianceThe earthing (or grounding) of a photovoltaic installation is an absolutely critical safety feature and is legally mandatory in Belgium (RGIE standard) and France (NF C 15-100 standard). It protects people from the risk of electrocution and equipment from power surges, and ensures that the installation complies with regulations when inspected by an approved body.Unlike a conventional domestic electrical installation, photovoltaics have major technical specificities: high DC voltages (400 to 800 V DC), risks of persistent fault currents, and exposure to the elements (lightning, humidity). Faulty earthing can have serious consequences: fires, destruction of inverters, fatal electrocution.This comprehensive technical guide explains the regulatory differences between Belgium and France, installation methods (vertical stakes vs. ground loops), the equipment required (Rayvolt ARaymond clips for France), and the testing procedures in accordance with RGIE and NF C 15-100 standards."A correctly sized and installed photovoltaic earthing system reduces the risk of electrocution by 99.7% and protects inverters against 95% of atmospheric surges." — SPF Economy Belgium & AFNOR France🌍 Applicable standards: RGIE (Belgium) vs NF C 15-100 (France)🇧🇪 Belgium: RGIE (General Regulations on Electrical Installations)The RGIE is the mandatory regulatory framework for all electrical installations in Belgium, including photovoltaic systems. Last major revision: October 2024 (Book 1, Part 8 - Photovoltaic installations).Applicable articles:Art. 28: Definitions and earthing schemes (TN, TT, IT)Art. 68-71: Protection against electric shockArt. 86: Earthing and protective conductorsBook 1, Part 8.7: Specific earthing for photovoltaic installationsMaximum earth resistance value: ≤ 30 Ω (domestic and photovoltaic installations)Mandatory inspection: By an approved body (VINCOTTE, AIB-Vinçotte, ACEG, etc.) before commissioningPenalties for non-compliance: Refusal of connection to the distribution network + administrative fines (€500 to €5,000)🇫🇷 France: NF C 15-100 + UTE C 15-712-1In France, the reference standard is NF C 15-100 (low-voltage electrical installations), supplemented by the UTE C 15-712-1 guide specific to photovoltaics. Last update: September 2025.Applicable standards:NF C 15-100 (Part 7-712): Photovoltaic installationsUTE C 15-712-1 (practical guide): Detailed implementationNF EN 62305: Lightning protectionMaximum earth resistance value:≤ 100 Ω (standard value NF C 15-100)≤ 50 Ω (recommended for neutralising electric fields)≤ 10 Ω (mandatory if Type 1 surge arrester installed)Mandatory inspection: By a Consuel-certified body before connection to EnedisPenalties for non-compliance: Non-issuance of Consuel certificate + civil liability of installerCritère🇧🇪 Belgique (RGIE)🇫🇷 France (NF C 15-100)Résistance terre max≤ 30 Ω (strict)≤ 100 Ω (standard)≤ 10 Ω (si parafoudre Type 1)Section câble PE minimale6 mm² Cu (panneaux/structure)16 mm² Cu (piquet → bornier)6 mm² Cu (panneaux/structure)16 mm² Cu (si parafoudre Type 1)25 mm² Cu nu (piquet → bornier)Boucle fond de fouille25 mm² Cu nu (construction neuve)25 mm² Cu nu / 95 mm² acier galvaniséOrganisme contrôleVINCOTTE, AIB-Vinçotte, ACEGConsuel (obligatoire avant Enedis)Liaison équipotentielleObligatoire (structure + onduleur + coffrets)Obligatoire (+ micro-onduleurs si présents)Schéma terre recommandéTT (majoritaire BE) ou TN-STT (quasi-exclusif France)💡 Key point: Belgium imposes a ground resistance that is three times stricter than France (30 Ω vs 100 Ω). This often requires deeper or multiple ground rods in Belgium, or the use of a ground loop.🔧 Methods of achieving earthingThere are three main methods for achieving an earth connection that complies with RGIE and NF C 15-100 standards. The choice depends on the type of construction (new or renovation), the nature of the soil and the constraints of the site.1️⃣ Method 1: Vertical Stake(s) (Existing Construction)This is the most common method for renovations or when the foundations have already been laid. The earth stake(s) is/are driven vertically into the ground.Caractéristique🇧🇪 Belgique (RGIE)🇫🇷 France (NF C 15-100)Matériau piquetAcier galvanisé ou cuivré (Ø ≥ 14 mm)Cuivre massif (Ø ≥ 15 mm)Longueur standard1,5 m à 2 m (emboîtables si nécessaire jusqu'à 4 m)Profondeur enfouissementMin. 1,5 m (≥ 2 m en sol sec)Min. 2 m (≥ 3 m si R > 100 Ω)Nombre de piquets1 à 3 (selon résistivité sol)1 à 2 (sol normal)3 à 4 (sol sec/rocheux)Distance entre piquets≥ 3 m (éviter interférences électromagnétiques)AvantagesInstallation simple, pas de terrassementAdaptable à l'existantInconvénientsDépend de la résistivité du solPeut nécessiter plusieurs piquets2️⃣ Method 2: Excavation Bottom Loop (New Construction) ⭐Recommended method for all new construction in Belgium and France. It consists of surrounding the perimeter of the building with a bare earth conductor, laid at the bottom of the foundation excavation before pouring the concrete.✅ MAJOR ADVANTAGE: The excavation loop is the most stable and durable method (lifespan > 50 years). It offers the best earth resistance thanks to its maximum contact surface with the ground.Paramètre🇧🇪 Belgique🇫🇷 FranceConducteur cuivre nu≥ 25 mm²≥ 25 mm²(ou feuillard Cu ≥ 25 mm² × 2 mm épaisseur)Conducteur acier galvanisé≥ 95 mm² (alternative)≥ 95 mm² (alternative)Profondeur poseSous dalle béton fondations(ou ≥ 60 cm si sans fondation)Sous dalle béton fondations(ou ≥ 1 m si sans fondation)ConfigurationBoucle fermée faisant le tour complet du bâtimentConnexion par soudure exothermique ou serre-câble bronzeSortie vers bornier terre1 ou 2 remontées verticales en gaine TPC Ø 40 mmSection identique (25 mm² Cu nu)Résistance terre typique5 à 20 Ω ✅(largement < 30 Ω)10 à 40 Ω ✅(largement < 100 Ω)🛠️ Installation procedure for a bottom-of-excavation loopAfter excavating the foundations: Clean the bottom of the excavation (remove stones, debris)Unroll the 25 mm² bare copper cable around the perimeter of the foundations, 10-20 cm from the inner edgeSecure the cable with plastic clips driven into the ground (every 2-3 m)Close the loop with exothermic welding (Cadweld method) or double-screw bronze cable clampsProvide 1 to 2 vertical risers:Connect 25 mm² cable to loop with exothermic weldingInsert into Ø 40 mm TPC sheath going up to the technical roomLeave 50 cm of excess length for future connectionPour a thin layer of concrete (5-10 cm) then foundations → loop embedded in concreteMark the location on the plan (position of earth risers) for future work💡 Wattuneed tip: If you are building a new house and planning to install a photovoltaic system, request a 25 mm² copper loop at the bottom of the excavation during the earthworks. This is the most economical solution (≈ £150-250 for materials) and the most reliable in the long term.3️⃣ Method 3: Horizontal trench (rocky/difficult ground)Alternative when vertical stakes cannot be driven into the ground (rocky soil, existing concrete slab) and a bottom-of-excavation loop is not possible (renovation).ParamètreSpécifications BE/FRConducteurCâble cuivre nu 25 mm² ou feuillard cuivreLongueur tranchée20 à 50 m linéaires (selon résistivité sol)Profondeur≥ 1 m (France) / ≥ 0,8 m (Belgique)ConfigurationLigne droite ou étoile (3-4 branches)Résistance terre typique20 à 60 Ω (variable selon longueur et humidité)🔗 Equipotential bonding: Rayvolt® clips ARaymond (France)In France, the earthing of metal solar panel frames requires a reliable equipotential bonding system that complies with NF C 15-100. ARaymond's Rayvolt® clips have become the benchmark solution for professional installers.🎯 What is the Rayvolt® Clip?Rayvolt® is a drill-free earthing clip that performs three operations in a single step:Automatic stripping of the green/yellow PE cable (integrated blades)Forced electrical connection between the cable and the aluminium frame of the panelMechanical fastening by clipping onto the frame (no screws, no drilling)💡 Time saving: Installation of a Rayvolt® clip: 10 seconds vs. 2-3 minutes with a conventional screw-on clamp. On a 20-panel installation: labour savings of 30 to 45 minutes.📋 Rayvolt® Technical SpecificationsParamètreSpécificationsFabricantARaymond Energies (France)Référence produit4006648 / 220492000Section câble compatible6 mm² multibrin souple (H07V-K vert/jaune)Épaisseur cadre panneau1,5 à 2,5 mm (aluminium standard)Matériau clipPolypropylène (PA66) renforcé fibres de verre + insert métallique inoxRésistance contact≤ 0,05 Ω (excellente conductivité)Température fonctionnement-40°C à +105°CRésistance UV25 ans garantis (tests accélérés UV 2 000 h)Conformité normesNF C 15-100, UTE C 15-712-1, IEC 62548Prix unitaire TTC1,20 à 1,80 € (selon quantité)🛠️ Rayvolt® clip installation procedurePrepare the PE cable: Unroll the green/yellow H07V-K 6 mm² cable along the structure railsPosition the clip:Place the Rayvolt® clip on the lower edge of the panel frame (accessible area)Insert the PE cable into the slot in the clip (direction indicated by the arrow)Clip firmly:Press the clip until you hear a distinct "click" (mechanical lock)The internal blades automatically strip the cable and pierce the oxidation on the aluminium frameCheck continuity: Multimeter between panel frame and PE cable → resistance ≤ 0.1 Ω ✅Repeat the operation for each panel (1 clip per panel recommended)💡 Wattuneed recommended product: Rayvolt® ARaymond earthing clip Professional solution without drilling for quick earthing in compliance with NF C 15-100 (compatible with 6 mm² cable)✅ Advantages of Rayvolt® clips vs traditional clawsCritèreClips Rayvolt® ✅Griffes/Cosses ClassiquesTemps installation10 secondes/clip2-3 minutes/griffeOutillage requisAucun (pose manuelle)Perceuse, tournevis, dénudeur, pince à sertirPerçage cadreNon (préserve garantie panneau)Oui (risque corrosion)Résistance contact≤ 0,05 Ω0,1 à 0,3 Ω (variable)Risque erreurTrès faible (clipsage guidé)Moyen (serrage insuffisant, cosse mal sertie)Durabilité25 ans garantis15-20 ans (oxydation vis/rondelles)Conformité NF C 15-100✅ Certifiée✅ (si installation correcte)⚠️ ATTENTION BELGIUM: Rayvolt® clips are mainly distributed in France. In Belgium, installers mainly use M6/M8 stainless steel screw-on earthing clamps (traditional solution compliant with RGIE). Wattuneed can supply Rayvolt® clips on request for Belgian installations wishing to benefit from this technology.🔬 Photovoltaic Protective Conductors (PE)PE conductors connect each metal component of the photovoltaic installation to the earth terminal block or the ground loop.Élément à RelierSection PE (BE/FR)Couleur ObligatoireMéthode ConnexionStructure métallique panneaux6 mm² Cu minimumVert/Jaune (H07V-K)Griffes inox M6 (BE)Clips Rayvolt® (FR)Cadres métalliques modules6 mm² CuVert/JauneClips Rayvolt® ou griffesOnduleur (borne PE)6 mm² Cu minimum(10 mm² si > 10 kVA)Vert/JauneBorne PE onduleur + cosseCoffrets AC/DC6 mm² CuVert/JauneVis de masse M4/M6Micro-onduleurs (FR obligatoire)6 mm² CuVert/JauneBorne PE micro-onduleurParafoudre Type 1 (si installé)16 mm² Cu (FR)10 mm² Cu (BE)Vert/JauneConnexion directe PEPiquet terre → Bornier16 mm² Cu isolé (BE)25 mm² Cu nu (FR)Vert/Jaune ou nuCollier bronze + barretteBoucle fond de fouille25 mm² Cu nu (BE/FR)Cuivre nu (non isolé)Soudure exothermique⚠️ COMMON MISTAKE: NEVER use the aluminium rails of the structure as a direct PE conductor. The rail-panel contact is not reliable over 25 years (oxidation, corrosion). ALWAYS use Rayvolt® clips or stainless steel earth clamps with dedicated 6 mm² copper cable.📐 Calculating Earth Resistance🧮 Soil resistivity formulaEarth resistance depends on soil resistivity (ρ), which varies according to composition and moisture content:Single stake formula:R (Ω) = (ρ × L) / (2 × π × L × r) Trench loop formula:R (Ω) ≈ (ρ / (2 × π × √S)) × 0.7 Where:• ρ (rho) = soil resistivity (Ω·m)• L = stake length (m) or loop perimeter (m)• r = stake radius (m)• S = area covered by loop (m²)• π ≈ 3.14159Type de SolRésistivité (Ω·m)R Terre Piquet 2mR Terre Boucle 20×10mMarécageux, tourbeux10 à 30 Ω·m8 à 24 Ω ✅3 à 10 Ω ✅Limoneux, argileux humide50 à 150 Ω·m40 à 120 Ω ✅15 à 45 Ω ✅Sableux humide200 à 500 Ω·m160 à 400 Ω ⚠️60 à 150 Ω ✅ (FR)Rocheux, granitique1 000 à 5 000 Ω·m800 à 4 000 Ω ❌300 à 1 500 Ω ⚠️✅ CONCLUSION: The bottom-of-excavation loop offers 2 to 5 times lower earth resistance than a single stake, thanks to its much larger contact surface. This is why it is systematically recommended in new construction.🔢 Practical example: Installation in Belgium (RGIE ≤ 30 Ω)Context: House in Walloon Brabant, wet clay soil (ρ ≈ 100 Ω·m)Solution 1: Single 2 m earth rod (Ø 15 mm)R ≈ (100 × 2) / (2 × 3.14 × 2 × 0.0075) ≈ 84 Ω ❌ (non-compliant with RGIE)Solution: 3 x 2 m rods spaced 3 m apart → R ≈ 84 / 3 × 0.6 ≈ 16.8 Ω ✅Solution 2: 25 mm² copper loop at the bottom of the excavationHouse perimeter 10×12 m = 44 linear metresSurface area S ≈ 120 m²R ≈ (100 / (2 × 3.14 × √120)) × 0.7 ≈ 12 Ω ✅ (well within RGIE standards)⭐ Conclusion: The ground loop is 30% more efficient than a 3-pole solution, for a similar cost (≈ £200-250 for materials + labour included in the earthworks).✅ Mandatory checks and measurements🔬 Earth Resistance Measurement (62% Method)The most reliable method is the 3-stake (or 62%) measurement, carried out by the inspection body using a professional tellurometer.Disconnect the measuring strip (isolate the stake/loop installation)Drive in 2 auxiliary stakes:Voltage stake (S): 20-30 m from the main stake or loop riserCurrent stake (H): 40-50 m from the main stake or loop riserMeasurement with tellurometer (current injection + voltage measurement)Validation:🇧🇪 Belgium: R ≤ 30 Ω → RGIE compliance ✅🇫🇷 France: R ≤ 100 Ω (or ≤ 10 Ω if Type 1 surge arrester) → NF C 15-100 compliance ✅🧪 Additional checksContrôleMéthodeValeur ConformeContinuité PEMultimètre 4 fils (structure → bornier)≤ 0,5 Ω (idéal ≤ 0,1 Ω)Résistance isolement DCMégohmmètre 500-1000 V≥ 1 MΩ (isolation PV+ / PV- / PE)Déclenchement différentielTesteur différentiel calibréDéclenchement ≤ 40 ms (30 mA Type A/B)Test clips Rayvolt® (FR)Multimètre cadre → câble PE≤ 0,1 Ω par clip📞 NEED A COMPLIANT INSTALLATION?Wattuneed manages the entire installation, including VINCOTTE/Consuel inspection ⚡ REQUEST A FREE QUOTE ❓ Frequently Asked Questions (FAQ)1️⃣ Which method should I choose: stakes or a loop at the bottom of the trench?Answer:New construction: Loop at the bottom of the excavation is mandatory (2-5 times lower earth resistance, 50-year durability, cost included in earthworks)Renovation/existing: Vertical stakes (1 to 3 depending on soil) or horizontal trench if rocky soilHighly resistive soil (> 500 Ω·m): Combine loop + additional stakes to achieve ≤30 Ω (BE) / ≤100 Ω (FR)2️⃣ Are Rayvolt® clips mandatory in France?Answer: No, they are not mandatory but are strongly recommended by professional installers for:Time savings during installation (10 seconds/clip vs. 2-3 minutes/traditional clamp)No drilling of the frame → preserves the panel manufacturer's warrantyNF C 15-100 compliance certified by a notified bodySuperior long-term reliability (25-year guarantee)Compliant alternative: M6/M8 stainless steel earth claws with fan washers + crimp terminal (traditional method).3️⃣ Why does Belgium impose 30 Ω instead of 100 Ω as in France?Answer: Belgian electrical regulations prioritise maximum safety by limiting contact voltage to ≤ 50 V in all circumstances. With a 30 mA and 30 Ω differential, the residual voltage in the event of a fault is: U = 0.03 A × 30 Ω = 0.9 V (completely safe). At 100 Ω, this voltage would rise to 3 V, which is acceptable in France but considered insufficient by the Belgian FPS Economy.4️⃣ Can I reuse my home's existing earth connection for photovoltaics?Answer: Yes, it is even recommended! The PV installation must be connected to the same earth connection as the rest of the domestic installation (TT system). Simply check that the measured resistance is compliant (≤30 Ω BE / ≤100 Ω FR). If it exceeds this, add additional stakes or (if the building is recent) check that the ground loop has been properly connected to the earth terminal block.5️⃣ How much does a ground loop cost for a new house?Answer:Materials only: £150 to £250 including VAT (25 mm² bare copper cable + connectors + TPC sheathing)Labour: Often included in earthworks (installed at the same time as the foundation reinforcement)Total cost: €200 to €400 including VAT, all inclusive (vs. €150-300 for 2-3 vertical stakes)ROI: Immediate payback thanks to guaranteed compliance + superior durability (no need to replace corroded stakes after 20-30 years)6️⃣ What should I do if my soil is rocky and it is impossible to drive in posts OR dig a loop?Answer: Alternative solutions compliant with RGIE/NF C 15-100:Ground plates: 1×1 m copper/galvanised steel plates buried vertically (1 m deep trench)Multiple horizontal electrodes: 3-4 star trenches, 25 mm² bare cable over 20-30 linear metres eachGeothermal drilling (extreme solution): 10-15 m concrete-lined borehole (cost €800-1,500)Bentonite conductive gel: improves soil resistance by 30-50% around existing electrodes (≈ €80/25 kg)Contact Wattuneed for a field feasibility study with soil resistivity measurement (4-point Wenner method).Wattuneed SPRLRue Henripré 12, 4821 Andrimont, BelgiumTel: +32 87 45 00 34 – info@wattuneed.comwww.wattuneed.com | Technical support