NIBT 2020 — Swiss Low-Voltage Installations Standard
Electrosuisse technical reference SEV 1000:2020, aligned with IEC 60364. All key chapters, safety principles and differences with the European standards.
What is the NIBT?
The NIBT (Low-Voltage Installations Standard), also called SEV 1000:2020, is the technical reference standard for any low-voltage electrical installation carried out in Switzerland. It is published and maintained by Electrosuisse (Association for electrical engineering, energy and information technologies), which is its official authority for the Confederation.
NIBT 2020 aligns very closely with the international series IEC 60364 (« Low-voltage electrical installations ») and its European equivalent HD 60364. It does, however, add requirements specific to Swiss conditions: earthing system, cable cross-sections per Swiss and German-speaking practice, inspection intervals, bilingual French/German terminology.
It is essential to distinguish the NIBT from theOIBT (Ordinance on Low-Voltage Installations). The OIBT is the federal legal which makes compliance with the technical rules mandatory: it defines who may install, who inspects, what the deadlines are and which documents must be handed over to the distribution operator. The NIBT is the content technical which the OIBT makes legally binding. In practice, Art. 3 and Art. 4 of the OIBT refer to the NIBT for the material conformity of the installation.
Internationally, NIBT 2020 must be distinguished from two neighbouring standards that are very often confused:
- NF C 15-100 (France): derived from the same IEC 60364 but with specific French requirements (bathroom zones, number of socket outlets per room, AGCP, GTL). Is not applicable in Switzerland.
- VDE 0100 (Germany): also derived from IEC 60364, similar requirements but different earthing system and terminology.
In a Swiss execution file, NIBT 2020 is cited for design (cross-sections, protective devices, selectivity), for implementation (installation, labelling) and for verification (measurements and test reports kept at least until the next inspection).
Structure of NIBT 2020
NIBT 2020 adopts the six-part structure of IEC 60364. Each part is itself divided into chapters and sub-chapters numbered on three or four levels. This numbering is universal: a reference "NIBT 4.1.3" points to the same place as IEC 60364-4-41.
- Part 1 — Scope, object and fundamental principles (chapter 1). Defines what the standard covers (up to 1000 V AC and 1500 V DC), the exclusions (public distribution networks, very-high-voltage railway traction, lightning) and the main safety principles: protection of persons, protection of property, reliability of service.
- Part 2 — Definitions (chapter 2). Unified technical vocabulary: “final circuit”, “direct contact”, “indirect contact”, “fault current”, “disconnection time”. Essential for a consistent reading of chapters 4 to 6.
- Part 3 — General characteristics of installations (chapter 3). External influence conditions (humidity, temperature, presence of water classified AD, accessibility BA), classification of installations, and above all the choice of the earthing system (TT, TN-S, TN-C, TN-C-S, IT).
- Part 4 — Protection for safety (chapter 4). Protection against electric shock (4.1), protection against thermal effects (4.2), protection against overcurrent (4.3), protection against voltage disturbances (4.4), isolation and switching (4.6). This is the designer's day-to-day normative core.
- Part 5 — Selection and erection of equipment (chapter 5). Common rules (5.1), wiring systems and cables (5.2), protective switchgear (5.3), earthing and protective conductors (5.4), other equipment (5.5), safety services (5.6). Includes minimum cross-sections and installation methods.
- Part 6 — Verification (chapter 6). Initial verification (6.1), measurements to perform (PE continuity, insulation resistance, loop impedance, RCD tripping, earth), and above all the periodic verification (6.4) with its deadlines.
Beyond the six parts, NIBT 2020 adds chapters 7XX (special rooms and applications: bathrooms 701, swimming pools 702, saunas 703, construction sites 704, agricultural premises 705, heated floors 753, photovoltaics 712, EV charging points 722, medical locations 710) and Swiss national annexes (NB) indicated in the text by a grey box.
Key chapters and rules
| Chapter | Subject | Typical application |
|---|---|---|
| 3.1 | Supply characteristics | Nominal voltages 230/400 V, frequency 50 Hz |
| 3.1.2 | Earthing systems | TT in residential, TN-S in industry, IT in medical |
| 3.1.3 | Supply cross-sections | Determining the supply conductor |
| 4.1.3 | Automatic disconnection of supply | Disconnection time ≤ 0.4 s for circuits ≤ 32 A |
| 4.1.5 | Extra-low voltage SELV / PELV | Doorbells, pool lighting, 12-24 V signalling |
| 4.1.7 | Additional protection with 30 mA RCD | Socket outlets ≤ 32 A, wet rooms, outdoor areas |
| 4.3 | Overcurrent protection | Circuit breakers, fuses, selectivity |
| 4.4 | Protection against transient overvoltages | SPD surge arresters type 1 / 2 / 3 |
| 5.2.4 | Current-carrying capacities of cables | Tables A to G by installation method |
| 5.2.5 | Voltage drop | 3 % lighting, 5 % power |
| 5.3.7 | Residual current devices (RCDs) | Type A standard, type B for PV and EV |
| 5.4 | Earthing and equipotential bonding | Foundation earth electrode, main equipotential bonding |
| 6.1 | Initial verification by measurements | Report to submit with the OIBT installation notification |
| 6.4 | Periodic verification | Inspection interval 1 / 5 / 10 / 20 years depending on use |
| 7.10 | Medical locations | Groups 0/1/2, IT earthing system, isolation transformer |
TT earthing system mandatory in Switzerland
The structuring rule most often overlooked by designers coming from France or Germany is the earthing system. NIBT 2020, in continuity with NIBT 2000, imposes the system TT (transformer neutral earthed, exposed conductive parts of the loads connected to an independent earth) for installations supplied directly by the public low-voltage network of most Swiss utilities (Romande Energie, SIG, Groupe E, Services Industriels de Lausanne, ewz, BKW depending on the area).
The systems TN-S and TN-C-S are only permitted in specific cases:
- Industry with a private transformer substation (own HV/LV substation), where the operator chooses the earthing system.
- Swiss Federal Railways and railway infrastructure supplied by their own network.
- Large commercial sites with a private transformer and the utility's approval.
The system IT (isolated or impedance-earthed neutral) is strictly reserved for group 2 medical locations (chapter 7.10), to certain critical computer rooms and to specific industrial installations where continuity of service takes precedence over disconnection at the first fault.
This peculiarity is the opposite of Germany, where the TN-C-S est dominant en habitat (le neutre et le PE sont confondus depuis le poste HTA/BT jusqu'au tableau divisionnaire), et différente de la France, où le TT est aussi la règle mais où les protections différentielles tête de tableau sont calibrées sur des valeurs et des prises de terre maximales différentes (100 Ω en France contre des exigences NIBT exprimées en boucle de défaut). Un projeteur qui copie un schéma allemand sans adapter la prise de terre et la sélectivité différentielle produit un dossier non conforme NIBT 2020.
Inspection intervals
Chapter 6.4 of NIBT 2020 sets the periodic verification intervals. These intervals are adopted and made binding by the annex to the OIBT (inspection schedule). The designer must take them into account from the design stage: the accessibility of the panel, the labelling of the circuits and the quality of the documentation determine the future cost of each inspection.
- Residential (dwellings, apartment buildings) — inspection every 20 years, extended to common areas.
- Shops, offices, craft workshops — every 10 years.
- Schools, nurseries and other facilities for children — every 10 years, with particular attention to practical-work rooms and science laboratories.
- Hotels, restaurants, public halls — every 5 years.
- Industry, permanent construction sites, agriculture — every 5 years.
- Service stations, ATEX explosion-risk areas — every 3 years.
- Group 2 medical locations (operating theatres, ICUs), public saunas, public swimming pools — every 1 to 3 years according to classification.
Minimum cable cross-sections
Chapter 5.2 defines the minimum cross-sections according to the circuit's function. The values below are the NIBT 2020 minimums for copper, PVC insulation, installation in conduit or standard surface mounting. Any increase for voltage drop (chapter 5.2.5) or cable grouping must be added to these minimums.
- Lighting circuits — 1.5 mm² copper, 10 A protection.
- Standard socket circuits — 2.5 mm² copper, 13 or 16 A protection depending on the RCD.
- Cooking (cooker, oven) — 4 mm² copper minimum, 20-25 A protection.
- Dedicated washing machine, dishwasher, tumble dryer — 2.5 mm², dedicated circuit with 30 mA RCD.
- Water heater, boiler — 2.5 mm² up to 3.5 kW, otherwise 4 mm².
- Heat pump — 6 mm² for single-phase heat pumps, 10 mm² three-phase above 7 kW.
- Electric vehicle (EV) charging station — 6 mm² for an 11 kW wallbox (16 A three-phase), 10 mm² for 22 kW (32 A three-phase).
- Main supply of a single-family-home distribution board — minimum 10 mm² depending on distance and subscribed power.
These cross-sections should be cross-checked against the voltage drop of chapter 5.2.5: 3 % maximum between the origin and the point of use for lighting circuits, 5 % for motor power circuits and other uses. Over long distances (outbuilding on a farm plot, chalet annex) it is the voltage drop that governs the sizing, not the current-carrying capacity.
Mandatory RCDs
Residual current protection is governed by chapters 4.1.7 (additional protection) and 5.3.7 (RCD selection). The minimum Swiss rules in NIBT 2020 are:
- 30 mA mandatory on all circuits of socket outlets ≤ 32 A, on all circuits of wet rooms (chapter 701), on the outdoor circuits, on the construction sites (704) and on the residential lighting circuits since the 2020 revision.
- 300 mA or 500 mA in panel incomer or on the main outgoing feeders for protection against fires of electrical origin (selective, time-delayed « S »-type RCDs).
- Type A by default: detects AC faults and pulsating currents with a DC component (chargers, household power electronics).
- Type B mandatory as soon as there is smooth direct current : photovoltaic installations with an inverter without galvanic isolation, EV charging stations (unless the wallbox already includes 6 mA DC detection), variable frequency drives industrial.
- Type F recommended for circuits supplying variable-frequency appliances (inverter heat pumps, modern household appliances).
The selectivity between the upstream RCD (300 mA selective, type S) and the downstream RCDs (30 mA instantaneous) is required to avoid a general trip on a local fault. This selectivity must be verified both on the current threshold and on the non-tripping time.
FAQ — NIBT 2020
Is NIBT 2020 mandatory? Indirectly, yes. The NIBT itself is a private technical standard published by Electrosuisse. It is theOIBT (federal law text, RS 734.27) which makes compliance with it mandatory: art. 3 OIBT requires installations to be “in accordance with the recognized technical rules”, and the NIBT is the concrete implementation accepted by the Confederation and all utilities.
What is the difference between the NIBT and IEC 60364? NIBT 2020 adopts the six-part architecture and almost all of the content of IEC 60364, but adds Swiss requirements (TT earthing system by default, inspection intervals, bilingual FR/DE terminology, references to the OIBT and to SIA 451 for documentation). In short: IEC 60364 = the international skeleton, NIBT 2020 = the same standard dressed the Swiss way.
Where to download the NIBT 2020? It cannot be downloaded free of charge. The official text is sold by Electrosuisse in printed form or as online subscription access (NIBT Online). Engineering offices and licensed installers are required to have it. Beware of PDFs circulating on the internet: often NIBT 2010 or 2015, hence outdated on the RCD, EV and PV chapters.
How often does the NIBT change? Historiquement, environ tous les cinq ans : NIBT 2000, NIBT 2005, NIBT 2010, NIBT 2015, NIBT 2020. Des correctifs intermédiaires sont publiés par Electrosuisse (errata, fiches d'interprétation). La prochaine édition majeure est attendue dans la continuité du cycle quinquennal et intégrera les évolutions IEC 60364 sur la mobilité électrique, le stockage d'énergie résidentiel et la protection contre les arcs (AFDD).
Does the NIBT apply to photovoltaic installations? Yes, entirely, via the chapter 7.12 (photovoltaic power supplies). The requirements cover DC wiring, earthing, the rooftop DC disconnector, string protection, arc detection, the type B RCD on the AC side, safety labelling for firefighters and coordination with the general NIBT. The specifics of a connection to the public grid additionally fall under the utility's requirements and the SN EN 50438.
What is the difference with NF C 15-100 and VDE 0100? Les trois normes dérivent d'IEC 60364 et se ressemblent à 80 %. Les différences : la NF C 15-100 impose un nombre minimum de prises par pièce et des volumes de salle de bain spécifiques (V0, V1, V2) absents de la NIBT. La VDE 0100 favorise le régime TN-C-S et utilise des sections imposées par DIN VDE 0298. La NIBT 2020 garde TT par défaut, intègre des règles SIA (380/4 éclairage, 451 documentation) et renvoie à l'OIBT pour la dimension légale.
Resources
- Electrosuisse — official publisher of NIBT 2020
- ESTI — Federal Inspectorate for Heavy Current Installations
- OIBT — SR 734.27 — federal legal basis