Initial verification, final inspection, acceptance inspection — three names, three different people

Final inspection done, safety certificate issued, installation handed over — and then the customer asks whether that was not already the acceptance inspection the grid operator keeps mentioning. The three terms sound like synonyms for the same form. They are not. The Low-Voltage Installation Ordinance (NIV, SR 734.27) distinguishes three separate inspections, with three separate people responsible, and the distinction is not a formality.

Three inspections the NIV keeps apart

The initial verification comes first and happens in-house, on site. Under Art. 24 para. 1 NIV, an initial verification accompanying construction must be carried out before an electrical installation, or parts of it, are put into service, and this initial verification must be recorded. It checks that what has just been laid or connected works and is safe, before live voltage is applied for real.

The final inspection comes before handover to the owner (Art. 24 paras. 2–6 NIV). It is carried out by a qualified person under Art. 8 NIV or by a person authorised to inspect under Art. 27 para. 1 NIV — in practice usually by whoever built the installation. That person records the results in the safety certificate (Sicherheitsnachweis) under Art. 37 NIV and hands it to the owner, who uses it to notify the grid operator that the installation work is complete.

The acceptance inspection is the only one of the three that does not come from the installer. It is based on the safety certificate together with the measurement and test report from the final inspection; it is carried out by an independent inspection body or an accredited inspection agency — expressly not by the same contractor that did the installation.

When the acceptance inspection is due at all

Not every installation gets an acceptance inspection. Art. 35 NIV distinguishes by the inspection interval that applies to the installation:

• With an inspection interval of 20 years, it is enough for the owner to show the grid operator at handover, with the safety certificate under Art. 37, that the installation complies with the regulations and has been inspected under Art. 24 (Art. 35 para. 1 NIV) — no separate acceptance inspection.
• With an inspection interval of less than 20 years — and equally for an energy generation system connected to the low-voltage distribution grid — the owner arranges an acceptance inspection by an independent inspection body or an accredited inspection agency within six months and submits the safety certificate within the same deadline (Art. 35 para. 3 NIV).
• For an energy generation system not connected to a low-voltage distribution grid, the owner submits the safety certificate to the Inspectorate when it is put into service (Art. 35 para. 2 NIV).

Which inspection interval applies to a specific property is shown by the inspection interval calculator — it also says where the annex to the NIV gives no clear answer and the inspection body decides.

Why it may not be the same person

This is where a mix-up gets expensive. Art. 31 NIV is explicit: anyone involved in planning, building, altering or repairing the installation to be inspected may not be commissioned to carry out the acceptance inspection.

The Federal Inspectorate for Heavy Current Installations ESTI names the reason outright — the four-eyes principle: two mutually independent professionals should establish the safety of the installation, not one person checking their own work. The duty applies not only to the person carrying out the final or acceptance inspection, but to all technical staff of the firm concerned — every piece of installation work and every inspection activity is attributed to the whole firm, regardless of who was personally involved.

Anyone who nevertheless carries out the acceptance inspection on their own installation commits, according to the ESTI, a punishable breach of duty within the meaning of Art. 42 let. c NIV, and a safety certificate issued in this way must be rejected by the grid operator. For a contractor, that means in practice: the acceptance inspection belongs with a different inspection body — even if someone with an inspection licence works in the firm.

What the safety certificate must contain

Art. 37 NIV lists the minimum content: the address of the installation and of the owner, a description of the installation including the standards applied, the inspection interval, the name and address of the installer, the results of the in-house final inspection — and, once one has taken place, the name and address of the inspection body and the result of the acceptance inspection or periodic inspection. It must be signed both by the people who carried out the inspection and by a person authorised to inspect.

What the final inspection actually checks — which values are measured, which insulation values and protective devices are checked — is not governed by the NIV itself but by the NIN (Low-Voltage Installation Standard); the ESTI refers to its chapter 6 for this. Which values per final circuit must appear in the report, and for which five inspections it is mandatory, is set out in the article «Measurement and test report: obligation and content».

What this means for a contractor in practice

Three things that trip people up in practice:

1. Do not lose the record of the initial verification. It is the basis on which the final inspection builds, and for installations with an Inspectorate exemption under Art. 23 NIV it is even sufficient in place of the full safety certificate.
2. With several contractors on one site, settle who is responsible for the final inspection of the installation as a whole. Art. 24 para. 2 let. b NIV provides for exactly this case — several firms, each with its own qualified supervisor, but one person whom the owner designates as responsible.
3. Do not treat the acceptance inspection as a formality. It is the inspection that genuinely puts a second, independent pair of eyes on your own work — and the only one of the three a customer will ask about if it is missing.

More on the deadline within which the safety certificate must reach the grid operator in the first place in the article «The deadline for the safety certificate has passed». Anyone looking for an independent inspection body, or acting as one, will find the background under «Inspection body or inspection agency».

The most common case at the moment is a charging station: it is an electrical installation like any other and goes through the same inspections. What else has to be settled when installing a wallbox — who decides in a community of owners, and what must be reported to the grid operator — is set out in the article «Wallbox in condominium ownership».

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Sources: Federal Inspectorate for Heavy Current Installations ESTI, Daniel Otti, «Schlusskontrolle und Abnahmekontrolle», bulletin.ch 3/2017. Low-Voltage Installation Ordinance (NIV, SR 734.27), Art. 24, 31, 35 and 37, version of 1 July 2021 / 1 January 2022, fedlex.admin.ch. This article is not legal advice; in case of doubt, the responsible grid operator or the ESTI decides.