What is NEN 3140 about?
NEN 3140 covers the safe operation of low-voltage electrical installations and equipment. It is the Dutch supplement to NEN-EN 50110. Besides safe working, it describes the periodic inspection: checking whether an installation or a piece of equipment is still safe.
The Dutch Working Conditions Decree (Arbobesluit) requires employers to keep electrical installations and equipment safe. An inspection under NEN 3140 is the usual way to show that.
How often?
The interval follows from a risk assessment: how heavily an installation is used, in what environment and what the previous inspection found. For installations, once every five years is a common starting point. Equipment such as extension cords and hand tools is often checked every year or more often.
The NEN 3140 protocol in Servaro uses these default intervals. If your risk assessment says otherwise, you adjust the maintenance plan.
| Check | Default interval |
|---|---|
| Periodic inspection | Every 60 months |
| Annual check | Every 12 months |
How does an inspection go?
- Preparation: agree on the scope, have the previous report and current drawings at hand and make the installation safe to work on.
- Visual inspection: are distribution boards closed and labelled, is there no damage or heat build-up, are cables protected and is the main switch within reach.
- Measurements and tests: including the insulation resistance, the earth loop impedance, the earth electrode resistance and the operation of the residual current devices.
- Equipment: check cords and plugs, label approved equipment and set rejected equipment aside.
- Result: discuss the findings with the customer.
What goes in the report?
An inspection report shows what was done and what was found. In practice it contains:
- the scope: which installations, distribution boards and equipment were inspected, and which were not;
- the measurements, with the measured values and the measuring equipment used;
- the defects, with how serious they are and the period within which they must be repaired;
- who did the inspection, and when.
Defects must be repaired. Record the repair as well, so you can show the installation is in order again.
And SCIOS?
SCIOS is a certification scheme for the inspection and maintenance of technical installations. A SCIOS inspection is carried out by an inspection company certified for that scheme. The scheme is divided into scopes, each for its own type of inspection, such as inspecting electrical installations for fire risk. Insurers often ask for such an inspection.
A NEN 3140 inspection and a SCIOS inspection overlap, but they are not the same. NEN 3140 is mainly about safe working and safe use; a SCIOS inspection is often about the risk to the building and the insurance. Which one you need depends on what the employer, the insurer or the client asks for.
This article is a practical summary, not a substitute for the standard or the certification scheme. Servaro records your own inspections; it is not an inspection body and certifies nothing.