SELV, PELV & FELV — the extra-low-voltage measure
§414 — SELV, PELV & FELV — the extra-low-voltage measure
SELV, PELV and FELV are three variants of extra-low voltage, but only two of them count as a full protective measure against electric shock. §414 treats this as a general principle, independent of a specific space — the bathroom guide (§701) applies this principle only within the context of wet locations; §414 itself applies everywhere extra-low-voltage circuits are used (garden lighting, playground equipment, control circuits of machines, and so on).
The limit values
| Dry/normal conditions | Damp/wet conditions | |
|---|---|---|
| SELV / PELV | ≤ 50 V AC / ≤ 120 V DC | ≤ 25 V AC / ≤ 60 V DC |
Below these values, no additional protection against direct contact is generally required; below 25 V AC in dry conditions, the need for basic protection even disappears in many practical situations (depending on surface contact and environment).
SELV versus PELV versus FELV
| Separation from the mains | Earthing | Full protective measure? | |
|---|---|---|---|
| SELV (Safety Extra-Low Voltage) | Full galvanic separation via safety transformer | Not earthed | Yes |
| PELV (Protective ELV) | Full galvanic separation | May be earthed at one point | Yes |
| FELV (Functional ELV) | No full safety separation — functional reason for low voltage (e.g. operating comfort), not safety separation | Variable | No |
The crucial difference: SELV/PELV require a safety transformer (or equivalent separation) that fully separates the extra-low-voltage circuit from higher voltages. A FELV circuit can have an extra-low voltage without this separation — for example, a transformer that steps down voltage purely for functional purposes, not for safety separation. Such a circuit may not be regarded as the sole protective measure: additional basic protection is required, as if it were an ordinary low-voltage circuit.
Practical applications
- Garden and outdoor lighting: often implemented as SELV (12V/24V) to limit the risk of contact during digging work or with damaged cables. NEN 1010:2020 §715.414.1 even prescribes exclusively SELV for extra-low-voltage lighting — PELV is not sufficient here.
- Machine control circuits: often FELV — functionally low voltage (e.g. 24V DC PLC control), but without safety separation, so the panel still requires full basic protection.
- Play equipment and swimming pool lighting: SELV with the stricter 25V/60V limit due to the damp/wet environment.
Common mistakes
- Regarding every low voltage as "safe" — a FELV circuit can have the same voltage as SELV but lacks the safety separation; it does not protect in the same way.
- Applying PELV where §715.414.1 requires SELV — for extra-low-voltage lighting, PELV (with its earthing point) is not permitted as a substitute for SELV.
- Applying the dry-conditions limit (50V/120V) in wet locations — the stricter 25V/60V limit applies as soon as the environment is damp/wet (compare the bathroom zones in §701).
- Assuming that a galvanically separated transformer automatically produces SELV — if the secondary circuit is earthed at even a single point, it is by definition PELV, not SELV; this distinction is relevant for which applications are permitted (see §715.414.1 above).