Energy class ES1/ES2/ES3 under IEC 62368-1 — hazard-based safety for ICT and AV equipment

The guide on protection class I, II and III (IEC 61140) covers how an installation or device protects against an electrical hazard through earthing, double insulation, or SELV/PELV. This article covers a somewhat different, newer approach that applies specifically to information-technology and audio/video equipment: the hazard-based safety engineering method of IEC 62368-1.

From prescriptive rules to an energy-source model

From the 2020s onward, IEC 62368-1 replaced both IEC 60950-1 (IT equipment) and IEC 60065 (audio, video and similar equipment) — two older standards that largely relied on fixed, prescriptive construction requirements. IEC 62368-1 instead works with a generic three-block model: an energy source (electrical, thermal, mechanical, radiated, chemical or kinetic energy) is separated from a body (a person, combustible material, or another device) by a transfer mechanism through one or more safeguards. This makes the standard technology-neutral: new device forms don't have to wait for a specific, updated list of requirements, as long as the energy sources are correctly classified and provided with sufficient safeguards.

The three energy classes: ES1, ES2, ES3

For each type of energy source (this article focuses on the electrical variant), IEC 62368-1 defines three classes, based on what happens to a human being on contact:

ES1: the energy source is not perceptible or painful on contact, both under normal operating conditions and under a single fault condition — comparable to SELV-like voltage levels.
ES2: the energy source can be painful on contact but does not cause injury, at least as long as exposure remains brief — a level at which a person reflexively withdraws without lasting harm.
ES3: the energy source can actually cause injury, both under normal conditions and under a single fault condition — comparable to a regular mains-voltage circuit.

Note: the exact voltage, current and power limits between ES1/ES2/ES3 are table values in IEC 62368-1 (depending on, among other things, AC/DC, frequency and waveform) — as a rough indication, the ES1/ES2 boundary lies in the order of a few tens of volts AC and the ES2/ES3 boundary in the order of a hundred-and- some volts AC; for a concrete assessment the tables in the standard itself apply, not a rule of thumb.

Three categories of persons, not one

Just as important as the energy class is who can come into contact with the energy source. IEC 62368-1 distinguishes:

Ordinary person (OP): a layperson without training, such as an end user at home or in an office.
Instructed person (IP): someone with basic instruction and some awareness of the hazard, for example maintenance staff working to a procedure.
Skilled person (SP): a competent person who can recognise and avoid the hazard, comparable to the IV/VP roles in the guide on IV, WV, VP, VOP and layperson.

The same ES2 energy source that requires two independent safeguards for an ordinary person may be accessible to a skilled person behind just one safeguard (or sometimes even none, provided that person acts consciously and deliberately) — the standard therefore ties the required protection level to the combination of energy class and person category, not to the energy class alone.

Basic, supplementary and reinforced safeguards

A safeguard is any means that separates an energy source from a body: an enclosure, an insulation layer, a distance, a current- limiting resistor, a fuse. IEC 62368-1 distinguishes:

Basic safeguard: prevents contact under normal operating conditions.
Supplementary safeguard: a second, independent safeguard that maintains protection if the basic safeguard fails.
Reinforced safeguard: a single safeguard that provides a protection level equivalent to a basic plus a supplementary safeguard together — comparable to the concept of "reinforced insulation" in protection class II.

For an ES2 or ES3 energy source accessible to an ordinary person, two independent safeguards are typically required (basic + supplementary, or one reinforced safeguard) — the same underlying principle of "a single failure must not lead to hazard" that recurs in other safety standards too.

Practical relevance

For anyone assessing ICT or AV equipment as part of a NEN 3140 programme — think of a server cabinet, a network power supply, or an AV installation in a meeting room — it is useful to know that the CE certification of such equipment is now most likely tested against IEC 62368-1 rather than the older IEC 60950-1/60065. When in doubt about the safety of a modified or self-built power circuit inside such equipment (for example a non-factory power connection), the question "what energy class does this circuit have, and is there one reinforced or two independent safeguards between this circuit and an ordinary person?" is a useful framework, even outside a formal laboratory test.

Common mistakes

Confusing IEC 62368-1 with a purely electrotechnical standard — the energy classes and safeguard model apply equally to thermal, mechanical and chemical energy sources (for example a hot surface or a moving part inside a device).
Assuming "ES2" is always safe enough for any user — the required number and type of safeguards depends on the person category; what is acceptable for a skilled person may be insufficiently protected for an ordinary person.
Treating a single safeguard as sufficient for an ES2/ES3 source accessible to an ordinary person, without checking whether it is a basic, supplementary or reinforced safeguard.
Assuming an old IEC 60950-1 or IEC 60065 certificate is still valid for newly placed-on-the-market equipment — both standards have been withdrawn for most application areas in favour of IEC 62368-1.