Fire-fighting lifts and safety services — electrical supply per IEC 60364-5-56 and NEN-EN 81-72

The guide on function-retaining cable briefly mentions a fire-fighting lift or pressurisation system as an example of a system that must keep functioning during a fire, and covers the cable itself (E/PH classes) in that context. This article covers a different, prior aspect: the supply architecture of such a circuit — what IEC 60364-5-56 ("safety services") prescribes for this, and the additional, lift-specific requirements of NEN-EN 81-72.

What sets a safety service apart from ordinary standby power

The guide on ATS transfer switches and the guide on standby generators (§551) cover standby power in the sense of operational continuity: an installation that keeps functioning when the public grid fails. A safety service in the sense of IEC 60364-5-56 is fundamentally stricter: it concerns a circuit that must specifically keep functioning during a fire itself — a fire-fighting lift, a stairwell pressurisation system, a sprinkler pump, a fire alarm system. Where ordinary standby power bridges a grid outage, a safety service must hold up while the installation itself is potentially being damaged by fire.

Why RCD/AFDD protection can be counterproductive here

For an ordinary circuit, automatic disconnection of supply on a fault (for example via an RCD) is a core principle of electrical safety. For a safety-service circuit that is different: a fire itself often causes insulation faults (burnt wiring, melted insulation) — exactly the moment the circuit must keep working. An RCD or arc-fault detection device (AFDD) that disconnects on such a fault then denies the fire brigade exactly the tool (the lift, the pressurisation system) the circuit was intended for.

For this reason, IEC 60364-5-56 explicitly provides that safety-service circuits should not be protected by an RCD or AFDD where that protection would undermine reliability under fire conditions. Where non-disconnection on a first fault is required, an IT system with insulation monitoring (IMD) is generally preferred, giving an audible/visible alarm on a first fault without interrupting the supply — the same principle covered in the guide on the IT system, applied here to a safety-service circuit rather than to operational continuity in general.

Note: this does not mean no shock protection measure applies at all — other measures (double insulation, physical separation, careful cable routing) still apply. The point is specifically that automatic disconnection on a fault, as a shock protection measure, is deliberately reconsidered for this type of circuit where that disconnection would endanger operation during a fire — consult the full standard for the exact conditions of application.

Two independent power sources (NEN-EN 81-72)

In addition to the general safety-service requirements of IEC 60364-5-56, NEN-EN 81-72 (fire-fighting lifts) sets an additional, lift-specific requirement: the supply to the fire-fighting lift may not be combined with the supply to other, non-safety-critical loads, and must be able to maintain its function for a sufficient duration during a fire — in practice usually realised with two independent power sources and an automatic changeover between them, so that a fault or fire damage to one source does not put the lift out of service. See the guide on ATS transfer switches for the general operation of such an automatic changeover.

Cable routing: function retention and physical separation

The supply cable to a fire-fighting lift must itself have function retention (see the guide on function-retaining cable for the E/PH classes per NEN 6069/IEC 60331/EN 50200) — but function retention of the cable itself is not sufficient if that cable shares a route with other, non-function-retaining wiring within the same fire compartment: a fire affecting that compartment could damage the surroundings of the function-retaining cable enough (for example failing fixing hardware) that the cable still fails, even though the cable itself meets the test standard. A careful design therefore accounts for both the cable classification itself and its physical routing relative to other circuits.

Practical relevance

When designing or assessing the electrical supply of a fire-fighting lift or comparable safety service (sprinkler pump, pressurisation system), it should be verified: (1) whether RCD/AFDD protection on the safety-service circuit itself does not undermine reliability during fire, (2) whether, where non-disconnection on a first fault is required, an appropriate system (generally IT with IMD) has been applied, (3) whether two independent power sources with automatic changeover are present, and (4) whether the supply cable both has function retention itself and is physically separated from non-critical wiring.

Common mistakes

Assuming an RCD always improves safety, even on a safety-service circuit, without consulting IEC 60364-5-56 on when that assumption does not hold.
Routing the fire-fighting lift's supply cable along the same path as ordinary, non-function-retaining wiring within the same fire compartment — the cable's own function-retention classification does not compensate for this.
Using only a single power source without the second, independent source with automatic changeover intended by NEN-EN 81-72.
Confusing this continuity requirement with ordinary operational- continuity standby power (such as for a grid outage), thereby applying weaker requirements than a during-fire-functioning circuit requires.