Lift installations — supply, bonding and RCD protection of passenger lifts

A passenger lift is an installation where the electrotechnical supply requirements (NEN 1010, based on IEC 60364) and the lift-specific safety standard (NEN-EN 81-20 for construction and installation, NEN-EN 81-50 for testing and calculation rules) apply side by side. This article covers the general supply of a passenger lift — not the separate, statutory emergency power supply for a fire-fighting lift, which is already covered in the fire-fighting lift guide.

Main switch: present, but not the only switch

Every lift installation has a lockable main switch with which the entire supply to the lift motor and control system can be switched off, for example for maintenance. A common misunderstanding is that this main switch also disconnects the lighting of the machine room and pit.

It must not. The lighting circuit of the machine room and pit must be electrically independent of the main supply to the lift drive, with its own switch. The reason is directly practical: a technician who switches off the main switch to work on the drive must not simultaneously end up in the dark in the pit or machine room — exactly at the moment manual work is being done near moving parts.

RCD protection and the influence of the variable-frequency drive

Virtually every modern passenger lift is driven by a variable-frequency drive (VFD) for soft start/stop and energy- efficient control of the lift motor. As with other VFD-fed drives (see the guide on RCD types AC/A/F/B), the rectifier/inverter stage of the VFD can cause a leakage current with a DC component in the event of an earth fault. A conventional Type A RCD cannot detect that DC component and therefore cannot reliably disconnect. A Type B RCD is therefore recommended for the supply to the lift drive — unless the VFD manufacturer's documentation demonstrates that its own topology cannot produce a DC component in the fault current.

Machine-room and pit illuminance

NEN-EN 81-20/81-50 sets minimum illuminance levels for the working spaces of a lift installation, so that maintenance and inspection can be carried out safely:

Machine room: at least 200 lux at floor level.
Pit floor: at least 50 lux, measured 1.0 m above the pit floor.

Both lighting circuits must, as described above, be separately switchable and remain functional independently of the main supply to the lift drive.

Socket outlets in the pit and machine room

For maintenance equipment (hand lamp, power tools), socket outlets are required in the pit and machine room. Like virtually every socket outlet in a technical space under NEN 1010, these fall under the general RCD requirement of §411.3.3 (see the [§531 guide on RCDs](/guides/nen-1010/531-rcd)) — residual-current protection with IΔn ≤ 30 mA.

Equipotential bonding of guide rails and shaft steelwork

The guide rails along which the lift car travels, and the structural steelwork of the lift shaft, are conductive parts that must be connected to the building's main equipotential bonding — following the same principle as for other large metal structural elements (see for example the approach used for greenhouse structures). This prevents a potential difference arising between the lift car/rails and other conductive parts in the shaft in the event of an earth fault elsewhere in the installation.

Note: the exact clause numbers in NEN-EN 81-20/81-50 fall outside the scope of this article — the standard itself is the binding source for the precise requirements per situation. This article gives the main lines of the electrotechnical supply aspects as they are also relevant in an NEN 1010 context.

Practical relevance

During commissioning or periodic inspection of a passenger lift installation (often combined with an NEN 3140 inspection of the machine room), checking the independent switching of the lighting circuits, the RCD type on the drive supply, and the equipotential bonding of guide rails and shaft steelwork is a standard part of the work — alongside the lift-specific inspections that fall under NEN-EN 81-20/81-50 and are outside the scope of the electrotechnical inspection.

Common mistakes

Putting pit/machine-room lighting on the same main switch as the lift drive — a technician can unintentionally be left without light during maintenance.
Applying a Type A RCD to a VFD-fed lift drive without manufacturer confirmation — a DC component in the fault current can render a Type A RCD blind to the fault.
Omitting guide rails and shaft steelwork from the equipotential bonding — these large metal structural elements must be included in the main equipotential bonding just like other accessible conductive parts.