Elevator Electrical Earthing: EN 81-20 Bonding Requirements, Earth Loop Impedance and LOLER Testing

Electrical earthing (grounding) is a fundamental safety requirement for all elevator installations. EN 81-20 mandates that all metalwork — car frame, guide rails, motor housing, control panel enclosure, hoistway metalwork, and junction boxes — must be bonded to the protective earth (PE) conductor of the supply. The earth fault loop impedance must be sufficiently low that a phase-to-earth fault causes the protective device (fuse or MCB) to operate within the time required by EN 60364-4-41 (protection against electric shock). In TN-S and TN-C-S earthing systems, the PE conductor is separate from neutral. Earth bonding conductors must be of sufficient cross-sectional area: typically a minimum of 4 mm² copper for exposed metalwork in the machine room. Guide rails can serve as the bonding conductor between the car frame and the pit, provided their cross-section is adequate. Periodic testing of earth continuity and insulation resistance is required under LOLER and IET Wiring Regulations (BS 7671 in the UK). Stray earth currents can cause accelerated corrosion of metalwork — particularly guide rails — and must be investigated if detected.

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