Earthing, also known as grounding, is a fundamental aspect of electrical safety in Elevator and Escalator systems. It involves connecting electrical equipment and components to the earth to ensure any fault currents are safely dissipated. Proper earthing is vital for protecting users from electric shocks, preventing equipment damage, and ensuring compliance with safety standards.
Why Earthing is Essential
In Elevator and Escalator systems, numerous electrical components operate continuously. Without effective earthing, fault currents caused by insulation failures or short circuits can create dangerous voltage levels on metallic parts, posing severe risks to users and maintenance personnel. Proper earthing provides a low-resistance path for these fault currents, facilitating the prompt activation of protective devices like circuit breakers, thereby enhancing overall system safety.
Key Areas Requiring Earthing
All metal parts of the lift may become live due to insulation failure are subject to grounding.
This includes:
- The enclosures of all electrical appliances
- The guide rails
- Lift cabin
- Controller cabinet back plate, socket outlet and controller cover / door
- Car top socket outlet
- Housing of inspection panel at car top
- Car front door / primary panel and rear door / secondary panel
- Housing of frequent converter
- Housing of machine
- Housing of brake
- Car or Counterweight Overspeed Governor
- Housing of emergency STOP switches
- Each landing door and Landing door lock contact plate
- Hoistway lights and Hoistway sockets
- Pit socket outlet and Pit metal equipments
Consequences of Inadequate Earthing
Poor or absent earthing can lead to severe consequences, including:
- Electrical Shocks: Users and maintenance personal are at risk of electric shocks, which can be fatal.
- Equipment Damage: Electrical faults can cause significant damage to elevator and escalator components, leading to costly repairs and operational downtime.
- Fire Hazards: Fault currents not properly earthed can generate excessive heat, increasing the risk of fire.
Real-Life incidents underscore these dangers. For instance, during Covid in May 2020, Two individuals in Rajkot were electrocuted while operating an elevator in a residential building. (Click here to read full article). Similarly, in Ahmedabad, A young girl tragically lost her life due to an electrical shock from an elevator. (Click here to read full article).
Standards and Regulations for Earthing
Adhering to established standards is crucial for ensuring the safety and reliability of elevator and escalator systems. The specific earthing requirements are:
- Separate Earth Pit: As per NBC, There shall be separate exclusive earth pit for the lift or a group of lifts, or they shall be connected to an equipotential bonding system.
- Dual Earth Conductors: As per NBC, Two separate and distinct earth conductors should be provided from the earth pit to the machine room.
- Conductor Sizing: Shall match any one criteria:
- The insulated protective conductor cross section is ≥ 100 square millimeters.
- If the insulated protective conductor of the mains supply has a cross section of < 10 square millimeters: A second insulated protective conductor with at least the same cross section is connected.
- The bare protective conductor of the mains supply has a rectangular cross section of ≥ 24 square millimeters and is made of Copper (Cu) or Aluminium (Al).
- If the bare protective conductor of the mains supply has a cross section of < 24 square millimeters: A second bare protective conductor with at least the same cross section is connected. The bare protective conductors is made of copper (Cu) or Aluminium (Al).
- The guide rails are connected to the equipotential bonding.
- As per National Building Code (NBC), The cross-sectional area of the copper earthing conductor shall be not smaller than half that of the largest current-carrying conductor subject to an upper limit of 65 square millimeters.
- Earthing Terminals: The terminal for earthing the frame of the motor, winding machine, control panel, and similar electrical appliances should be at least equivalent to a 10mm diameter bolt, stud or screw. For metallic cases and covers of door interlocks, door contacts, call and control buttons, STOP buttons, car switches, limit switches, junction boxes, and similar fittings, the terminal should be at least equivalent to a 5mm brass screw, with the earth conductor size being at least 0.5 square millimeter copper.
Additionally, as per IS17900 Part1, clause 5.10.1.2.3, Residual Current Devices (RCDs) with a rated residual operating current not exceeding 30mA are required for:
- Socket Outlets and Lighting Circuits: Including switches for car lighting circuits and dependent circuits, hoistway lighting and dependent circuits.
- Control Circuits: For landing controls and indicators, and the safety chain with voltage higher than 50VAC.
- Lift Car Circuits: With voltage higher than 50VAC.
Proper earthing in elevator and escalator systems is not just a regulatory requirement but a critical safety measure. It ensures the protection of users and equipment, prevents potential hazards, and complies with national standards. Building owners and maintenance personnel must prioritize effective earthing practices to safeguard lives and property.
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