Lifts for Transport of Persons and Goods
IS17900: 2022
Electrical Safety in Lifts, and the challenges
1. Introduction
This article explains the violations and nonstandard arrangements from the established Electrical safety provisions of the CEA Regulations, Codes, and Standards, jeopardising the safety of the public from electrical hazards, especially, in lift installations.
BIS published the new IS standard IS17900: Lifts for Transport of Persons and Goods. The new standards part 1 and 2 together supersedes IS 14665 (Part 1), IS 14665 (Part 2/Sec 1), IS 14665 (Part 3/Sec 1), IS 14665 (Part 4/Sec 1 to 9), IS 14671 and IS 15785.
IS17900 is based on ISO 8100, Lifts for the transport of persons and goods. Part 1 of the standard is on Safety rules for the construction and installation of passenger and goods passenger lifts.
IS17900-1 requires compliance with IS732 for protection against electric shock and thermal effects (ref clause 5.10.1.1.6, 5.10.1.2.1, 5.10.1.3, 5.10.9 & 6.3.2)
In general, the new IS17900 is going to have an impact in the construction industry.
Any violations could seriously affect the safety of passengers, reliability of the electrical and electronic devices in the lift as well as reliability of the other parts of the electrical installation in the building premises. The article also explains the reasons why noncompliance could endanger the safety of property and persons.
Note: Though several Improvements are included in IS17900 (part 1 and 2), electrical safety related points are mainly addressed in this article.
2. Mistakes in old Standards
There were few mistakes and wrong requirements in the earlier standards of lifts (IS14655 series which is superseded now), which created large scale confusion in the construction industry in India and resulted in the violation of basic electrical safety measures. The confusions is due to the following clauses in the earlier standards.
IS14665 Amendment no 1 to (part2/sec1):2000 cl. 8.4.4.7: “there shall be separate earth pit for lift”. IS 14665 (Part 5):1999 Table 4 Inspection of Lift from Machine Room. SL no 15 “The earthing arrangement shall be proper, and the electrical contractor/owner shall ensure that earth resistance shall not exceed one ohm as per Indian Electricity Rules”. |
Due to the misleading clauses in IS14665, each lift is connected to two separate earth pits. The state government departments, while implementing Lift rules insist on the compliance with IS14665. Over a period, these mistakes became an industry practice, resulting complete violation of electrical safety requirements across India, in almost all installations. Users were unnecessarily carrying out research to reduce the earth electrode resistance to less than one ohm and wrongly believe that every failure in lift installation is due to higher earth electrode resistance.
Note: This article does not consider the clauses 6.2.2 and 6.2.4 in NBC 2016. Clause 6.2.2 is not specific about fault protection or additional protection. Clause 6.2.4 is misinterpreted from IS3043 (even though it refer to IS3043). |
PART 8 BUILDING SERVICES: Section 5 Installation of Lifts, Escalators and Moving Walks: 5A Lifts 6.2.2 Residual Current Device: Residual current device (RCD), if provided, right type and sensitivity shall be selected. The RCD shall,
NOTE - This kind of RCDs are generally classified as ‘Type B’. Three-phase power supply for the lift should never be protected with a 30mA residual current device (RCD). The 30 mA RCD trips easily when the lift starts to drive and prevents the lift to run. If the construction-time power supply is for some reason protected with a 30mA residual current device (RCD), suitably sized isolation transformer needs to be provided by the electrical contractor. |
PART 8 BUILDING SERVICES: Section 5 Installation of Lifts, Escalators and Moving Walks: 5A Lifts 6.2.4 Earthing There shall be separate exclusive earth pit for the lift or a group of lifts or the same shall be connected to equipotential bonding system. There shall be two separate and distinct earth conductors provided from the earth pit to the machine room as per good practice [IS3043]. The cross-sectional area of copper earthing conductor shall be not smaller than half that of the largest current-carrying conductor subject to an upper limit of 65 mm2. In case of buildings having earthing through earth mats or earth grids, it is permissible to earth the lift equipment with separate conductors from these earth mats/grids. Separate earth pits shall not be a requirement in this case. |
3. Measures prescribed in IS3043: Code of Practice for Earthing
The following clause from IS3043: 2018 helps to understand the subject in a simple way.
Clause 23.1 Basic Purpose of Earth Fault Protection The earth fault loop impedance has to be low enough to allow adequate earth fault current to flow to cause an overcurrent protective device (for example, a fuse or circuit breaker) in the faulty circuit to operate in a sufficiently short time. or Where it is not possible to achieve a low enough earth fault loop impedance, disconnection may be initiated by fitting a residual current device (RCD) of 30 mA rating as specified in IS 732. |
Hence using RCD’s with residual operating current > 30 mA, is mandatory in case of a “failure of fault protection by OCPD” as an earth fault protective measure.
4. Measures prescribed in CEA regulations 2023
Further the following mandatory requirements of the National Electrical Safety Regulation of Central Electricity Authority (Measures Relating to Safety and Electric Supply) Regulations 2023 must be fulfilled,
Regulation 43. Connection with earth (ix) All earthing systems shall, - (b) have earth fault loop impedance sufficiently low to permit adequate fault current for the operation of protective device within the time stipulated in the relevant standards. (xi) earth fault loop impedance shall be tested to ensure the automatic operation of the protective device and a record of every earth test made and the result thereof shall be kept by the supplier for a period of not less than two years after the day of testing and shall be available to the Electrical Inspector when required. (xii) earth fault loop impedance of each circuit shall be limited to a value determined by the type and current rating of the protective device used such that, on the occurrence of an earth fault, disconnection of the supply shall occur before the prospective touch voltage reaches a harmful value. |
5. The new and modern requirements prescribed for lifts and escalators.
The following provisions are already prescribed in the standards but mostly misunderstood:
Clause 5.10.9 of IS 17900 (Part 1): 2022 recommends making protective earthing as per IS732, clause 4.2.11.3.1.1.
It should also be observed that the circuit protective device should clear the overcurrent in a disconnection time of the of less than 0.4 second as prescribed in Table 1 of IS732.
Selection of wiring system and method of Installation as per cl 5.3, 5.4, 5.5.1 to 3 and Table-2 of IS 732.
Coordination between circuit protection device, design load current, and current rating of cable (after derating as per Cl.4.6.2.3 under Section 12, Part 1 of NEC, and Cl. 4.4.5.5.2 and Table 3 of IS 732) as per Cl.4.5.1 under Section 12, Part 1 of NEC.
Compliance of non-trip conditions of the circuit protective devices for inrush current during starting as per Table 7 of IS/IEC 60898.
IS 732:2019, Clause 4.2.11.3.1.1 Protective earthing Exposed conductive parts shall be connected to a protective conductor under the specific conditions for each type of system earthing as specified in 4.2.11.4 to 4.2.11.6. Simultaneously accessible exposed conductive parts shall be connected to the same earthing system individually, in groups or collectively. Conductors for protective earthing shall comply with 5.4 and IS 3043. Each circuit shall have available a protective conductor connected to the relevant earthing terminal. Note: 4.2.11.4, 4.2.11.5 and 4.2.11.6 explains TN system, TT system and IT system respectively. |
The above non-compliance makes the installation unsafe due to improper operation or failure of the protective devices to trip during a fault.
Note: readers are also requested to understand the concept of Basic protection, fault protection and additional protection explained in IS732 to understand the subject. |
IS 17900 (Part 1): 2022 clause 5.10.1.2 Protection against electric shock, 5.10.1.2.1 General The protective measures shall comply with the provisions defined by IS 732. |
IS 17900 (Part 1): 2022 clause 5.10.1.2.3 Additional protection, Additional protection by means of a residual current protective device (RCD) with a rated residual operating current not exceeding 30 mA shall be provided for:
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6. Existing Method of Installation:
The currently followed method of connecting exposed conductive parts of lift (say lift earthing) to separate and independent earth electrodes (sometimes interconnected under soil) is a mistake and a violation of basic electrical safety requirements. This wrong method could lead to the deterioration of electrical system, serious electrical accidents and failure of electrical and electronic system and could ignite a fire.
Example of a safety issue: As a result of connecting exposed conductive parts of lift to a separate earth electrode, that part of the electrical installation becomes TT. Fault protection by OCPD & Protective equipotential bonding and automatic disconnection of supply is compromised. Hence 30 mA RCD at the lift panel becomes mandatory as recommended in IS732. Note:
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7. Example of reliability issue in the existing method:
Safety issues due to non-compliance with Regulatory provisions and standards in observing HV and LV earthing systems at the HV/LV Transformer substation .. read more. (LINK will be available soon)
8. Electrical Testing as per IS17900-1
Clause 6.3.2 of IS17900-1 recommends the following tests,
Visual check (e.g. damage, loose wires, all earth wires connected);
Continuity of the protective conductors according to 6.2.3.2 of IS 732,
Measurement of the insulation resistance of the different circuits.
Verification of the effectiveness of the measures for fault protection by automatic disconnection of supply according to 6.2.3.6 and 6.2.3.7 of IS 732.
Tests mentioned in 2 to 4 will ensure safety of lifts and protection against electric shock. Automatic disconnection by OCPD (fault loop impedance test and establishing disconnection time) is an efficient method to ensure safety.
9. Recommendation to the stakeholders for safe Lift Installation
A. LIFT MANUFACTURER
Ensure that the installation is in accordance with IS17900-1. Further information can be found in National Electrical Code of India Part 1 section 18.
Engineers are to be trained to carry out the installation as recommended in IS17900.
Educate engineers about TN/TT system and the dangers and reliability issues of making mistakes.
Ensure that the Leakage currents are less than 10 mA as recommended in the standard. Additional safety measures as per clause 5.4.3.6 of IS732 shall be implemented in case of higher leakage currents.
Provide testing instruments such as fault loop impedance and RCD testes to installation engineers and train them to carry out the tests as recommended in IS17900.
Make these tests while running in mains power and in DG.
Conduct periodic tests at least once in a year, additionally measure leakage currents as well.
Highrise buildings with own transformer and DG: Wrong system earthing is being followed in many buildings (wrong TT system with every exposed part connected to earth electrode / Neutral separately connected to earth electrode / TT system is often thought as TN-S). This is a violation of NEC and the CEA regulation. The subject need to be discussed with the builder and make a proper TN-S or TNC-S system.
Note: Violation by DISCOM in buildings with LV supply: The lift installer will face challenges due to high fault loop impedance due to noncompliance of CEA regulation 16, 17, 18 43(ii) & 74 by the DISCOM. The subject need to be discussed with DISCOM and ensure that they make the supply as TN in compliance to CEA regulations 2023. You can find more information in LINK (soon available)
B. LIFT AUTHORITY
Demanding separate earth pits for lift is a violation of CEA regulations 2023.
Ensure that the lift installer submit the test reports as mentioned in IS17900-1 during initial / periodic licensing.
C. BUILDERS
Demanding and connecting lifts to separate earth pits is WRONG. For high rise buildings make a supplementary protective equipotential bonding at the lift room. (refer part 1 section 18 of NEC 2023)
If any lift manufacturer demand as above (sl. no. 1), note that they are not technically competent to carry out this work, better to avoid using products manufactured / maintained by a non-competent company / person.
If any DISCOM / Authority demand as above (sl. no. 1), inform them that they are violating the CEA regulations, they shall be held responsible in case of accidents and failure of electronics in lifts.
10. Conclusion
IS17900 provide the correct information about safety earthing in Lift.
IS17900 provide the correct information about Verification of electrical systems used in Lifts especially earthing and safety.
The CEA safety regulations, NEC 2023, IS 732 and IS 3034 are mostly violated.
Unless the above said Regulations and Standards are complied, the hazards of equipment failure, fire and electric shock threats in the LV installations and, especially, in the lift installations will remain existing to inflict danger to the property and persons.
Prepared and published by
S. Gopa Kumar, President , National Federation of Engineers for Electrical Safety
president@nfees.org
Member in various working groups of IEC TC64, TC 81 and BIS ETD 20, ETD 30, ETD 50 & NBC 2016
S. Appavoo, General Secretary, National Federation of Engineers for Electrical Safety
secretary@nfees.org
Former Chief Electrical Inspector, Government of Tamil Nadu.
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