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IS 14772:1999 is the Indian Standard (BIS) for single-phase and three-phase distribution boards. This standard specifies the requirements for factory-built, single-phase and three-phase distribution boards for voltages up to 415V AC and currents up to 250A. It covers construction, safety, performance characteristics, and testing procedures for DBs intended for use in residential, commercial, and industrial electrical installations.
Specifies requirements for factory-built assemblies of switchgear and control gear, commonly known as distribution boards, for use in domestic and commercial electrical installations.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! CRITICAL: This standard has been superseded by IS 8623 (Part 3):2017. All new specifications must refer to the latest standard, although IS 14772 is relevant for existing installations.
! When specifying or inspecting DBs, verify the sheet metal thickness as per Clause 5.1.2, as this is a common point of non-compliance affecting rigidity and safety.
! Ensure the specified IP rating (e.g., IP2X for indoor, IP54 for outdoor) is appropriate for the installation environment to prevent ingress of foreign objects and water.
Low-voltage switchgear and controlgear assemblies - Part 3: Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access for their use - Distribution boards
IS 14772:1999 was largely based on this withdrawn standard, sharing its core principles and test methodologies.
Key Differences
≠IS 14772 is based on the older 'Type Test' (TTA) concept from IEC 60439, whereas modern standards like IEC 61439-3 use a more rigorous and comprehensive 'Design Verification' process.
≠IEC 61439-3 places single-point responsibility on the 'assembly manufacturer' for the final product, while the TTA/PTTA approach implied by IS 14772 could lead to divided responsibility between the enclosure manufacturer and the panel builder.
≠IS 14772 specifies a prescriptive minimum sheet steel thickness (e.g., 1.2 mm), while IEC 61439-3 uses a performance-based approach requiring the assembly to pass specific mechanical impact (IK code) and corrosion tests, regardless of thickness.
≠The international standards have more detailed requirements for temperature rise verification, including the application of a Rated Diversity Factor (RDF) to simulate realistic loading conditions, a concept not explicitly defined in IS 14772.
Key Similarities
≈Both standards cover the design, construction, and testing of low-voltage distribution boards intended for fixed installations in residential, commercial, and light industrial environments.
≈Core safety verification tests are conceptually similar, including dielectric strength (high voltage) tests, verification of clearances and creepage distances, and checking the continuity of the protective circuit (earthing).
≈Both standards specify fundamental constructional requirements for the enclosure, including provisions for cable entry, mounting of components, and an earthing terminal.
≈The rated operational voltage ranges are similar, covering single-phase systems up to 240V and three-phase systems up to 415V.
Parameter Comparison
Parameter
IS Value
International
Source
Maximum Rated Current of Board (InA)
Up to 100 A
Up to 250 A
IEC 61439-3:2012
Enclosure Material Thickness (Sheet Steel)
Prescriptive: Not less than 1.2 mm
Performance-based: Must pass specified mechanical impact (IK) and corrosion tests
IEC 61439-1:2011
Temperature Rise Limit for Terminals
50°C rise over ambient
70 K (70°C) rise over ambient
IEC 61439-1:2011
Dielectric Test Voltage (for 415V System)
2.5 kV AC for 1 minute
Typically 2.0 kV AC for 1 minute (for a Rated Insulation Voltage of 500V)
IEC 61439-1:2011
Minimum Degree of Protection (Indoor)
IP20
IP2XC when door is open; IP30 when door is closed
IEC 61439-3:2012
Short-Circuit Test Requirement
Type test for short-time withstand current (Icw) for 1 second is specified.
For DBOs, Icw test is not mandatory if the conditional short-circuit rating (Icc) with a specified protective device is verified.
IEC 61439-3:2012
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Rated operational voltageup to and including 415 V AC
Rated currentnot exceeding 250 A
Minimum sheet steel thickness (side > 500mm)1.6 mm
Minimum sheet steel thickness (side <= 500mm)1.2 mm
Minimum degree of protection for indoor boardsIP2X
Minimum degree of protection for outdoor boardsIP54
Maximum temperature rise for terminals50 °C above ambient
Tables & Referenced Sections
Key Tables
Table 1 - Clearances and Creepage Distances
Table 2 - Verification of Degree of Protection
Table 3 - Cross-sectional Area of Copper Conductors