IS 732:1989 is the Indian Standard (BIS) for electrical wiring installations. IS 732 is the fundamental code of practice for electrical wiring installations in buildings. It provides essential guidelines for the design, selection of equipment, erection, and testing of electrical wiring systems to ensure safety from fire and electric shock.
Provides general requirements for electrical wiring installations in buildings, covering design, selection of equipment, erection, inspection, and testing.
Key limits for circuit design, installation clearances, conductor identification, and testing criteria for electrical wiring installations.
| Reference | Value | Clause |
|---|---|---|
| Voltage Classification - Low— Between phase and neutral, or between phases for non-earthed systems. | ≤ 250 V | Cl. 3.1.1 |
| Voltage Classification - Medium— Exceeding 250 V but not exceeding 650 V. | ≤ 650 V | Cl. 3.1.2 |
| Permissible Voltage Drop— At any point on the supply terminals of the consumer. | ≤ 3% of supply voltage | Cl. 3.2.1 |
| Light/Fan Sub-Circuit - Max Load | 800 W | Cl. 7.3.1 |
| Light/Fan Sub-Circuit - Max Outlets | 10 points | Cl. 7.3.1 |
| Power Sub-Circuit - Max Load | 3000 W | Cl. 7.3.2 |
| Power Sub-Circuit - Max Outlets | 2 points | Cl. 7.3.2 |
| Fixed Wiring Colour - Phase | Red, Yellow, Blue | Cl. 5.1.1 |
| Fixed Wiring Colour - Neutral | Black | Cl. 5.1.1 |
| Fixed Wiring Colour - Earth | Green | Cl. 5.1.1 |
| Flexible Cable Colour - Phase | Brown | Cl. 5.1.2 |
| Flexible Cable Colour - Neutral | Blue | Cl. 5.1.2 |
| Switch Mounting Height— Above floor level, for convenient operation. | 1.3 m | Cl. 5.2.1 |
| Conduit in Plaster - Min Cover | 1.5 cm | Cl. 8.8.1.1 |
| Conduit Saddle Spacing (Horizontal) | ≤ 1.0 m | Cl. 8.2.3 |
| Conduit Saddle Spacing (Vertical) | ≤ 1.5 m | Cl. 8.2.3 |
| Clearance Above Building (Vertical)— For low and medium voltage lines. | 2.5 m | Cl. 6.2.4.1 |
| Clearance From Building (Horizontal)— For low and medium voltage lines. | 1.2 m | Cl. 6.2.4.1 |
| Insulation Resistance (Min)— Between conductors and earth for the entire installation. | 1 MΩ | Cl. 9.1.1 |
| Earth Continuity Resistance (Max)— From earth connection to any point in the conductor. | 1.0 Ω | Cl. 9.2 |
| Max Earth Resistance (General)— For general installations not covered by other categories. | 8.0 Ω | Cl. 10.2.2 (Table 4) |
| Max Earth Resistance (Major Sub-station) | 1.0 Ω | Cl. 10.2.2 (Table 4) |
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
IS 732 is the code of practice for electrical wiring installations — the foundational electrical code in India for low-voltage (LV) installations in buildings. It governs the design, selection, installation, inspection, testing, and maintenance of building electrical systems up to 1100 V (1.1 kV) AC.
Use IS 732 for any electrical installation in: - Residential buildings (single houses, apartments, gated communities) - Commercial buildings (offices, retail, hotels) - Institutional buildings (schools, hospitals, government) - Light industrial premises (workshops, MSME units) - Outdoor installations within building plots (compound lighting, gate motors)
Latest revision: IS 732:2019 is the current edition (the page you searched for was IS 732:1989 — that is the older but heavily-cited revision). The 2019 revision aligns with IEC 60364 international practice. For new installations, always reference IS 732:2019; the 1989 version is largely superseded.
IS 732 is enforced by: - Central Electricity Authority (CEA) Regulations, 2010 — make IS 732 / IS 5572 / IS 3043 the mandatory standards for LV installations - State Electrical Inspectorate — pre-energisation inspection per IS 732 + Indian Electricity Rules - BIS marking (ISI) on electrical accessories required for IS 732 compliance - Bank loan / occupancy certificate requirements in many municipalities
Does NOT cover: - High voltage (above 1.1 kV) — see IS 8478, IS 1255 for HV cables and installation - Specific hazardous-area installations (petrochemical, mining) — see IS/IEC 60079 - Solar PV, EV charging — separate codes (IEC 62548, IS 17017 series)
Wiring systems and methods (Section 5): - PVC-insulated copper conductors as the default (IS 694:2010) — single-core or multi-core - Aluminium permitted for sub-mains in larger sections (≥ 16 mm²) - Wiring methods: surface conduit (PVC or steel), recessed conduit (in walls/slabs), underground armoured cable for outdoor / sub-circuits - Cable trays for commercial / industrial racks
Earthing (cross-references IS 3043): - All metallic equipment / non-current-carrying parts must be earthed - TT, TN-S, TN-C-S earthing systems described - Earth electrode resistance: ≤ 5 Ω for residential; ≤ 1 Ω for industrial/sensitive electronic loads
Protection (Section 6): - Overcurrent protection: MCB/MCCB per IS 8828 and IS 13947 - Earth-fault / leakage protection: RCD/RCCB per IS 12640 (≤ 30 mA for human protection in wet areas; ≤ 100-300 mA for fire protection) - Surge protection devices (SPDs) per IS 16121 (recommended)
Distribution (Section 7): - Main distribution board (MDB), sub-distribution boards (SDB), final circuits - Conductor sizing by current-carrying capacity, voltage drop (≤ 3 %), short-circuit withstand - Diversity factor for total connected load vs maximum demand
Specific room types (Section 8 / Annexes): - Bathrooms / wet zones: Zone-based protection (IP44 fittings within 0.6 m of water; RCD ≤ 30 mA) - Kitchens: dedicated 16 A circuit per heavy appliance (oven, geyser, AC) - Outdoor: IP65 fittings; armoured cable in conduit
Conductor sizing thumb-rules for residential:
| Circuit | Conductor size | Protection | Maximum length (typical) | |---|---|---|---| | Lighting (5 A) | 1.5 mm² Cu | 6 A MCB | 30 m | | 5 A socket outlet | 1.5 mm² Cu | 6-10 A MCB | 25 m | | 16 A power outlet (AC, geyser) | 4 mm² Cu | 16 A MCB + 30 mA RCBO | 20 m | | 20 A heavy outlet (split AC, oven) | 6 mm² Cu | 20 A MCB | 20 m | | Sub-main to flat (5 kW load) | 6-10 mm² Cu | 32 A MCB at MDB | 30 m | | Sub-main to floor (15 kW load) | 16-25 mm² Cu | 63 A MCCB | 50 m |
Voltage drop limit: ≤ 3 % from supply intake to farthest fixture (IS 732 Clause 7.7)
Earthing electrode resistance (IS 3043): - General (no electronic equipment): ≤ 5 Ω - Buildings with computers / electronic equipment: ≤ 1 Ω - Lightning protection (separate electrode): ≤ 10 Ω
RCD trip current ratings: - 30 mA — human protection in bathrooms, swimming pool areas, outdoor sockets - 100 mA — sub-distribution boards (general) - 300 mA — MDB upstream (fire protection)
MCB curves: - Curve B (3-5 In trip): general lighting, resistive loads - Curve C (5-10 In trip): mixed loads, motor circuits, household default - Curve D (10-20 In trip): high-inrush motors, transformers
Cable colour coding (IS 11353): - Phase: red, yellow, blue (3-phase) - Neutral: black - Earth: green / yellow-green stripe
Number of points per circuit (residential thumb-rule): - Lighting: 800-1000 W per circuit - 5 A sockets: ≤ 8 points per circuit - 16 A sockets: 1 point per circuit (dedicated) - AC, geyser: 1 dedicated circuit each
1. Reference IS 732:1989 instead of IS 732:2019. The 1989 version predates RCD requirements, modern earthing systems, and RCD protection in wet areas. New installations must use the 2019 revision. 2. Missing RCD on bathroom and outdoor circuits. Mandatory per current revision; even in old installations, a 30 mA RCBO retrofit is cheap insurance. 3. Single conductor size for entire flat sub-main. 4 mm² for 5 kW load that grows to 8 kW (with split ACs added later) blows up at MCB. Size for design + 30 % future growth. 4. No voltage-drop calculation. End-of-line LED bulbs flicker, motors run hot, geysers underperform. Always check drop ≤ 3 %. 5. Earth pit not maintained / measured. Earth pit dries out over years; resistance climbs from 5 Ω to 50 Ω. Annual earth resistance test mandatory; pour water and salt every 6 months in dry climates. 6. Common neutral for two phases (in 3-phase residential). Neutral overload, conductor heating, equipment failure. Each phase needs its own neutral. 7. Cable in conduit oversized count. IS 732 limits cables per conduit (de-rating from heat). Stuffing 8 cables in a 25 mm conduit reduces ampacity 30 %. 8. Surface mounting in wet zones without IP rating. Bathroom switches and sockets must be IP44 minimum; outdoor IP65. Many residential installations use indoor-rated accessories. 9. No labelling at distribution boards. After 5 years, no one knows which MCB serves what. Mandatory: every breaker labelled with circuit name and load. 10. Earthing of refrigerator / washing machine via 2-pin plug. The third pin is for earth; many old houses still have 2-pin sockets. Replace with 3-pin sockets and verify earth continuity at every receptacle (mandatory at testing per IS 732). 11. No RCBO in solar PV grid-tie installations. Bidirectional current and DC injection require special-grade RCDs (Type B); standard Type A may not trip. 12. DIY work by uncertified electricians. State electrical inspectorate requires licensed electrical contractor for installation; non-compliance is a statutory offence.
Standard MEP design cascade for a residential project:
1. Load calculation — by room/area, demand × diversity factor → total connected load and maximum demand. 2. Single-line diagram (SLD) — supply intake, MDB, sub-DBs, distribution circuits. 3. Cable sizing — per current capacity, voltage drop ≤ 3 %, short-circuit withstand. 4. Protection coordination — main MCCB > sub MCCB > circuit MCB; selectivity to avoid main trip on branch fault. 5. Earthing system — TN-S or TT; pit design per IS 3043; at least 2 pits in parallel for redundancy. 6. Lightning protection — air terminal, down conductor, earth electrode per IS 2309 (not strictly part of IS 732 but companion). 7. Distribution boards layout — accessible, labelled, future-expansion 20 % spare ways. 8. Wiring details — conduit routing, switch heights (1.4 m typical), socket heights (0.3 m wall sockets, 1.4 m kitchen counter, etc.). 9. Specifications (BOQ): - Cables: `PVC insulated copper conductor, 1.5 mm² to IS 694:2010, FRLS grade for confined spaces` - MCB: `IS 8828:1996, Curve C, 6 kA breaking capacity, ISI marked` - RCBO: `IS 12640, 30 mA sensitivity, Type A` - Switches/sockets: `Modular, ISI marked, 16 A 3-pin for power, 6 A 5-pin for general` 10. Pre-commissioning testing (mandatory per IS 732 Section 9): - Insulation resistance (≥ 1 MΩ per circuit at 500 V DC megger) - Earth continuity (≤ 0.5 Ω from accessory earth pin to earth pit) - Earth electrode resistance (≤ 5 Ω) - RCD trip test (manual button + actual trip-current verification) - Polarity check at every socket 11. Inspector approval — state electrical inspectorate inspection before energisation. 12. As-built drawings — handed over to owner with circuit-to-MCB mapping.
IS 732 sets the baseline; for high-end residential and commercial, add: BMS integration, smart-home control, energy meters per circuit, solar PV / inverter hybrid, EV charging.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Wire Colour - Neutral Conductor | Black | Blue | BS 7671 / IEC 60445 |
| Wire Colour - Protective Earth Conductor | Green | Green-and-Yellow bicolour | BS 7671 / IEC 60445 |
| Wire Colour - Single Phase Line | Red | Brown | BS 7671 / IEC 60445 |
| Nominal Single-Phase Voltage | 240 V | 230 V (+10% / -6%) | BS 7671 (CENELEC Harmonization) |
| RCD Protection for General Socket Outlets | Recommended for specific high-risk applications (e.g., wet areas). Not mandatory for all general-purpose outlets. | Mandatory 30mA RCD protection for virtually all socket outlets (≤32A) used by ordinary persons. | BS 7671:2018+A2:2022 |
| Minimum Copper Conductor Size for Power Circuits | 1.5 sq mm for socket outlets. | 2.5 sq mm for general purpose socket outlets (ring or 20A radial). | BS 7671 (common UK practice) |
| Definition of Bathroom Safety Zones | General guidance provided without specific numbered zones. | Specifies detailed Zones 0, 1, and 2 with strict rules on IP ratings and equipment. | IEC 60364-7-701 / BS 7671 |