Electrical in Construction

⚡Electrical Works in Building Construction: Key Standards and Practices

Electrical systems are a critical component of any building project, directly impacting safety, functionality, and energy efficiency. High-quality electrical installations ensure reliable power distribution, secure operations, and long-term performance. Below is a detailed overview of essential electrical works in construction, aligned with best practices and relevant Indian Standards.

🔌 Electrical Wiring

• Purpose: Facilitates safe and efficient distribution of electrical power throughout the building.
• Materials: Use high-quality copper conductors and PVC-insulated cables that resist fire, moisture, and mechanical stress.
• Compliance: Wiring systems must adhere to applicable Indian Standards and safety codes.
• Protection Devices: Circuit breakers, switches, and other protective components should be selected based on appropriate ratings and specifications.

🌍 Earthing

• Function: Protects occupants and equipment from electrical faults by safely dissipating fault currents into the ground.
• Design: Includes a network of conductors buried in the earth and connected to the building’s electrical system.
• Standards: Must be designed and installed to ensure low earth resistance and high conductivity, in line with national safety standards.

💡 Lighting Systems

• Fixtures: Install energy-efficient lighting such as LED lights, CFLs, and other suitable options based on building requirements.
• Control Devices: Use appropriate switches, dimmers, and automation systems for efficient lighting control.
• Safety: All lighting installations must comply with relevant safety codes and electrical standards.

🔋 Power Backup Systems

• Purpose: Ensures uninterrupted power supply to critical loads during outages.
• Options: Includes generators, UPS systems, and inverters.
• Design Considerations: Must include transfer switches, voltage stabilizers, and protective devices with suitable ratings.
• Installation: Should follow standard procedures for power supply, grounding, and control wiring.

🔥 Fire Alarm Systems

• Function: Detects and alerts occupants in case of fire emergencies.
• Components: Includes smoke detectors, heat sensors, control panels, and alarm devices.
• Compliance: Must meet all applicable fire safety and electrical standards for reliable operation.

🛡️ Security Systems

• Purpose: Enhances safety and surveillance within the building.
• Systems: Includes CCTV cameras, access control systems, and intrusion detection devices.
• Design: Must be planned with appropriate sensors, control panels, and power supply arrangements.
• Standards: All components should comply with national safety and performance standards.

⚡ Lightning Protection System

• Objective: Safeguards the building and its occupants from lightning strikes.
• Design: Involves installing conductors and electrodes on exposed surfaces like rooftops.
• Performance: Must ensure low impedance and high conductivity to effectively channel lightning energy into the ground.

🌬️ HVAC Systems

• Scope: Includes heating, ventilation, and air conditioning systems that affect indoor comfort and energy usage.
• Components: Chillers, air handling units, ducting, and control systems.
• Electrical Integration: Requires proper power supply, grounding, and control wiring.
• Compliance: Must meet all relevant electrical and safety standards.

🛗 Elevators and Escalators

• Application: Essential for vertical transportation in multi-story buildings.
• Equipment: Motors, controllers, safety devices, and control panels.
• Installation: Electrical systems must be designed for reliable operation, including power supply and grounding.
• Safety: Must comply with national standards for elevator and escalator systems.

⚙️ Electrical Equipment

• Examples: Pumps, motors, compressors, and other machinery used in building operations.
• Design: Includes proper sizing, location, and capacity planning.
• Electrical Setup: Requires dedicated power supply, grounding, and control wiring.
• Standards: Installation must follow all applicable electrical codes and safety regulations.

📌 Final Note

The scope and complexity of electrical works vary depending on the building’s size, type, and intended use. It is essential to follow relevant Indian Standards and consult qualified electrical engineers and contractors to ensure safe, efficient, and compliant installations.

🧠 What to Remember

• Use high-quality materials and certified components.
• Ensure proper earthing and lightning protection.
• Install energy-efficient lighting and reliable power backup.
• Integrate fire alarms and security systems for safety.
• Design and install HVAC, elevators, and other equipment with precision.
• Always follow national electrical and safety standards.

These practices ensure that electrical systems in buildings are safe, efficient, and built to last.

 

Circuits
1.     Load more than 1 KW shall be controlled by suitably rated MCB and cable size  shall be decided as per calculations.    2.    It is recommended to provide double pole MCB in proper enclosure as power  outlet for window type AC units, geysers etc.   3.   Power/light DBs shall be marked ‘P’ and ‘L’ respectively.
Lighting Circuit	Per Circuit Not more than 10 Points of Lighting or Total 800 Watt which is less
Power Circuit	For Residential Per Circuit  upto       - 2 No of 16A Plug Socket                                          - 3 No of 6A Plug Socket                                              - 1 No 16A and 2 Nos  6A Plug Socket
Power Circuit	For Non Residential Per Circuit only 1 No of 6A/16A Plug Socket
Plug Socket	In Residential Wiring ,wiring of Socket outlet shall be done by copper Cable only
Size of Wire	For Lighting Circuit Smallest size of conductor shall be 1.5 Sq.mm For Power Circuit Smallest size of conductor shall be 4 Sq.mm Power circuit rated  :  More than 1 KW, Size as per calculation
Classification	Residential         -   GROUP A  ( For Type I, II, III and Hostels),                   Conduit – 2.5 Mtr., Cable – 3 Mtr. GROUP B  ( For Type IV and Above, Barracks)             Conduit – 3.5 Mtr., Cable – 4 Mtr.  Non Residential  -   GROUP C   ( For All Types- Offices, Hospitals, Lab, Library, etc.)               Conduit – 4.5 Mtr., Cable – 5 Mtr.               (Also used in Twin Control) ·         5 % Wastage already taken in Rate.
Conduit Size	20 mm, 25 mm, 32 mm, 40mm can be used (As per requirement)
GI Box	1 Module        - 75mm x 75mm 2 Module        - 75mm x 75mm 3 Module        - 100mm x 75mm 4 Module        - 125mm x 75mm 6 Module        - 200mm x 75mm 8 Module        - 125mm x 125mm 12 Module       - 200mm x 150mm
Metal Box	60 mm deep can be used
MCB	SP     - 6A to 32A, 240/415V, 10 KA, “C” Curve SPN   - 6A to 32A, 240/415V, 10 KA, “C” Curve DP     - 6A to 32A, 240/415V, 10 KA, “C” Curve TP     - 6A to 32A, 240/415V, 10 KA, “C” Curve TPN   - 6A to 32A, 240/415V, 10 KA, “C” Curve
TP&N MCB	(31, 63, 100, 125, 160, 200, 315, 400 )A
MCCB Rating 3 Pole	(100,125,150,200,250,315,400,500,630,800)A; (16, 25, 35, 50) KA
MCCB Rating 4 Pole	(100,125,200,250,400,630,800)A; (30,36,50) KA
Isolator	DP     - (40, 63)A 4P     - (40, 63, 100)A
RCCB  (30mA)	DP     - (25, 40, 63)A 4P     - (25, 40, 63)A
MCB DB	(6, 8, 12, 16 ) Way Double Door – Single pole & Neutral (SPN) Horizontal Type: Way Double Door –Three pole & Neutral (TPN) 4 (4+12)  6 (4+18)  8 (4+24) Vertical Type: Way Double Door – Three pole & Neutral (TPN) 4 (4+12)  8 (4+24) 12 (4+36)
Isolator	DP     - (40, 63)A 4P     - (40, 63, 100)A
TPN Industrial Type Socket	·         TPN (20, 30 )A ·         Industrial type Socket Outlet with Plug top and metal  chained cover ·         TP MCB : 6A to 32A, 240/415V, 10 KA, “C” Curve
Rising Mains	·         200 A (Isc – 15 KA for 1 Second) ·         300 A (Isc – 20 KA for 1 Second) ·         400 A (Isc – 25 KA for 1 Second) ·         600 A (Isc – 45 KA for 1 Second) ·         800 A (Isc – 50 KA for 1 Second)
Tap OFF Box	TPN Tap OFF Box ·         One Way - (16, 32, 63, 200, 315, 400)A ·         Two Way – (16, 32,63)A ·         Four Way – (16, 32,63)A ·         Six Way - (16, 32,63)A ·         Eight Way - (16, 32,63)A
Colour Coding	Following colour coding shall be followed in wiring: Phase       :  Red/Yellow/Blue.(Three phase wiring)     Live          :  Red (Single phase wiring) Neutral    : Black Earth       : Yellow/Green.
Plug Socket
1.     The third pin shall be connected to earth through protective (loop earthing)  conductor.    2.    2 pin or 5 pin sockets shall not be permitted to be used,    3.    Rating above 1KW shall be of industrial type with associated plug top and controlling MCB.
Plug Socket	6A - rated at 100W 16A - be rated at 1000W		Unless the actual values of loads are specified.
	5A/6A or 15A/16A Socket shall be installed at following heights:                                                       For Non Residential building 23cm above  floor For Kitchen 23cm above  Platform and away from stove and sink.  For Bathroom not Socket is provided, MCB/IC will be 2 metre from fixed appliance and at least 1 metre away from Shower
IS Standard	GI/MS Pipe                                    IS: 1239(Part-1)/90 MS Conduit pipe                            IS:9537/1993 (I & II) PVC Conduit pipe                          IS:9537/1993 Switches  IS: 3854/1988 Plugs & Sockets                            IS: 1293/1988 Ceiling rose                               IS: 371/1979 Lamp holder Bakelite                 IS: 1258/1979 Bell Buzzer                                 IS:2268/1988 or latest MCB     IS: 8828/1996 MCCB    IS: 13947(Part-1&5/Sec1)/1993 RCCB  IS: 12640(Part-1)/2000 HRC fuse                                       IS: 13703(Part-2/Sec1)/1993 SFU(Switch Fuse Unit)                 IS: 13947(Part-3)/1993 Wires      IS: 694/1990 XLPE Cable 11/33kV grade           IS:7098(Part-2)/1985 11 KV Jointing   KIT                       IS: 13573/1992
Switch Board /  D.B
1.     Switchboards are to be located in common areas like corridors, lobby etc. and not to be located in locked room.   2.    Switch box or regulator box shall be made of metal on all sides, except on the front. In the case of cast boxes, the wall thickness shall be at least 3 mm and in case of welded mild steel sheet boxes, the wall thickness shall not be less than 1.2 mm (18 gauge) for boxes upto a size of 20 cm x 30 cm, and above this size 1.6 mm (16 gauge) thick MS boxes shall be used.   3.     Follows
Operating Rod	Operating Rod/Handle of Distribution Board at the height of min 2 metre
D.B Clearance	Clear Distance in front of Switch Board/D.B shall be min 1 metre
Switch Box	Switch Box or Regulator Box shall be mounted with their bottom 1.25 metre from floor level
Fan
Fan Box		1.     For Fan Hook in concrete roof 12mm dia MS Rod in ‘U’ Shape, horizontally Leg at Top at least 19 cm on either side. 2.    Circular Box Type Fan Clamp- 16SWG MS Sheet  As Per CPWD 10.18 (CIVIL):  Providing and fixing circular/ Hexagonal cast iron or M.S. sheet box for ceiling fan clamp, of internal dia 140 mm, 73 mm height, top lid of 1.5 mm thick M.S. sheet with its top surface hacked for proper bonding,top lid shall be screwed into the cast iron/ M.S. sheet box by means of 3.3 mm dia round headed screws, one lock at the corners. Clamp shall be made of 12 mm dia M.S. bar bent to shape as per standard drawing. Specification: Civil Volume 1 ; 10.14
Capacity of a Ceiling fan		=55D m3/min ,D= the longer dimension of a room
Height of fan blades above the floor		= (3H + W)/4, where H is the height of the room, W is the height of work plane.
Minimum distance between fan blades and the ceiling		0.3 metre.
Ceiling Fan Rating		·         60W, Energy Efficient fans with BEE 3-5 star rating or complying with IS 374: 1979, shall be used. The minimum service value of fans shall be 3.5 m3/min/W and air delivery 200 m3/min.    ·         BEE 5 star rated Ceiling fan with Brush Less Direct Current (BLDC) motor
IS Standard		Ceiling Fan          -  IS: 374/1979 Exhaust Fan       -  IS: 2312/1963 Electronic fan regulator -  IS:11037/1984
Junction Box
Junction Box	Depth of Junction Box shall be min 65mm in slab and other places as per IS 2667 : 1988
Fish Wire
Fish Wire	GI fish wire of 1.6mm/1.2mm (16/18 SWG) shall be used along with the laying of the recessed pipe.
Earthing
Items Required	GI Pipe Earthing ·        GI Pipe 40mm (Medium Class) – 4.5 Mtr ·        Cover Plate hinged to frame with locking Arrangement ·        40mm to 20mm Reducer ·        Funnel ·        GI Nuts Through Bolts with washer ·        Charcoal – 64 Kg ·        Salt- 5 Kg GI Plate Earthing ·        GI Plate– 600mm x 600mm x 6mm Thick ·        GI Pipe 20mm (Medium Class) – 2.7 Mtr ·        Cover Plate hinged to frame with locking Arrangement ·        Funnel ·        GI Nuts Through Bolts with washer ·        Charcoal – 96 Kg ·        Salt- 5 Kg Copper Plate Earthing ·        Copper Plate– 600mm x 600mm x 3mm Thick ·        GI Pipe 20mm (Medium Class) – 2.7 Mtr ·        Cover Plate hinged to frame with locking Arrangement ·        Funnel ·        GI Nuts Through Bolts with washer ·        Charcoal – 96 Kg ·        Salt- 5 Kg
GI Wire	6 SWG (0.147 kg/mtr)
Copper Wire	8 SWG (0.117 kg/mtr)
GI Strip	25mm x 5mm (1.0 kg/mtr)
Copper Strip	50 mm x 5mm (2.30 kg/mtr)
Lightning Conductor
Items Required	Lightning Finial      ·         Lightning Finial (GI) -25mm Dia x 300 mm Long    ·         Steel Fastener - 6mm x 75mm  GI Tape - 20mm x 3mm thick  (0.461 kg/mtr)           - 32mm x 6mm thick  (1.475 kg/mtr)  GI Saddle - 20mm x 3mm thick  PVC Fastener – 40mm long  Iron Screws - 35mm x 6mm thick
MV/HV Cable Laying
Items Required	Direct in Ground: For 100 Metres    ·         Brick  - 874 Nos + 44 Wastage(5%) = 918 Nos    ·         Fine Sand – 8.76 CUM  For Additional one Nos.    ·         Brick -  874 Nos + 44 Wastage(5%) = 918 Nos    ·         Fine Sand – 5.0 CUM On Wall Surface:  Upto 35 Sq.mm    ·         GI Saddle - 19mm x 0.55mm for Conduit  Above 35 Sq.mm    ·         Nuts & Bolts - 32mm x 8mm    ·         Flat Iron – 20/25/40mm x 3mm    ·         Steel Fastener - 6mm x 75mm
MV Cable Jointing & End Termination
Items Required	·         Brass Compression Gland for 2 x 6 Sq. mm     (19 mm) 1.1 kv cable & Al lugs for 6 Sq.mm cable. Same for Another Size    ·         Jointing Kit
Installation Testing & Commissioning Charges as Per DSR 2018
·         1.41 , 1.42 – For Lighting Fixture ·         1.44, 1.45  – For Fan