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Technical specification for electrical wiring / panels / switch gear


The  electrical installation is to be carried out in conforming  with  the      requirements  of the Indian Electricity Act, l9l0 as amended up  to  date and  the Indian Electricity Rules, l956 framed there under,  the  relevant regulations of the Electric Supply Authority concerned, and also with the  specifications  laid down in the Indian Standard I.S. 732 - l963 Code  of  Practice  (revised) for Electrical Wiring Installations (system  voltage  not  exceeding  650 volts) and I.S. 2309-1969 Code of  Practice  for  the  protection of Buildings and Allied Structure against Lighting and IS 3043  -  Indian  code  of  Practice for Earthing.  The wiring should  also be according to the I.S specifications, NEC, Local Government Body.   Contractor having valid Electrical Contractor Licence of the State should execute the electrical installation job.


The materials, fittings, appliances, used in electrical installations, should conform to Indian Standard Specifications wherever these exist.  A list of approved materials should be explored and to be attached. Materials not included in the list should be  got  approved  by  the  owner encharge.  

  1. Main Switch Gear 

Iron clad switch fuse and isolator units should conform to relevant I.S. Standard.  The quick make and break mechanism should  be self interlocked with the cover. In "Off" position there must be two breaks per pole.    Main switch gear should be properly earthed with two numbers conductors for medium voltage and one number of low voltages.

  1. Bus bar Chamber (B.B.C) 

Bus bar chamber should be enclosed type  fabricated  from  rust proofed  14/l6 SWG sheet steel on angle iron frame and provided  with  sheet steel  detachable front cover and undrilled  detachable  end plates,  suitable  for  mounting on wall or angle iron  floor  stand  and painted with high quality enamel paint. G.I. bolts and nuts should be used for assembly with suitable packing materials to ensure dust proof finish. Meters should be provided on suitable sheet steel boxes. The depth of B.B.C. should be 250 mm (minimum). Minimum clearance of phase bars to earth should  be 1 inch and between bus bars should  be minimum 1.25 inch.    H.C.  (High conductivity) copper bus bars properly tinned are to be rated at l.3 Amp per sqmm and Aluminium bus bars (wrought aluminium alloy strip) conforming to relevant I.S. specification at 1.0 Amps per sqmm.   Although a calculation should be attached considering the safety factor. Neutral bus bars are to be rated to carry 100% of phase current upto 200A and 60% for higher.  The insulator like DMC/SMC should be used for supports and proper dielectric and mechanical strength with colour coded for identification of Phase with PVC sleeves of 1.1 KV grade throughout the length.  

Tagging/marking should be done for identification of switches as directed.  The contractor should submit dimensioned drawing of the board with the physical position of the switches and other components for approval before the same is fabricated.    There should be two nos. of Earth Terminals. Suitable Danger Board should be provided.

  1. Interconnection in B.B.C,  Switch Fuse, Meters   

For ratings above 200 Amps these should consist of insulated copper strips of adequate section considering current density.  For rating below 200 Amps PVC copper cable of appropriate size, terminating in tinned copper sockets may be used considering 1.5 Amp/sq.mm for copper & 1.0 Amp/sq.mm for aluminium. The above are to be enclosed either in sheet metal trunking or conduits so that no part is exposed.  

  1. Distribution Boards  

Distribution Boards  should be enclosed metal clad type with  hinged lids in accordance with I.S. 2147 - 1952 and 2675 -  l966  and B.S.  2l4  and  should  be of welded construction and fabricated  from  rust proofed  sheet steel and finished with anticorrosive stove  enamel  paint and   have   provision   for   fixing   on   wall   and   have  earthing terminals/terminals.    Power Distribution Boards (415 volts TPN) should be constructed from 14/l6 SWG sheet steel and Branch Distribution Boards (230 volts SPN from l8 SWG sheet steel).    The MCB should be mounted on Din rails supports of proper dielectric & mechanical strength. If fuses/fuse banks are used these should be mounted on moulded DMC/SMC supports of proper dielectric and mechanical strength. TPN units should have phase separation barriers.    Cables should be connected to a terminal by crimped lugs.    Where  two  or  more D.B's feeding low voltage circuits  are  fed  from different  phases  of  a medium voltage supply, these D.B's  should   be installed  at least one  metres  apart  or  otherwise  in  a different direction to prevent access to the both DBs at a time.    All three phase power distribution boards should be properly earthed as per relevant I.E. rules and provided with suitable Danger Board written in local language and second language as applicable. All SPN B.D.B's should  be properly earthed with one  number 8/l0 SWG galvanised iron wire each or with insulated copper PVC wire of adequate ratings in case of concealed wiring as per the specifications. 

  1. Switches  

The switches should be modular/Piano type as approved, single/double pole, concealed mounting type as required, with quick make and quick break mechanism and rated at 5 amps for light point wiring.  Modular/Piano type, 15 amp switches should be used for power plugs. Where the supply is derived from a three phase four wire source, the distribution should be done on the single phase two wire system.  All branch switches should be placed in the line conductor of the circuit and no single pole switch or fuse should be inserted in the neutral conductor of the circuit.


Socket outlet should be 5A, 3 pin or 15A, 6 pin as required.  This should be all insulated, surface or concealed mounting type and should be controlled by a switch.

The switch controlling the socket outlet should be on the “Live” side of the line.  The third pin should be connected to the earth.  For industrial premises, metal clad heavy-duty socket outlet should be used.



Lamp holders for the use of bracket etc. should be of brass and should have not less than 12mm dia, nipple, and all those for use with flexible pendants should be provided with cord grips.  All lamp holders should be provided with shade carriers.  Lamp holders in case of outdoor light fixtures should be made of porcelain.



Ceiling fans and air circulator should conform to Indian Standard Specifications.  The fans should be supplied with all standard accessories like down rod of suitable length or standard length to attain the desired mounting height, blades, regulator and capacitor etc.  The tenderer should mention the number of blades, type of regulator, power consumption at low and maximum speeds, double or single ball bearing. 


The performance of the exhaust fans should be in accordance with stipulation of IS: 2312.  All the fans should be robust in design and construction and should be supplied complete with wall bracket/clamps, gravity louvers, and propeller blades, motor of adequate size.  The sweep and air displacement capacity should be as per BOQ.


  1.  LED Tube Fittings
  1. All fluorescent fitting supplied should  conform Indian standard and should  be complete with all standard accessories like driver, surge arrester, clamp etc.
  2. The type of enclosure provided for the fittings should be as specified in the billing schedule and the working drawings.
  3. The material of construction for fittings used for outdoor installations and for use in the work sheds should be such that they should withstand the atmospheric condition in that area.
  4. Lamp holders used should be fully shock proof, spring loaded, and rotary type to ensure positive lamp locking.  It should also not be possible to touch live parts of the lamp-holder both after the lamp has been taken out and during the insertion or removal of the lamp.
  5. Pl see technical specification of LED light



Cables should conform to I.S-692, IS-7098, IS-1554 (Part-I) 1964 and IS 694-1990 or latest. Conductors of all cables except for flexible cables should be of aluminium, unless specified otherwise.

  1. Flexible wire  

 Conductors of flexible cables should be of copper. The minimum size of core acceptable is 1.5 sq.mm for lighting circuit and 2.5 sqmm for power circuit.   

  1. Installation Of Main Switch Board, Db's Mains, Submains,  Distribution wiring to Individual Points  

 The exact positions of all main switch board, DB's and all runs of mains and sub mains, and distribution wirings to individual points including the exact  position  of all light fittings and switch boards should   be  first marked  on the buildings and should  be approved by the  owner representative before actual commencement of the work.    The D.Bs should generally be installed at a height of 5 feet from floor level. 

  1. Installation of Switch boards   

 These should be installed at a height of l.3 mtr (4'-3") and above the floor level. The power point should be installed a height of 12 inch from floor level.

  1. Installation of fluorescent light fittings :   

Where these are suspended from ceiling by two down rods, or fixed  to ceiling/beam directly, at least one fixing to the ceiling/beam should   be made  with  Mechanical/Metal fasteners. Electrical drill only should   be used while making holes for the fasteners which should   be capable of sustaining at least 15 kg of dead weight.    The down rods and accessories should be painted with approved paint without involving extra cost.    Unless otherwise specified these should be suspended 2.60 M (8'-6") above the floor or as per direction of Owner to match interiors.  

  1. Installation Of Socket Outlets   

No socket outlet should be provided in the bath room at the height less than l30 cms (4'-3") from the floor.    No switches should be provided inside the bath rooms, unless approved by the Engineer-inCharge.    Socket  outlet at locations other than bath rooms should  be either 25  cms (l0") or 130 cms (4'-3") from the floor.  


a) Drawings of electrical panels is to be got approved by the owner/Architects.    

b) Panels should be inspected at works and approved by the owner/Architects prior to despatch.     c) Panels should be tested for insulation resistance and HV withstand test. Factory test certificates should be obtained.

d) If TPI (third party inspection) is kept in clause, Inspection should be done by TPI. Material should be dispatched after TPI clearance.



 All   installation or an addition to   an   existing installation should be tested before taking  into service.  The following tests should   be carried out by the contractor in presence of the    Owner’s/Architect’s representative. 

  1. Polarity of switches 

It must be ensured by test that all single pole switches have been fitted on the live side of the circuits they control.  

  b) Insulation Test:   

 i) By applying a 500 volt megger between earth and the whole  system  of conductors or  any  section thereof, with all fuses  in  place  and  all switches  closed, all lamps in position or both  poles of installation otherwise  electrically connected together. The result in mega ohm should not be less than 50 divided by the number of points on the circuit and should not be less than 1 mega ohm.

 ii) Between all conductors connected to one phase and all such conductors connected to the neutral or to the other phase conductors of the supply after removing all metallic connections between the two poles of the installation and switching on all switches. The insulation resistance should be as in (i) above.   

 c) Earth continuity Test

     The earth continuity conductor including metal conduits, and metal sheaths of cables in all cases should be tested for electrical continuity. Electrical resistance of the above along with the earthing lead  but excluding any resistance of earth leakage circuit breaker, measured  from the  connection  with  the  earth electrode to any  point  in  the earth continuity conductor in the completed installation should  not exceed one ohm.   

 d) Earth Resistance Test  

   To  ensure  effectiveness  of  installation earth,  the  value  of  earth resistance should  be within 5 ohm for installation capacity upto 5 KW  and one ohm for installation of higher capacity. 

 The completed work should be taken over only if the results obtained in above tests are within the limits mentioned above, and in accordance with I.E. Rules.



  a) Before fixing all switches, fittings etc. these should be produced before owner/plant in charge and get approved.   

 b) All metal switch boards and switch/regulator boxes to be used in work should be painted with two coats of anti rust primer (red oxide paint) prior to erection. After erection these should be again painted with two coats of enamel paint of approved quality and shade.  

  c) Before execution of any portion of conduit work for wiring a neat proper layout should be made out by the contractor and got approved from site engineer.  For this purpose, contractor is advised to get acquainted with the layout drawings of the Consultant/Interior Decoration Contractor.   

 d) While laying the conduits for concealed wiring in the ceilings/beams/columns/walls/ partitions/modular furniture etc, the contractor must ensure that  all the  inlets and both ends of the conduits are plugged to stop entry of foreign materials  so that  no difficulty arises during drawing of wires later .  

  e) Damage  to any fitting during erection and before  handing  over  the installation  by  contractor  should   be set  right  or  replaced  by  the contractor.  

  f) Caution Board of proper size wherever required, should be provided, as per I.E.E. regulations for which no extra payment will be admissible.   

 g) Any repairs done to wall etc. should match with  the  surrounding surface  otherwise same will be got done through Building Contractor  at the cost of the Electrical Contractor.  

  h) Earthing Installation should be done in the presence of site engineer or his representative.  

  i) The installations should not be energized without adequate earthing.   

 j) Distribution Fuse Boards should be provided with neat lettering in block letters with paint and for the points connected to each fuse way of the D.B’s for which no extra payment will be admissible.  

k) Completion Drawings: The contractor should  submit final drawing with final  bill.   The drawing may be in soft copy and hard copy.  

Plan (as per structural drawing) of each floor-

  • Location of Main Switch Board, Distribution boards (with the  circuit numbers controlled by them).
  • The runs of mains and submains.       
  • Location  of  lights, fans, wall  sockets,  other  power  consuming devices  together  with type of fittings and fixtures  including  circuit numbers.      
  • Position of Lightning Conductors and route of running conductor.        
  • Position of Earthing Stations for light and power and Lightning Conductor Installation.        

Following information is to be given on all the drawings:          

a) Name of work with job no.

 b) Date of completion   

c) Name of Place  

d) Name and Signature of Contractor  

e) Scale of Drawings. 

             f) Cable route should be marked on site plan with measurements from permanent structures.  



  1. GENERAL   

All Medium Voltage and Low Voltage PVC insulated and armoured/unarmoured cables should conform to IS 1554 Part-I-1964 and of 1,100 volt grade.     Old and used cables must not be used for installation. Only one make of cable should   be used. All cables brought to site must be tested and got approved by the  site engineer or plant manager  before  these  can  be  laid.  The cables should   be despatched to site on wooden drums with ends sealed. Exact lengths should   be determined by the Contractor after measurement at site.    The underground installation of cables should be generally conforming to  I.S. 1255-1967,  Code of Practice for installation and maintenance  of  underground cables (upto including 33 KV).


  a) Inside Building     

 Cables should be laid on walls/ceiling/structure, unless specified otherwise, with  M.S.  brackets and suitable clamps or over claw  type  aluminium  cleats fixed  on  M.S.  Brackets spaced not more than 1m apart.  G.I Bolts of suitable sizes are to be grouted on the wall properly for fixing the brackets.  

  b) Minimum bending radius permissible is 12D for MV Cables and 20D for HV cables.  At joints and terminations, the individual core of multicore cables should never be bent so that the radius is less than 15 times the diameter over the insulation. Avoid cable jointing between two terminal points.  


   All cable  joints should  be carried out by experienced and  Licensed  jointers under strict supervision. Electro plated brass cable glands, aluminium/tinned copper cable sockets and approved jointing materials must be used. The  price for  cable  jointing  and finishing the ends of the cable  should   include  all materials and should  also provide for tools and plants for the work. The cable armouring  is  to  be properly terminated. All  cable  accessories  and  other associated  materials  should  conform to Indian  Standard  Specification  where applicable. Proper earthing of cable glands and armouring should  be included in the job. 


 All cables should be tested for insulation resistance with  megger  - 2500V for HT Cables and 500 V  megger for LV Cables, before installation.    After installation and end termination, the cables should be again subjected to the above test. Insulation value for HT Cables should not be less than 100 mega ohms and for LT Cables 1.0 mega ohm.    After laying and jointing, the HV Cables should be subjected to high  voltage pressure  test  before commissioning, the test voltage being  as  specified  in I.S.1255-1967 or latest


 Before the completed installation is put into service or handed over to Owner, the installation is to be subjected to the above tests to the satisfaction of the  site engineer  or plant manager.  The completed work will be taken over only if the results are acceptable to the Owner/Architects/Consultant.


The installation should generally conform to IS 3043 - Indian Standard Code of Practice for Earthing, as amended upto date.  


a) Plate Electrode    

 Where plate electrode for earthing is to be employed, the size of the plate should not be less than 0.6 m x 0.6 m x 6 mm thickness for G.I plate and 0.6 m x 0.6 m x 3mm thickness in case of copper plate.    

 The plate should be buried vertically with the top at a minimum of 4.0 M below the ground level for sandy soil and 2.0 M below the ground level for normal soil. In order to place the same at the prescribed depth, the dimension of pit to be excavated should be 0.9 m x 0.9 m x 3 M deep. The plate should be placed in position by the contractor only after the inspection of excavated pit and approval is obtained from the Engineer.  

   One no. 50 mm x 6 mm G.I flat (for electrical installation) or one no. 25 mm x 6 mm GI flat (for Lighting conductor) should be connected to the plate at two points by means of 65 mm long 12 mm dia galv bolts, nuts and galv washers. In case of copper plate copper flat of not less than 32 mm x 6.0 mm should  be used as the earth lead. Brass bolts, nuts and washers should  be used for fixing. All other details should  be in accordance with IS 3043-1987.  No joint on the earth lead conductor is permitted. Every care be taken to ensure that the ends of the wire/flats have been securely clamped by the bolt on cleaned surface of the plate and established a good electrical contact.     

 After placing the plate the earth lead conductor should  be protected by means of a continuous length of G.I pipe (Class-B) having 50 mm dia bore or depending upon the  size  of  the  lead,  right  from  the  plate  upto  a height of 0.60 metre (2 ft) above ground level. The whole length of pipe should be filled with bituminous compound of approved make and brand. The molten compound should  be poured from the top end the pipe and topped upto overflowing.   

  The plate electrode should  have a 50 mm galvanized iron water pipe buried vertically and adjacent to the electrode and reaching upto the center of the plate. The upper end of the pipe should  be atleast 5 cm above the bottom of the inspection pit and with wire mesh, funnel, etc as per IS specification.   


The inspection pit for the earth station should be approx 0.56 M x 0.56 M  (1'-10"x1'-10") outside dimensions and approx 0.45 M (l'-6") deep when  completed, having 5" thick cement brick work with lst class bricks in cement mortar (6:l) both inside and outside plastered 19 mm (3/4") thick and neatly cemented  l.60 mm  (l/16") thick, both inside, outside and top. The opening on top  should   be provided with a C.I. ring with lockable cover fixed flush with ground surface.    All the excavations should  be duly back filled, dressed and rammed.


  Electrodes should be buried at least 2 M away from the building pole or object  to  be earthed. However, earthing electrodes for  Lightening conductor  installations should be as close to the down conductors as possible.    Electrodes, when installed in parallel, should  not be placed less than  length of one electrode apart and  preferably placed at distances greater than twice their lengths. 


  a) Galvanised M.S. Flat    

 The bus bar should  be of suitable size and length, as specified in the  Schedule of Items, heavily galvanised and having adequate number of drilled and  tapped holes  25  mm  apart, complete with G.I. bolts,  nuts,  washers  for  securely connecting  the earth leads and earth continuity conductors. The bus bar  should  be fixed on wall, having clearance of 6 mm  from wall with spacing insulators with at least 13  mm  (l/2") G.I. rag bolts spaced about 0.46 M apart.  

  b) Copper Flats:      To be used, as specified, in the Schedule of Items, where   earthing requirements are more stringent. Brass bolts, nuts washers should be used for connections. 

  • Major power station= 0.5 Ohm.
  • Major Sub-stations= 1.0 Ohm
  • Minor Sub-station = 2 Ohm
  • Neutral Bushing. =2 Ohm
  • Service connection = 5 Ohm
  • Medium Voltage Network =2 Ohm
  • L.T.Lightening Arrestor= 4 Ohm
  • L.T.Pole= 5 Ohm
  • H.T.Pole =10 Ohm
  • Tower =20-30 Ohm




This work generally involves laying of 5/10/20/50/ pair armoured cable from Junction Box to substation and termination at both the ends in the krone module junction box.  


Lying of 2 pair /5 pair cables through separate conduits/trenches/floor truncking (where ever necessary in PVC Pipes) and termination at work stations, cabins and other locations as indicated in the drawing and also as per the direction of client/ Architect. The contractor will ensure that each and every point is identified (with identification tags) and tested for connecting existing EPABX system.




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