Method for Installation of Conceal & Surface Conduits (Part-2)


4.Filling Chasing Area:

  • All grooves, chases shall be properly filled and concreted and finished up to the wall surface before plastering of walls is taken up. The conduit boxes, accessories, joints, etc. shall be laid along with the conduits. The chases shall be sufficiently deep and properly filled with cement mortar.
  • Where conduits pass through expansion joints in the building, adequate expansion fittings or other approved services shall be used to take care of any relative movement. As far as possible, chasing of wall to embed the conduits to be avoided.
  • Chasing is filled by Cement mortar 1:5 ratio(1 portion of the cement+5 portion of sand) shall be used for patchwork in chased area and its surface is rough so main plaster will easily joint on chasing area.
  • Curing shall be carried out for a minimum of three days.
  • Make sure the conduits are not visible from outside their route which could lead to improper plastering.

5.Wire Mesh:

  • After chasing area is filled by mortar, Chicken (wire) mesh and GI nails shall be applied on chasing area to avoid hair crack in plaster.
  • Width of Chicken Mesh is slightly larger than chasing Area. After installation of Chicken mesh final Plaster should be done.
  • Make Sure that Nails for Wire Mesh should not damage the Buried PVC Conduit.

A

6.Surface Conducting:.                                                           

  • Take the approved Drawings of Electrical conduit Shop Drawing with section details, MEP coordination drawing with section details and Architectural Drawings.
  • Ensure that the civil people have finished block wall and Plastering with adequate curing and clearance is given to proceed for electrical works.
  • Check the required reference markings are available for FFL (finished floor levels).
  • All required materials shall be shifted and stored under safe custody near workplace on daily basis as per planned quantity.

1 ) Marking of Conduits:

  • Site Engineer will carry out a site survey where the PVC Conduit will be installed as per approved shop drawings.
  • Mark the exact position of the conduit route with the blue marker string and then install conduit saddles.
  • All runs must be installed as a complete system before any conductors are pulled into them. In other words, a run of conduit (to include conduit, fittings, and supports) must be complete before the conductors are installed.
  • A run of conduit should be as straight and direct as possible. When a number of conduit runs are to be installed parallel and next to each other, install them all at the same time.

2) Installation of Conduits:

(A) PVC Conduit and Accessories:

  • Conduits shall run vertically or horizontally only for surfaced run conduits.
  • Install the correct Type and size of the conduits as per approved Specification and drawing.
  • Conduit pipes shall be fixed by heavy gauge saddles, secured to suitable wood plugs or other approved plugs with screws in an approved manner at an interval of not more than 1 meter but on either side of the couplers or bends or similar fittings, saddles shall be fixed at a distance of 30cm from the center of such fittings.
  • The saddles should not be less than 19MM (width) of 24 gauge for conduits up to 25 mm dia and not less than 25mm (width) of 20 gauge for larger diameter conduits.
  • Where conduit pipes are to be laid along the trusses, steel joint etc. the same shall be secured by means of special clamps made of MS. Where as it is not possible to drill holes in the trusses members suitable clamps with bolts and nuts shall be used.

B

  • Where conduit pipes are to be laid above false ceiling, either conduit pipes shall be clamp to false ceiling frame work or suspended with suitable supports from the ceiling slab.
  • For conduit pipe run along with wall, the conduit pipe shall be clamped to wall above false ceiling in uniform pattern with special clamps if required to be approved by the Engineer-In-Charge at site.
  • Check to ensure no sharp edges within the conduit joints for surfaced conduit and to ensure proper bonding for all conduit joint for concealed PVC conduit by foreman / skill worker / sub-contractor.
  • All joints in PVC conduits, other than screwed joints, shall be cemented with a waterproof adhesive. This adhesive shall be as recommended by the conduit manufacturer.
  • All saddles, tubes and boxes must be in perfect alignment to avoid any appearance of warping when the installation is complete. Saddles should not be so tight as to prevent expansion of the conduit.
  • Power conduit and LV conduit need to be separate. Power, Lighting Circuit should be run in separate conduit than LV circuit (Data wire, Telephone wire, TV wire) conduit.
  • Conduits shall not be run closer than 15m to any steam or hot water pipes and shall be run underneath such pipes rather than over them.
  • Conduits should not also be run closer than 05m to any telephone, bell or other signaling circuit.
  • Particular care shall be taken to ensure that no grout or other foreign materials enters the conduit system through joints, or through surface openings.
  • All conduits shall be run as far as possible along the walls and ceiling and above false ceilings so as to be easily accessible for inspection if need be. While the Architects drawings indicate the distribution for light and power points
  • PVC conduits shall be ISI grade and it shall be rigid type.  Where conduits are laid in straight run, draw boxes shall be provided at intervals not exceeding 10 meters.  Between two consecutive draw boxes the right angle bends shall not exceed two in number.
  • Drawn-in boxes must be provided to give access to all conduit for the drawing-in or out of any cable after the installation is completed.
  • Terminations of PVC conduits into switch boxes, DBs, etc. shall be with adapters.  PVC conduits shall be fixed to accessories such as coupler, circular boxes, etc. with vinyl cement.

(B) GI / Steel Conduit and Accessories:

  • GI Conduiting layout complete with MEP coordination and Architectural Drawing complete with section details.
  • Check the route of GI Conduiting free from debris and no obstruction of any other activity.
  • Arrange scaffolding of sufficient height approved by HSE officer.
  • Mark the reference points on wall/ column as per civil architectural drawing.
  • Identify the circuit start point and end & mark GI Conduiting route as per approved drawings.
  • Prior to erection, all burrs and sharp edges shall be removed from the conduit together with any dirt, oil or paint which may be present.
  • Standard length of conduits shall be cut to the required length.
  • For GI Conduits threading shall be done using a threading tools and appropriate die-set. Thread will be kept to a minimum from coupling and boxes. Zink rich paint to be applied to the exposed thread part of GI conduit.
  • Where required conduits shall be bent to the required radius using manual bending machines.
  • Conduits are fixed to the building fabric by means of distance saddle with appropriate metal screws will be allowed.
  • Spacer bar are fixed in regular interval not exceeding 1000mm and the distance from either side of ay box or bend to the nearest spacer bar shall not be more than 150mm.
  • All terminal boxes area marked on the appropriate location (wall/ceiling) as per approved shop drawing and fixed with metal screws and plug. Suitable bushes are used where conduit enters the boxes to avoid any damage to the wires.
  • Wherever necessary ropes shall be pulled into conduit runs ending and kept at pull boxes for the future purpose. Ensure that sufficient number of pull boxes is installed.
  • Metallic conduit boxes shall be sued throughout metallic conduit raceway system.
  • GI flexible conduits shall be used to make connections from un-accessible location and end connections to terminal boxes.
  • All pull boxes, junction boxes fixed on the wall in the route of steel conduit shall be provided with GI cover after pulling the wires.
  • Steel conduiting shall be conforming to relevant IS specifications (IS 9537). All steel conduits shall be of heavy gauge, welded and threaded type.  Conduit accessories such as boxes, bends, inspection bends, boxes, elbows, reducers, etc. shall conform to relevant standards.  As far as possible, boxes shall have internally tapped spouts to receive the conduits.
  • Where conduits are installed in straight run, draw boxes shall be provided at intervals not exceeding 30 feet (9 meters). Between two consecutive draw boxes, the right angle bends shall not exceed two in number. Conduits shall be properly threaded and screwed in to the accessories.
  • The minimum size of conduits used shall be 20 mm. The minimum thickness of the conduits shall be 16 SWG.
  • Wherever steel conduits terminate into points control boxes, distribution boards, etc. conduits shall be rigidly connected to the boxes, boards, etc. with check nuts on either side of the entry to ensure electrical continuity and with PVC or Bakelite bushes. Turning joints in conduits wherever necessary shall be rigidly held in aligned position by check nut tightened on the running side.
  • After conduits, junction boxes, outlets, etc. are fixed in position, their outlets shall be properly plugged with PVC stop cover or with any other suitable material so that water, mortar, vermin or any other foreign material do not enter into the conduit system.
Maximum number of PVC insulated 650/1100 V Copper conductor cable conforming to IS: 694-1990
Conduit size 20mm 25mm 32mm 40mm 50mm
Wire Size (Sq.mm) S B S B S B S B S B
1.5 Sq.mm 7 5 12 10 20 14
2.5 Sq.mm 6 5 10 8 18 12
4 Sq.mm 4 3 7 6 12 10
5 Sq.mm 3 2 6 5 10 8
10 Sq.mm 2 4 3 6 5 8 6
16 Sq.mm 2 4 3 7 6
25 Sq.mm 3 2 5 4 8 6
The columns heads ‘S’ apply to runs of conduits which have distance not exceeding 4.25 m between draw in boxes and which do not deflect from the straight by an angle of more than 15 degrees.
 The columns heads ‘B’ apply to runs of conduit which deflect from the straight by an angle of more than 15 degrees.

Bending of Conduit:

  • It may be necessary to create bends in the field by heating and deforming rigid conduit.
  • For heating the rigid conduit, use a heat gun or some other flameless heat source. Do not use an open flame to heat the conduit. The rigid conduit must be heated to approximately 125˚C in order to bend without kinking.
  • Heat a length of conduit equal to approximately 10 times the rigid conduit nominal diameter.
  • Once the rigid conduit has been adequately heated, bend it to the required angle plus 3 extra degrees. The additional angle will accommodate the “spring back” which will occur during cooling.
  • After bending of the conduit is completed, immediately cool the bend using water or cold air.
Conduit Bending Radius
Size of Conduit Radius to Center of  Conduit
12  mm 100 mm
20 mm 112 mm
25 mm 144.8 mm
30 mm 183.9 mm
40mm 208 mm
50 mm 238 mm
63 mm 266 mm
75 mm 330 mm
88 mm 370 mm
100 mm 403 mm
127 mm 609 mm
152 mm 762 mm

REFERENCES:.

  • IS 3854 1966: Switches for domestic and similar purpose.
  • IS 1293 1967: Three pin plug and socket outlets.
  • IS 4614 1968: Switch Socket outlet (non-interlocking type)
  • IS 6538 1971: Three pin plugs made of resistant materials.
  • IS 9537-3 (1983): Rigid plain conduits of insulating materials.
  • IS 3419 (1989): Fittings rigid non-metallic  conduits

Method for Installation of Conceal & Surface Conduits (Part-1)


(A) Purpose: .

  • This method explains the sequence of activity for safely installation of PVC / GI Conduits and it’s accessories in the concrete slabs / columns, in block works and on Surface as per the standard Practice and Code.

(B) Storage & Material Handling:.

  • The storage area must be free from dust and Water leakages / seepages.
  • Manufacturer recommendation shall always be followed in loading/unloading and storing of Material.
  • Material and its accessories shall be unloaded handle with care in designated area of the Store (Do not directly drop to Ground) to avoid any damages.
  • Materials shall be stored in a dry place which is free from water or from weather effects and protection should be given to the material by means of covering the material with Tarpaulin sheet.
  • The Material will be stacked / unload in the site store on a proper stand on wooden loft on a flat surface at a sufficient height from Ground.
  • If Material are dispatch in packs or pallets, each pack or pallet shall be lifted individually with suitable lifting equipment.
  • The material shall be transported / Shifted in their original packing to Site location.
  • The Material should be visually inspected for damage, which may have occurred during transport.
  • If the Material is found defective it shall not be installed and the cable shall be returned to the supplier for replacement.

(C) Inspection of Materials:.

  • Check The Material according to its Type, Size, Make
  • Visual inspection:
  • Type and Make of Conduit and Accessories Material
  • Length , Width and thickness of PVC / GI / MS Conduit Material and Accessories
  • Physical Damages Inspection:
  • Damage on Material and it’s Accessories
  • In case of any damages observed during inspection, the concern report will be issued and Material shall be returned to the supplier for replacement.

(D) Concealed Conduit in Slab / Column:.

  1. Shifting Material to Working Area:

  • PVC Conduit and its accessories shall be carefully unloaded or shifted to the site by using Crane/Hydra or by sufficient manpower and moved to a defined installation location.
  • Remove the packing and ensure that the material is free from transportation damages
  • Check and ensure that approved drawings, the correct size and type of Conduit & its accessories are ready for installation.
  • Ensure that Conduit and its accessories received from site store for the installation are free of rusty parts and damages.
  1. Marking Electrical Point / Wall Conduit Drop on Slab:

  • Ensure that the civil activities are finished I,e Slab Shuttering Work and Steel Work and Site is ready for Electrical Work on Slab.
  • After completing the first layer of steel, start marking of Ceiling Points and Wall Drop Points on Slab as per approved Site Drawings.
  • Mark first the wall location for lower floor in slab as per latest Architecture layout so that it will be easy to locate the drops for switch, Wall Light Points and any other drops required for electrical system.
  • Mark the opening size in Slab or in Beam i.e window, door and shaft as per approved electrical drawing to avoid passing wall conduit drop on that area.
  • Mark the Electrical points on the slab, Wall Conduit Drop in Beam as per approved Electrical Shop Drawing.
  • Make sure that marking of Wall conduit drop is placed in center of wall, it is not out from wall or not move to any face of wall.
  • For initially use marker / Chalk for making location of electrical point on slab and wall drop after that apply oil paint on that location before conducting work so after de shuttering ,the JB or conduit drop is easily visible on slab or on beam.
  1. Installation of Junction Box and Conduit:

  • Chalk will be used to mark the PVC conduit route. Make sure that size of conduit is as per approved Electrical Shop Drawing.
  • Ceiling Conduits shall be laid on the prepared shuttering work of the ceiling slab before concrete is poured. The conduits, boxes, accessories, joints, etc. shall be laid along with the conduits.
  • Use Deep Junction Box for surface mounted lighting Fixtures and for Cable Pulling.
  • Use long radius bend or make as per site requirement by using PVC Conduit bending spring.
  • Joints between PVC conduit + fittings shall be made with suitable adhesive.
  • Try to avoid the overlapping of conduits and keep some distance between the conduits for low current and power/Lights.
  • To maintain at least 20mm spacing gap between PVC conduits running in parallel. To allow adequate / sufficient space between formwork and conduit so that embedded conduit is fully covered by concrete and will not result in any honeycomb or structural defects in the future.
  • Concealed conduits in slabs shall be brought out as vertical drops in beams, wherever such drops are required.  All vertical conduits in beams shall be left protecting from the bottom of the beam. All such ends of conduits protecting from bottom of beams shall be provided with couplings to receive extension.
  1. Fixing of Conduit & Accessories:

  • The conduits shall be adequately fixed to prevent excessive movement and damage during the pouring and setting of concrete and shall be protected from mechanical damage.
  • For Double layer of rebar, PVC conduits shall be secured to the bottom of Top layer rebar and for Single Layer rebar, PVC Conduit should be secure at top of rebar with binding Steel Wire.
  • After completing the work, tight the conduits with binding wire .PVC Conduit should be bound at intervals of not more than 1 meters by binding short lengths of steel wire, of not less than 2mm diameter twisted around the conduit and reinforcing steel. Additional Steel bonding Wire also provide near each PVC Conduit Coupler, PVC Bends and near Junction Box
  • Check there is no damage in PVC Conduit and it’s accessories before concrete is poured.
  • The open ends of Conduit should be protected during concreting by caps or plugs to prevent the ingress of building material.
  • All Junction Box, Fan Box should be protected during concreting by filling thermo coal Sheets to prevent the ingress of building material.
  • Ensure conduits are not concealed until works has been inspected and approved.
  • Before the concrete pouring the PVC conduit installation to be inspected and approved by consultant/client/contractor.
  • During concrete pouring, keep electricians for taking care of conduit to avoid any damage by others or dislocation of joints.

(E) Recess / Concealed Conducting in Wall.

  • Ensure that bricks / Block masonry work is complete and Site is given for electrical works.
  • Check the required reference markings are available for FFL (finished floor levels).
  • All required materials shall be shifted and stored under safe custody near workplace on daily basis as per planned quantity.
  • In the case of building under construction, conduit shall be buried in the wall before plastering and shall be finished neatly after erection of conduit.
  • In case of exposed brick/rubble masonry work, special care shall be taken to fix the conduit and accessories in position along with the building work.
  1. Marking of Switch Box and Light Points:

  • Mark the location of switch/socket and conduit route on proper height based on approved shop drawing.
  • No conduit smaller than 20mm in diameter or larger than 32mm diameter shall be used.
  • Mark the location of Switch Box, DB, and Junction Box for Light Point on the wall from FFL.
  1. Wall Chasing:

  • After marking of conduit and Switch Box location, Wall chasing shall be done using wall cutting machine.
  • Hammer and chisel will be used on the chased portion to get uniform depth of 50 mm or as per standard specifications.
  • All chases, grooves shall be neatly made to proper dimensions to accommodate the required number and size of conduits and staples. The outlet boxes, point control boxes, inspection and draw boxes shall be fixed as an when conduit is being laid. The recessing of conduits in walls shall be so arranged as to allow at least 12 mm plaster over the same. 
  • The chase in the wall shall be neatly made and of ample dimensions to permit the conduit to be fixed in the manner desired.
  • Wherever the length of conduit run is more than 10 meters, then circular junction box shall be provided to permit periodical inspection and of facilitate replacement of wires, if necessary. These shall be mounted flush with the wall.
  • In place where the conduit is crossing at different ceiling height, uniform bending shall be done. The bending of conduit shall be done using proper bending springs.
  • Conduits will be cleaned with a round file from inside and outside of the pipe after cutting.
  • Connect the conduit by using PVC solvent with an adaptor to the junction box. Apply PVC Solvent cement on the portion of conduit entering into coupler wherever applicable.
  • PVC Conduits shall be duly fixed by using a hook or Nail. Distance of GI hook / Nail shall be maintained at 500 mm at intervals.
  • Embedded back box, JB shall be protected by covering with brown tape filled with jute/gunny bag.
  1. Installation of the Box / Enclosure:

  • At Planning and Designing Level, always Select DB Wall block work thickness should be 200 mm instead of 100 mm for easy DB installation.
  • For Properly Installation of DB and Switch Box, locate plaster level points near DB or Switch Board.
  • The mounted height of the Switch Board is generally 1200mm (Bottom of Switch Box) in all rooms ,300 mm near Bed and for DB it is generally 1800mm (bottom of panel) or as per approved Drawings.
  • Ensure the box size and accordingly cut a bit larger size of box in marked place of block wall with sufficient depth.
  • Fix the GI Metal box of appropriate size and level with the help of spirit level.
  • Installed the Switch Box and DB with the use of cement mortar around the box. Make sure that it is flush with finished plaster level.

s

  • The bottom portion of box should match the marked level as per consultant approved height for switch/ socket and/or as per local applicable wiring regulation requirements.
  • Apply cement filler to fix the box properly and leave for setting, insert the required lengths of conduits on their paths and don’t connect with boxes until next day.
  • Next day, after setting of box connect the dropped conduits for switch/socket to the box.
  • The switch box shall be flush with the plaster. The height of the switch boxes shall be as indicated in the drawings. The switch boxes should be sufficient depth to give minimum 20 mm plaster cover to conduits embedded.
  • Distribution board interiors will not be installed in cabinets until all conduits connections to the cabinet have been completed.
  • Trim for flush mounted cabinets will be installed in plaster frame, flushed with furnished wall.
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