CONDUIT AND ACCESSORIES USING AS PER WIRING REGULATIONS
Conduit, accessories and trunking installation should comply with the latest issued Regulations for the Electrical Equipment of Buildings by the Institution of Electrical Engineers, unless otherwise approved by the Engineer. In addition installation should also comply with all local electricity regulations.
All metallic conduit and conduit fittings should be galvanized, heavy gauge steel, screwed, solid drawn or weld type complying with IEC 423 and IEC 614.
Conduit Types and Specifications
Following conduit and raceways specification should be utilize if where it is required or as per instruction of authorized engineer:
· Power Conduit- HDPE/ASTM F2160;
· Electrical Conduit- EB, PE & rigid PVC/UL 651A/UL 651B;
· Telecommunication Conduit- HDPE/ASTM F2160;
· Premise Raceways- UL 2024 Optical Fiber Cable Raceway.
PE Conduit uses in power transmission and communication like substation to transformer, secondary transformer to end-user cable, telephone, CATV and data transmission etc. PE conduit uses mainly for its significant physical advantages over other materials like-
· Resist brightness with age or cold weather;
· Low temperature impact resistance;
· Permanent flexibility;
· Ambient temperature range -30oC to 180oC
PE Conduit Feature
01. Multiple colour and stripes are available;
02. Pre-installed or cable in conduits are available;
03.Corrugated flexible inner ducts are available;
04.Self-supporting or built-in suspension strands are available.
What Is Difference between Conduit and Pipe
In general it is very similar between plastic pipe and conduit; but in use completely different between them. So, it must be consider what it is and where it is going to use for.
o Conduit do not have long term internal pressure what have in pipe;
o Due to long term stress pipes need hydrostatic design basis where is not require in conduit;
o Internal clearance for pipe is required on flow of volume where in conduit it’s depends on cable possession, group of cable, diameter of cable, cable pulling system, length of cable etc;
o Conduit installation path in vertical, horizontal, curvature is very much important on cable nature;
o In short pulling length up to 55% and for long pulling length below 40% should be fill-up the conduit volume, but in pipe no need to keep any empty space.
Conduit Installation Factors
Mechanical Stress is an issue to select the placement the conduit. If exceed the maximum allowable pulling tension and bending radii, conduit may damage.
Pulling Tension should consider during conduit installation. Tail loading, length of conduit, bending radii should control to keep the safe pulling tension.
Bending Radii often face on conduit pulling route, pulling tension and mechanical stress increase in bending curve. It’s important to select bending radii to avoid conduit damage in curved area.
Conduit Trenching may various types, but open trench and continuous trench methods are very traditional. Also trench digging, placing conduit and backfilling is important in conduit trenching.
Conduit Jointing can be variety of thermal and mechanical methods, but for each proper engineering design and system should follow.
Cable Installation in conduit is an important job which can be accomplished in a few ways, such as-
§ Cable pulling in conduit using rope or pull line;
§ Cable pulling in conduit using specialized high volume jet of air;
§ Cable-in-Conduit or pre-installed cable in conduit by manufacturer.
Conditions for Conduit and Trunking Wiring
No conduit smaller than 19mm outside diameter should be used.
Standard circular boxes or machined face heavy-duty steel adaptable boxes with machined heavy type lids should be used throughout. For outdoor mounting all boxes should be galvanized, weatherproof and fitted with external fixing lugs.
Conduit terminations should be fitted with brass bushes.
The use of running threads, solid elbows and solid tees will not be permitted.
Conduit ends should be carefully reamed to remove burrs. Draw-in boxes should be provided at intervals not exceeding 10m in straight-through runs.
Conduit runs should be in either the vertical or horizontal direction unless otherwise approved and should be arranged to minimize accumulation of moisture. Provision for drainage should be made at the lowest points of each run.
Conduits should be supported on heavy galvanized spacer saddles so as to stand off at least 6 mm from the fixing surface.
Provision should be made for the support of internal conductors in instances where the length of the vertical run exceeds 5m.
All conduits run in any circuit are to be completed before any cables are pulled in.
Flexible metallic conduit should be used where relative movement is required between the conduit and connected apparatus, and a separate copper connection provided to maintain earth continuity.
Ensure the better service life of conduit and cable installed into conduit should follow the international and local standard and wiring regulations. The maximum number of cables in any conduit should be in accordance with the latest issue of the IEE Regulations for the Electrical Equipment of Buildings.