Points To Be Considered While Preparing The Estimate

Points To Be Considered While Preparing The Estimate of Electrical Wiring Points : points to be considered while preparing the estimate, building wiring estimating & costing, estimate the installation of an electrical distribution, electrical design and estimation Points To Be Considered While Preparing the Estimate

1. Length of conduit required can be calculated by going through the plan of the building.
2. Allow 10% of total length for wastage in any system.
3. To calculate the length of wire, take the length of conduit after allowing wastage.
4. The length of wire can be taken as 2.5 times the length of conduit for looping system and 2 times for junction box system.
5. The length of the looping wire etc. in switch boxes shall not be lesser than 0.5. times of the height of the box itself.
6. The length of wire to be provided form the main board for connection to meter board shall not be more than 7.5 meters and should be one size higher than the actual size selected for wiring.
7. The clearance provided between ceiling and the running installation the wall normally is taken as 0.25 to 0.5 meters. However this should be judged only by the type of building, beams crossing etc. Appearance should also be given due consideration.
8. All the controlling switches in power wiring shall be mounted on the metal frame of suitable design.
9. All the sub-circuits must have its own continuous earth wire.
10. The wiring of power and light must be separated from each other, from the commencement of supply itself and shall not be run on the same conduits.
11. There is no necessity of providing separate earth for the lighting loads by the consumer; supplier’s earth shall be sufficient.
12. All the wall plugs must be of three pins and should be earthed.
13. More than one circuit, wires should not be dropped down in one switch box. Separate boxes must be provided for each circuits.
14. Labor can be calculated by calculating man days and multiplying by the charges / day.
15. For material handling, (i.e., transporting charges of materials to the site) will usually be judged by route length and available cargo movers. Any how it should not be more than 5% (max.) of material cost.
16. Over head charges will generally be assumed as 10% to 15% of the total cost.
17. In large installations, tool charges are to be included. It is usually 3 to 5% of the total cost.
18. Strictly follow I.E. Rules of 1956. ISI specifications, National Electric Code and the requirements of State Electricity Board Inspectors.
19. Wiring of All multi-stoned buildings above 15.0 M Height must be inspected by Electrical Inspector and he has to approve (Rule 50 A)
20. Any wiring system has to last for 25 years. Hence high quality materials are to be used, high quality workmanship must be executed through qualified contractors hence materials host and labour charges will be high.
21. For loads above 4 KW, 3 ph. Supply must be arranged.
22. The wiring should be done very close to the ceiling.
23. . For final sub-circuits, use 1 sq. mm of copper or 1.5 sq. mm. Al.
24. The consumer should provide ONE earth electrode for single phase supply and TWO earth electrodes for 3 phase supply. Earth pipe dimension: 40 mm dia and 2.5 M length.
25. If more than one electrode is provide, all earth electrodes must be linked, for combined kw resistance. Water them periodically.
26. Use aluminum of 14 SWG TC (Tinned Copper) for earth leads.
27. All non current carrying metallic parts must be provided with 2 separate and distinct earth wires.
28. . In bath rooms, all non electrical metal work including bath tubs, water pipes sinks must be bonded together and earthed.
29. Do not exceed per circuit 800 watts or 10 lights or fans.
30. . Do not exceed per circuit 2numbers of plug points for power circuit.
31. Use heavily insulated, flexible cables for domestic appliances.
32. Do not keep pump motors exposed to open atmosphere. Provide weather proof covers.
33. Provide lighting arresters, for High Rise Buildings. IR values must be 1 M ohm.
34. Provide Earth Leakage Circuit breakers, for loads exceeding 5 KW.
35. If Generators are used, connect them in a standard way and ensure that it is NOT paralleled with EB supply.
36. Insist upon safety precautions as per rules.