2. Contents
• Introduction, Electrical Schedule, Catalogues
• Market Survey and source selection, Recording of estimates,
Determination of required quantity of material, Labor conditions
• Determination of cost material and labour, Contingencies,
Overhead charges, Profit, Purchase system, Purchase enquiry and
selection of appropriate purchase mode, Comparative statement,
Purchase orders
• Payment of bills, Tender form, General idea about IE rule, Indian
Electricity Act and major applicable I.E rules.
3. Introduction
Estimating is an art of assessment of quantities of different
items and cost thereof to plan the amount required for
executing a work before carrying out the actual work. The
person preparing the estimate is known as an estimator.
The functions of estimator
• Estimation of quantities of the material required and cost
involved.
• Analysis of costs.
• Maintaining proper records.
• Providing assistance.
4. • Estimating is essential as it provides us an accurate evaluation
of the amount of money required, availability of material etc. In
case any program/contract is taken in hand and started without
estimating, it will be difficult, rather impossible to complete the
work uninterruptedly because shortage of money or non-
availability of materials.
• Estimating is a process used by electricians, construction
managers and engineers to determine the amount and cost of
electricity required for a specific process. There are two general
methods of creating accurate electrical estimates: computer
software and manual calculations.
5. 1. Estimate give an idea of the cost of the work and hence its
feasibility can be determined i,e whether the project could be
taken up with in the funds available or not.
2. Estimate gives an idea of time required for the completion of
the work.
3. Estimate is required to invite the tenders and Quotations and to
arrange contract.
4. Estimate is also required to control the expenditure during the
execution of work.
5. Estimate decides whether the proposed plan matches the funds
available or not.
NEED FOR ESTIMATION AND COSTING
6. Facts should be known to an Estimator
While estimator preparing an estimate for internal wiring,
• Complete specifications of the materials used for
installation.
• Complete schedule of the points to be wired with their
switches and fittings.
• Position of main switch board and distribution board.
• Time to complete the job/work.
7. Electrical Schedule
• The electrical load schedule is an estimate of the instantaneous
electrical loads operating in a facility, in terms of active,
reactive and apparent power (measured in kW, kVAR and kVA
respectively). The load schedule is usually categorised by
switchboard.
• An electrical schedule is that list or plan of building which
provides us the information regarding the number of points
(ceiling outlets. Bracket outlets, switches, wall plugs and other
special plugs) in each of a building under estimation.
8. Catalogues
• The main objective of a catalogue is to promote the products and
services offered by the company. A catalogue layout properly
designed must show your company's products or services
arranged neatly, so that they can be easily recognized; and, at the
same time, it must look attractive to improve your sales.
• For the pricing of the estimate up-to-date catalogues, quotations
from manufactures and wholesale dealers for the special
materials must be available with the estimator.
• The estimator saves the time by making judicious selection of
standard catalogues, which are most useful for his work.
9. Market Survey and source selection
Good estimating is possible only with an update knowledge of
• Availability of products
• Sources for production, vendor selection
• New products and their quality
• Prices of products, discounts etc.
The market survey for collection of the above information and
retention of the same in a library helps in easier estimation, and
decision making for selection of materials and vendors.
10. It is important to conduct a market survey of the availability of
products and also to obtain approvals of approved
suppliers/vendors to avoid poor quality of products being used at
any stage. For reference the estimator should preferably
• Retain a list of approved suppliers/vendors both in alphabetical
order and also product wise,
• Retain a list of approved standard products
11. In order to make a survey easily accessible categorisation/
classification of products can be made in a format as given below:
12. Recording of Estimates
•All the estimates must be written in a book. It is preferable to write
estimates on loose sheets in order to file them with the contract papers.
•The most convenient ruling for estimate book is shown below, Each
estimate should be headed with a sufficient description, giving the date
of submission and name of the estimator.
13. Determination of Required Quantity of Material
• The determination of quantity of casing-capping, wire for house wring is
very tedious job.
• The first step is to decide the layout to be adopted, because this will
obviously affect the measurements.
• Determining casing-capping and wire or cable for the decided layout is to
start at supply cutouts or leads taken out from the meter to be connected to
the consumer main board, writing down the size and length with full
description of casing-capping and cables.
• Now prepare a list of switches, switch boxes, pendants, sockets and other
items. This list may be prepared exactly as all these items will be
mentioned n the schedule.
• The only variable items are flexible cords, but an allowance of 0.6 meter
per pendant is sufficiently accurate.
• A small amount is added to cover the cost of screws, plugs and other minor
requirements.
14. Determination of cost material,
labour condition
• The next and most difficult item to estimate is labour, and there are several
factors in the construction of building which affects it. This is where the
experience is required and the helpful use of data collected from other jobs.
• Best way to determine the cost of material required for wiring is to prepare a
table with the columns, discussed in recording of estimates, insert the items
with complete specifications and quantity required in their respective
columns.
• Then the rates for all items from standard catalogues, the total cost item
wise, and finally the totaling. If the any special items requires then quotation
has to be asked from the manufacturer, thus we will reach the total cost of
the material required.
15. To determine the labour cost one of the following methods must
be adopted.
• Determine the total number of points, taking two points for
main board and one point for each sub-circuit in addition to the
number of points to be installed. Then find out the total labour
cost charging @65Rs., 105, 125 per point for cleat, casing –
capping, wiring respectively.
• Provide the labour charges as 15%, 20% or 25% of material
cost.
• Determine the labour required from the table below and then
estimate the total labour cost with the help of labour wages
given in table below,
17. Contingencies
• This is for damaged and unforeseen items. The amount is
provided under the head of contingencies to cover the
unforeseen expenditure such as to cover extra costs on amount
of devices in delivery, minor accidents and other variations
from the plans of estimating department.
• It is usually expressed as a percentage of total
cost(material+labour cost ) say 5%.
• The contingencies fully compensate additional material cost,
labour cost and other damage expenses which could not be
accounted for. Such expenses may be due to natural calamities
such as Floods, Earthquakes, hailstorms etc.
18. Overhead charges
• The overhead charges cover all expenditure necessary to carry
out the business, in addition to the special expenditure,
incurred in carrying out a particular job. Such as rent of offices
and workshop, allowance for the wear and tear of buildings,
wages of clerical staff, taxes, lightening, advertising,
insurance, telephone, and other travel expenses. Since these
cannot be charged against any one contract, however these
costs are large then to arrive at the true cost of the job, a
definite 10 to 15% is added to the net cost of each estimate.
19. Profit
This is usually added in the form of percentage to the gross/true
cost of the job. This amount is purely depending on the contactor,
and his decision usually governed by the following factors:
• Size of the job with him
• Degree of competition
• The state of turnover and
• His anxiety to secure a particular job
20. Purchase system
Divided in to 3 major heads,
Objectives:
• To purchase completely and wisely authorized equipments as
per desired specifications
• Ensure that fair and open purchase practices are followed
• Ensure timely formulation and commitment of purchase
budget requirements
• Ensure the investment made should be at optimum level
21. Functions:
• Creation of continuously updated lists of selected reliable
vendors
• Maintenance of vendor records I,e given as below
• Analyzing offers for decision making by the technical authority
• Issue of purchase orders in time
• Obtaining govt clearance
• Maintaining library of product catalogues, price lists
25. Evaluation of tender
• The offer was received in time
• Basic price of the quantities for which it is valid.
• Taxes that are payable
• Terms of delivery
• Acceptance of penalty for late delivery
• Specifications offered are the same as demanded
• Validity period is adequate
26. Purchase orders
All purchase orders shall carry the following information
1. Purchase order number and date
2. Detailed specifications of the items as quoted by the tenderer
3. Value of the purchase order
4. Name of the supplier
5. Due date of delivery
6. Quantity of items ordered
7. Taxes if any to be specified in the order
8. Mode of payment, advance, discount etc.
27. Payment of Bills
• In order to maintain credibility it is very much important that
the bills of suppliers/vendors are paid in an agreed time.
Tender form
By tender is meant a form on which an offer is made from a
party to make supply or undertake some work at its specified
rates.
28. Indian Electricity Rules(1956)
Indian electricity rules have been framed to ensure safety, satisfactory
operation of equipment to avoid fire risk.
Rule 28: Voltage
Potential difference between the any two conductors is called as
voltage and that can be measured by means of voltmeter.
• Low voltage : Does not exceed 250v under normal condition
• Medium voltage : Does not exceed 650v under normal condition
• High voltage : Does not exceed 33kv under normal condition
• Extra High voltage : voltage exceed 33kv
29. Rule 29: Construction, installation, protection,
operation and maintenance of electric supply
lines and apparatus
• All electric supply lines and apparatus should be capable
of carry the sufficient power and should also have
sufficient mechanical strength.
• Followed the standards of the INDIAN STANDARDS
INSTITUTIONS(ISI) so as to prevent danger.
30. Rule 30: Service Lines and apparatus on consumer premises.
1. The supplier shall ensure that all electric supply lines, wires, fittings and
apparatus belonging to him or under his control, which are on a consumer's
premises are in safe condition.
2. Service lines placed by the supplier on the premises of a consumer which are
underground or which are accessible shall be so insulated and protected by the
supplier as to be secured under all ordinary conditions against electrical,
mechanical, chemical or other injury to the insulation.
3. The consumer shall take precautions for the safe custody of the equipment on
his premises belonging to the supplier.
4. The consumer shall also ensure that the installation under his control is
maintained in a safe condition.
31. Rule 46: Periodical inspections and testing of consumer’s
installation:
• Where an installation is already connected to the supply system of the
supplier, every such installation shall be periodically inspected and tested at
intervals not exceeding five years either by the Inspector [under the control of
the Central Government
• The fees for such inspection and test shall be determined by the Central or the
State Government.
• Customer give surety to the supplier for good maintenance
32. Rule 47: Testing of consumer’s installation.
• Upon receipt of an application for a new or additional supply of
energy and before connecting the supply or reconnecting the
same after a period of six months, the supplier shall inspect and
test the applicant's installation.
• If as a result of such inspection and test, the supplier is satisfied
that the installation is likely to constitute danger, he shall serve
on the applicant a notice in writing requiring him to make such
modifications as are necessary to render the installation safe.
33. Rule 50: Supply to consumers
The supplier shall not continue to give supply to consumer unless
• A suitable linked switch or a CB of required capacity to carry
and break the current, is placed near to MDB.( Near to the
commencement of supply)
• Every individual circuit is protected against excess energy by
means of suitable CB.
• Adequate precautions are taken to ensure that no live parts are
exposed.
34. Rule 54. Declared voltage of supply to consumer:
• Declared voltage at the supply point by more than 5% in the
case of low or medium voltage, or by more than 12.5 per cent
in the case of high or extra high voltages.
Rule 55. Declared frequency of supply to consumer:
• The frequency of an alternating current supply should not
vary from the declared frequency by more than 3 per cent.
35. Rule 77: Clearance above ground of the lowest conductor:
• The conductor of an overhead line, including service lines,
erected across a street shall not be at a height less than
a. For low and medium voltage lines : 5.8 meters(19ft)
b. For high voltage lines : 6.1 meters(20ft)
• The conductor of an overhead line, including service lines,
erected along a street shall not be at a height less than
a. For low and medium voltage lines : 5.5 meters(18ft)
b. For high voltage lines : 5.8 meters(19ft)
36. Rule 79: Clearance from buildings of low and
medium voltage lines and service lines.
Where a low or medium voltage overhead lines passes above or
adjacent to or terminates on any building,
For any flat roof, open balcony, verandah roof:-
• When the line passes above the building, a vertical clearance of
2.44m(8ft) from the highest point.
• When the line passes adjacent to the building, a horizontal clearance
of 1.22m(4ft) from the nearest point
For pitched roof:-
• Above building, a vertical clearance of 2.44m(8ft) immediately
under the lines.
• Adjacent to the building, a horizontal clearance of 1.22m(4ft)
