Estimating of Electrical Wiring

Estimating of Electrical Wiring Points : Estimating of Electrical Wiring, What Is Estimating Electrical Wiring, Steps of Form and Estimate Are, Estimating and Its Importance, Estimating of Electrical Wiring Tools, The Map Measure, Tape Measures, The Tally What Is Estimating Estimating means to determine the quantities of various items required to execute a job and to assess the cost of the execution. The estimator keeping in view the requirements arrived at during initial planning, chalk out a list of items and quantities. The cost is determined by him by consulting the price catalogue and schedule of labour rates. Steps of Form and Estimate Are (1) Chalk out a list of items and quantities required.
(2) Consult the rate catalogues for pricing the various items.
(3) Assess the exact number of workmen required to complete the job and after consulting the schedule of labour rates add the labour cost to the estimate under preparation. It should be noted that number of workmen required is dependent upon the time limit fixed to complete the service.
(4) Add supervision charges and executor’s profit.
(5) In case of Govt. Organization, where the work is to be executed the contractor, the tenders are floated only after correctly specifying the description of each item, to avoid any misunderstanding while execution. Estimating and Its Importance Estimating is one of the foundation stones of all electrical contracting businesses and consequently must be efficient and accurate to provide a good base to develop safely and keep in business. The only certain way to produce an accurate estimate is to measure the work content; price it accurately and arrive at a true estimated cost, to which will be added the overhead costs and profit element. The result should not be abandoned or adjusted because of whims of management, pressure of competition or any other temptation to cut a, price to obtain work. After all, it is the easiest job in the world to make a full order book of under-priced jobs, with the inevitable result of securing a load of ‘loss’ making jobs and eventual failure of the business.

Estimating is a costly business and should be given a great deal of attention before being entered into. The cost of an estimate in preparation can vary from 1 % to 2% of the cost of the project. A reasonable success rate can be I in 6% and consequently the real cost of estimating is as much as 12% of the jobs obtained .by estimating. With this is mind, management must decide whether or not to tender for every enquiry that comes to the office. Some enquiries for work which are well outside of the firms experience, or geographically too far away for proper control and competitive running costs should not be entertained. For example, tenders for house wiring and straight forward hospital and school contracts are always very competitive and logically can be done by local firms far more economically than firms who have to include traveling and lodging costs. Having decided to tender, the enquiry must be handed to the estimator without delay with clear instructions as to the critical date when the completed tender take off is to be available for management to decide upon the profit factor and final price bid. A lot of costly hard work including meticulous measuring and pricing can be thrown away by having to arrive at a rushed decision by management through lack of time to give the matter the careful time-consuming attention required to put in the final price. The estimator may be either a full time estimator or, more likely in small and medium size firms, an experienced engineer operative to put on paper all that is required to carry out the work. The next step is to examine the enquiry very carefully so that a good understanding of the work is achieved. To assist in this preliminary step a check list is useful. Estimating Tools The tools required to facilitate estimating are few, and considering their utility the aggregate cost is not great. The value of such tools as timesavers and aids to securing accuracy depends on the ability of the individual estimator to use them advantageously. The list shows the tools more or less confined to estimating and does not include equipment such as comptometers, adding machines, and testing equipment, which may be used along with the estimating procedure. Although adding machines, and testing equipment, which may be used along with the estimating procedure. 1. The Map Measure The map measure, commonly known in the profession as the “roto-meter”, is considered by most electrical estimators engaged in large construction work as the most valuable of tools. The map measure provides a mean of rapidly and accurately measuring feeder and branch-circuit runs. It is care should be exercised in the selection of this instruments, as there are many types of measuring instruments on the market, some of many types of measuring instruments on the market, some of which are better adapted to the work thank no manufacturer’s name.

The style of map measure busts adapted to electrical estimating very closely resembles pocket watch. It is approximately 1 —/4 in. In a diameter and 9/16 in. thick, with a rest pin on the top and a contact wheel on the bottom. On the face are three dials; One large and two small, each having an indicating hand. The large hand indicates inches and the two small hands indicate feet. One small dial is marked for 0 to 10 f and the other for 0 to 100 ft.

The contact wheel (wheel that is rolled over the line to be measured) should have small gear - like corrugations to prevent slipping. The reset stem should be of the pin type and no to long. The small pin-type stem helps to prevent accidental resting. Crystals should no breakable. New as well as used instruments should checked from time to time to sees-that there is no slippage. Indicating hand positions should also be checked. The hands may become loose or slightly shifted if the tool is dropped.

In taking measurements (when large quantities are taken off for each reading) it is not necessary to reduce the instrument readings to inches. The indicator feet can be read directly as 1nt feet. For every instrument, foot readings can be 50 plan feet for 1/4- in scale, 100 plan feet for 1/8 — in. scale, and 200 plan feet for 1/16 — in. scale. This will introduce approximately 5.per cent overrun, which will compensate for shrinkage.

For example, assume we have a 1/8 — in. Scale plan. Twelve inches on the plan represents 6 ft. It is customary to add 5 percent to allow for shrinkage. Adding 5 per cent to 96 ft gives 100.8 ft. The difference between the direct reading and the calculated feet is 0.8 per cent. If one feels that the should compensate for this 0.8 per cent, the addition may be made to the final summary.

As will be illustrated later, one of the advantages of a rotometer is that one hand is free to mark off the sections measured. If one wishes to stop and make notes it is not necessary to record the measurements since the record is on the meter. When the notes re completed the measuring can proceed. Under a latter heading, “Measuring Branch circuit conduit”, further details will be given on the use of rotometers for securing speed, and accuracy. 2. Tape Measures The tape measure is preferred to the rotometer by some estimators. There are 3/16 in steel tapes on the market which have the foot markings for direct ‘readings. The special marking is on each foot of the tape A V4 mi Scale has a “48 ft” marking at the 12-in. point, a “96 ¼- in. intervals. In the same way the 1/8 — in Scale tape has “96 ft”, “192 ft”, and similar markings at 12 — ins. intervals with intermediate markings at 1/8 — in Intervals.

One can readily appreciate the value of such a tape for measuring long runs, it is also used successfully for accumulated measurements of short runs. For such work, the tape is held between the thumb and forefinger of the right hand and drawn out by the left, The accumulated measurements are always marked by the right thumb. As each measurement is complete, the right hand is advanced to the next starting point and the tape drawn out, to the line being measured. This gives plan measurement, and the allowance for shrinkage is in added to the sum of the accumulated measurement.

Estimators who use this method of taking off quantities become very proficient and have confidence in the accuracy of their work. Unless one have confidence in the accuracy of a be careful that he does not accidentally .use the wrong side. TO avoid such difficulties, some estimators fabricate. Parking on 18 — or 24— in. strips of flexible fiber. The is only one set of markings, the danger of using the wrong scale is eliminated. 3. The Tally Any job large enough to justify the use of a Tally is likely to require considerable study as the estimating progresses. IN the majority of cases, the take-off of lighting outlets covers the project more completely than any other branch of the estimate.

As a result, it affords the best opportunity to pick up scattered plan notes and more or less obscured details. To make the most of this opportunity, the estimator used the tally to record the count so that he can stop at will to study the details or make notes.