Estimation & Costing : Estimation of Lighting Schemes

INTRODUCTION TO ESTIMATION AND COSTING:

Electrical estimating is a process used by electricians, construction managers and engineers to determine the amount and cost of electricity required for a specific location or process. There are two general methods of creating accurate electrical. Estimations of computer software or manual calculations both methods have value, benefits and risks. Original electrical estimating software options were quite clumsy to use, but recent enhancements have vastly improved this tool for electrical estimation.

Electrical estimating computer software has increased in popularity as it has improved in quality and performance. This tool is designed for use by electricians, architects and electrical engineers. There are different versions available for residential, commercial or prototype development. An estimating technique is an approach to predicting cost or revenue. Using a consistent methodology is important to achieve reliable and comparable results.

Firms may have specific policies their personnel have to follow when making estimates to ensure that the approach will be similar no matter who prepares the estimate. This can help reduce problems associated with variances in methodology, like an offer from one mechanic in a shop of a very low price for service while another indicates the cost of a job will be much higher. When preparing estimates, people can broadly divide them into detailed and approximate types. Approximate estimates offer a rough guess of the cost, based on similar projects, experience, and quick research.

They can be helpful for getting a general idea of expenses before proceeding with a more detailed estimate. For people soliciting estimates, they can't be quoted as firm bids, but may provide a frame of reference. A homeowner looking for a new roof, for example, could ask for an approximate estimate from several contractors to learn more about the range of possible prices. Importance of Quality Cost Estimates The reliability of project cost estimates at every stage in the project development process is necessary for responsible fiscal management. Unreliable cost estimates result in severe problems in programming, budgeting, and planning.

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 categorized by switchboard or occasionally by sub- facility / area.

CATALOGUES:

• The main objective of a catalogue is to promote the products and services offered by your 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. In addition, the catalogue layout must be strategically arranged in order to give more importance to certain items or to make the catalogue look more eye catching.
  
  
• Finally, the visual coherence on which a company's corporate Image is supported must be kept. A catalogue may promote products within promotional packages or lithe known products.
  
  

It may inform the audience about the new comfort and convenience of a service or it can simply contain small businesses' month offers.

TYPES OF ELECTRIC LAMPS

Ø Arc lamps

Ø Incandescent lamps

Ø Gas-filled lamps

Ø Gaseous Discharge lamps

TYPES OF LIGHTING SCHEMES:

Ø Direct

Ø Semi-direct

Ø Indirect

Ø General lighting schemes

REQUIREMENTS OF LIGHTING SCHEMES:

The lighting scheme should provide

Ø Adequate illumination

Ø Light of suitable color

Ø Light distribution all over the working plane as uniform as possible

Ø Avoid glare and hard shadows as far possible.

DESIGNING OF LIGHTING SCHEMES:

In the designing of lighting schemes following factors are considered.

Ø Illumination level

Ø Uniformity of illumination

Ø Color of light

Ø Shadows

Ø Glare

Ø Mounting height

Ø Spacing of luminaires and

Ø Color of surrounding walls.

METHODS OF LIGHTING CALCULATIONS:

Ø Watts per square meter method

This is a “rule of thumb” method. It is very handy for rough calculations or checking. It consists of making an allowance of watts/m² of area to be illuminated according to the illumination desired on the assumption of an average figure of overall efficiency of the system.

Ø Lumen or light flux method

This method is applicable to those cases where the sources of light are such as to produce an approximate uniform illumination over the working plane or where an average value is required. Lumens received on the working plane may be determined from the relation

Ø Point-to-point or inverse square law method.

This is applicable where the illumination at a point due to one or more source of light is required, the candle power of the sources in the direction under consideration being known. This method is not commonly used because of its complicated and cumbersome applications

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