Design Considerations for Residential Houses, Multistory, Multiflat
Buildings; Office blocks, factories and Public buildings.
Some of the design considerations are outlined below. It
should be noted that the experience of the engineer is very important in
design.
Architectural and
Structural Drawings.
In most projects, the Electrical Engineer forms part of a
design team. This team include other service engineers and the Architect. Other
members of the team provide information which the engineer utilizes for his design.
The Architect and the Structural Engineer provide the Electrical Engineer with
both architectural and Structural drawings which are used by the Electrical
Engineer for Electrical Services Design Work. Some of the information provided
by these drawings include: the nature, location and intended use of the
building of interest; the location of beams and columns, and cantilevers; as
well as other details which would be of interest to the engineer and which will
influence the design subsequently.
Luminous Level and
Electrical Facilities to be installed or provided for.
A good understanding of the proposed project would enable
the Engineer determine the appropriate Electrical Facilities to be installed or
provided for within the limits of available resources. This calls for good
client consultant relationship for proper understanding of the needs of the
client as well as the recommendations of the consultant. The Luminous
requirement of the various parts of the building is also determined.
Selection of Fittings, Luminaires, Cables and other
Facilities
Calculations are
carried out to determine the appropriate fittings and cables as well as other
facilities required to meet the design specifications laid down by the Engineer.
These calculations are consistent with the principles we have studied in this
course (Electrical Services Design) up till now. The calculations are however
modified to make room for peculiarities of circumstances.
The design is carried out in such a way as to meet basic
standards and regulations guiding such work and design. When the appropriate
number of fittings has been determined, the next step in the design can then be
taken.
Load Analysis
The Load analysis is then carried out making provision for
diversity factors where appropriate. This has to be in line with regulating
standards. The result of the load analysis will determine the service cable
sizes as well as the kind of installation required in addition to protection
and control.
Protection and Control
The result of the Load Analysis is now used to determine the
kind of Protection and Control required for the proposed building. The number
and type of Distribution Boards and their current and Voltage specifications
can be determined using the results of the Load analysis. In addition to this,
the switch gears are also determined in a similar way. The control and
protection of each final sub-circuit is determined likewise. When this exercise
is concluded, the Engineer would then specify the ratings, type and number of
all protective and control devices along with the associated cables for proper
connection.
Appropriate drawings are produced at each stage of the
design.
Bill of Quantities
Electrical quantities are extracted from these drawings. (
These bills are used for tendering by contractors.) The current prices of items
and quantities are used to estimate the cost of the proposed project.
Provisions are made for fees, Labour and variations as a result of inflation
and price fluctuations. This is very important as cost is a very important
factor in Electrical Services Design.
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