Electrical installation symbols

These are scale drawings based upon the architect s site plan of the building and show the position of the electrical equipment which is to be installed. The electrical equipment is identified by a graphical symbol. The standard symbols used by the electrical contracting industry are those recommended by the British Standard EN 60617, Graphical Symbols for Electrical Power, Telecommunications and Electronic Diagrams. Some of the more common electrical installation symbols are given in Fig. 3.83. 

The British Standard BS EN 60617 recommends that particular graphical symbols be used to represent a range of electronic components on circuit diagrams. The same British Standard recommends a range of symbols suitable for electrical installation circuits with which electricians will already be familiar. Figure 3.69 shows a selection of electronic symbols. 

The unit of capacitance is the farad (symbol F), to commemorate the name of the English scientist Michael Faraday. However, for practical purposes the farad is much too large, and in electrical installation work and electronics we use fractions of a farad as follows ... 

The harmonisation process has been managed by the Committee of Electrotechnical Standardisation (CENELEC) in Europe. The committee standardises many subjects of electrical and electronic engineering, not only those pertaining to hazardous area equipment and its installation. When eqnipment is certified in accordance with a CENELEC standard the symbol Ex is modified to become EEx . This serves to give the designer and the user extra confidence in the certification. 

The electrical equipment will be identified by graphical symbols on the plan, as described in Chapter 5 and shown in Fig. 5.5. The drawing will be to scale, and if we say the scale was 1 100, then 10 mm or 1cm on the site plan will represent 1 m in the building. The electrician can take measurements from the drawing and transfer these to the building, probably using a retractable steel rule. They can then mark on the walls of the building with a piece of chalk or a marker the final positions of the electrical equipment which is to be installed. 

Here, yi, yu, and ym denote the decisions to install technology I, II, or III, respectively. Symbol D denotes the electricity demand, and Pi, Pn, and Pm denote the power supplied by each technology. For simplicity we assume that Pi = Pn = Pm = 10, and we set D — 10. Note that the demand constraint [7.9e] implies that only one technology must be installed. AH the objectives (C, E, L) are normalized by their best and worst possible values (these can be obtained from Table 7.1) so as to lie in the range [0,1]. 

Part 5, Section 5.1 1982 Halon 1301 total flooding systems BS 5345 Code of Practice for the selection, installation and maintenance of electrical apparatus for use in potentially explosive atmospheres Part 1 1976 Basic requirements for all parts of the code BS 5423 1987 Specification for portable fire extinguishers BS 5499 Fire safety signs, notices and graphic symbols Part 1 1984 Specification for fire safety signs BS 5839 Fire detection and alarm systems in buildings Part 1 1980 Code of Practice for installation and servicing BS 5908 1980 Code of Practice for fire precautions in chemical plant... 

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