Building Services Engineering 5th Edition Handbook

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13 Electrical installations Learning objectives Study of this chapter will enable the reader to: 1. understand how electricity is generated and distributed; 2. know the difference between single- and three-phase electricity; 3. distinguish line, neutral and earth conductors; 4. calculate the resistance of conductors; 5. understand the temperature effect of a current; 6. calculate current and power in electrical circuits; 7. know how to measure current and voltage; 8. use power factor; 9. calculate series and parallel circuit resistances; 10. find the current capacity of cables; 11. choose cable sizes; 12. calculate permissible cable lengths; 13. understand temporary electrical installations for construction sites; 14. calculate the total electrical loading in kilovolt-amperes and amperes for installation; 15. estimate the total cost of electricity likely to be consumed in an installation during normal use; 16. choose the correct fuse rating; 17. understand the operation of fuses and circuit-breakers; 18. know the distribution of electricity within buildings; 19. identify the use of isolating switches, distribution boards and meters; 20. understand earth bonding of services; 21. know the types of cable conduits and their applications; 22. understand the principles of ring circuits; 23. understand how electrical systems are tested; 24. be aware of telecommunications cables; 25. design lightning conductor systems; 26. identify the graphic symbols used on drawings.
292 Electrical installations Key terms and concepts alternator 292; apparent power 296; balanced load 292; bonding 294; cable-sizing calculations 299; cables, trunking and conduits 307; capacitor 296; cartridge fuse 305; distribution board 307; electrical measurements 310; electric shock 304; fault current 305; fuses and circuit-breakers 304; graphic symbols 314; IEE Wiring Regulations 299; kilowatts (kW) and kilovolt-amperes (kVA) 296; lightning conductor systems 312; line current 292; line, neutral and earth conductor 293; methods of testing 310; miniature circuit-breaker 305; national grid 292; Ohm’s law 295; power factor (PF) 296; real power 296; residual current device 305; ring circuit 308; series and parallel circuits 296; single- and three-phase 292; specific resistance 294; telecommunications 312; temperature coefficient of resistance 294; temporary electrical installations on sites 300; triple pole and neutral switch 308; voltage, current, power and resistance 295. Introduction The safe and economical use of electricity is of paramount importance to the building user and the world as it is the most highly refined form of energy available. Electricity production consumes up to three times its own energy value in fossil fuel, and electricity in its distributed form is potentially lethal. In this chapter the handling methods and safety precautions for utilizing electricity are explained and a range of calculations, which can easily be performed by the services designer or constructor prior to employing specialist help, is introduced. Electricity distribution The electrical power-generating companies supply electrical power into the national 400 kV grid system of overhead bare wire conductors. This very high voltage is used to minimize the current carried by the cables over long distances. Step-down transformers reduce the voltage in steps down to 33 kV, when it can be supplied to industrial consumers and to other transformer stations on commercial and housing estates. The electricity-generating alternator rotates at 50 Hz (3000 rev/mm) and has three coils in its stator. The output voltages and currents from each coil are identical but are spaced in time by one-third of a revolution, 120 ◦ . Each coil generates a sine wave or phase voltage that has the same heating effect as a 240 V continuous direct current supply. This is its root mean square (RMS) value. The RMS value of the three phases operating together is 415 V. Figure 13.1 shows the connections to a three-wire three-phase 415 V, 50 Hz alternating current supply entering a non-domestic building. Various circuits of different voltages are supplied from the incoming mains. Equal amounts of power are fed into each phase, and so it is important that power consumption within a building is equally shared by each line. The neutral wire is a live conductor in that it is the return path to the alternator for the current which has been distributed. Figure 13.2 shows a single-phase from one of the generator coils where the effective voltage is the RMS value: RMS = √ ∑ V 2 n n where V is the voltage at each of n measurements, say at 15 ◦ intervals. A balanced load, such as a three-phase electrical motor driving an air-conditioning fan, water pump or lift motor, does not produce a current in the neutral wire. This is because an alternating
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Building Services Engineering
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Building Services Engineering Fifth
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Contents Preface to fifth edition A
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Contents vii Sick building syndrome
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Contents ix Circuit design 294 Cabl
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Preface to fifth edition Building S
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Acknowledgements I am particularly
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Units and constants xv Table 2 Mult
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Symbols xvii Symbol Description Uni
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Symbols xix Symbol Description Unit
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2 Built environment Introduction Th
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4 Built environment Ventilation The
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6 Built environment (a) At full occ
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8 Built environment Table 1.2 Compa
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10 Built environment Because of the
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12 Built environment Visual display
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14 Built environment v = 7 m/s t a
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16 Built environment 1.4 Sling psyc
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18 Built environment 1.7 Thermistor
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20 Built environment t res = t g (1
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22 Built environment great care wit
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24 Built environment 16. An hotel l
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26 Built environment 37. Are any of
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28 Built environment building has a
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30 Built environment 73. What was t
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32 Energy economics Introduction Bu
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34 Energy economics 16. air-to-air
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36 Energy economics 1 kWh = 1 kWh
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38 Energy economics 2. Heat transfe
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40 Energy economics For solid fuel
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42 Energy economics gas cost = 1.80
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44 Energy economics Table 2.5 Carbo
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46 Energy economics EXAMPLE 2.8 A h
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48 Energy economics annual cost = u
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50 Energy economics EXAMPLE 2.12 Ex
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52 Energy economics l = 0.035 ( 1 0
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54 Energy economics Table 2.11 Valu
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56 Energy economics From Table 2.4
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58 Energy economics 3. Minimum outs
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3 Heat loss calculations Learning o
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62 Heat loss calculations Table 3.1
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64 Heat loss calculations Table 3.6
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66 Heat loss calculations Where onl
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68 Heat loss calculations The venti
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70 Heat loss calculations The surro
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72 Heat loss calculations The speci
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74 Heat loss calculations where R m
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76 Heat loss calculations The addit
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78 Heat loss calculations operation
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80 Heat loss calculations 2. The fo
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82 Heat loss calculations internal
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84 Heat loss calculations 27. Which
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86 Heating Key terms and concepts a
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88 Heating 4.2 Electrically heated
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90 Heating Sheet steel case Removab
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92 Heating Floor finish Screed with
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94 Heating Flue Return air plenum F
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96 Heating Table 4.1 Classification
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98 Heating Table 4.2 Heat output fr
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100 Heating Table 4.3 Flow of water
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102 Heating and, maximum available
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104 Heating This means that one vol
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106 Heating Performance testing A r
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108 Heating Electrical power genera
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110 Heating Combined heat and power
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112 Heating 3. A building energy ma
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114 Heating Connections are made to
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116 Heating remotely the MWh consum
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118 Heating 13. The two-pipe heatin
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120 Heating 27. Which is not correc
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122 Heating 39. Which of these is t
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124 Heating 4. Heat supplied is cha
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126 Ventilation and air conditionin
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6 Hot- and cold-water supplies Lear
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180 Hot- and cold-water supplies Wa
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182 Hot- and cold-water supplies po
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184 Hot- and cold-water supplies Ce
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186 Hot- and cold-water supplies st
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188 Hot- and cold-water supplies 0.
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190 Hot- and cold-water supplies 53
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192 Hot- and cold-water supplies an
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194 Hot- and cold-water supplies Ta
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196 Hot- and cold-water supplies Ta
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198 Hot- and cold-water supplies (a
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204 Hot- and cold-water supplies 49
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206 Soil and waste systems Introduc
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208 Soil and waste systems Open to
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210 Soil and waste systems 7. Bends
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212 Soil and waste systems The inte
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214 Soil and waste systems 40 mm wa
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216 Soil and waste systems Table 7.
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218 Soil and waste systems 50 mm ve
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220 Soil and waste systems 3. Long
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222 Surface-water drainage Table 8.
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224 Surface-water drainage Rectangu
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226 Surface-water drainage The solu
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228 Surface-water drainage 7. A PVC
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230 Below-ground drainage Design ca
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232 Below-ground drainage Manhole:
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234 Below-ground drainage From Fig.
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236 Below-ground drainage storage v
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238 Below-ground drainage 14. The f
Page 261 and 262: 240 Condensation in buildings mould
Page 263 and 264: 242 Condensation in buildings The w
Page 265 and 266: 244 Condensation in buildings EXAMP
Page 267 and 268: 246 Condensation in buildings This
Page 269 and 270: 248 Condensation in buildings Tempe
Page 271 and 272: 250 Condensation in buildings and,
Page 273 and 274: 252 Condensation in buildings EXAMP
Page 275 and 276: 254 Condensation in buildings Tempe
Page 277 and 278: 256 Condensation in buildings For t
Page 279 and 280: 258 Condensation in buildings 4. Ev
Page 281 and 282: 11 Lighting Learning objectives Stu
Page 283 and 284: 262 Lighting Table 11.1 Typical val
Page 285 and 286: 264 Lighting Light sources 9 9 9 Wi
Page 287 and 288: 266 Lighting Utilization factor The
Page 289 and 290: 268 Lighting From Table 11.3, for a
Page 291 and 292: 270 Lighting Table 11.4 Lamp data.
Page 293 and 294: 272 Lighting number of lamps = 12.8
Page 295 and 296: 274 Lighting 3. Sketch and describe
Page 297 and 298: 276 Lighting 4. Insufficient inform
Page 299 and 300: 278 Lighting 3. 800 lm/m 2 . 4. 260
Page 301 and 302: 12 Gas Learning objectives Study of
Page 303 and 304: 282 Gas Open to atmosphere Rubber p
Page 305 and 306: 284 Gas EL = (1.25 × 34) m = 42.5
Page 307 and 308: 286 Gas become exhausted. SNG will
Page 309 and 310: 288 Gas are ignited and an air flow
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Page 321 and 322: 300 Electrical installations For1mm
Page 323 and 324: 302 Electrical installations Table
Page 325 and 326: 304 Electrical installations Incomi
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Page 329 and 330: 308 Electrical installations Starte
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Page 333 and 334: 312 Electrical installations Test o
Page 335 and 336: 314 Electrical installations Joint
Page 337 and 338: 316 Electrical installations 4. 100
Page 339 and 340: 318 Electrical installations 39. Wh
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Page 343 and 344: 322 Room acoustics 20. understand t
Page 345 and 346: 324 Room acoustics pump blades and
Page 347 and 348: 326 Room acoustics ceiling, Q is 4.
Page 349 and 350: 328 Room acoustics Table 14.2 Solut
Page 351 and 352: 330 Room acoustics Table 14.3 Fan s
Page 353 and 354: 332 Room acoustics Table 14.4 Illus
Page 355 and 356: 334 Room acoustics (Sound Research
Page 357 and 358: 336 Room acoustics The target room
Page 359 and 360: 338 Room acoustics Table 14.6 Noise
Page 361 and 362: 340 Room acoustics 100 90 80 70 Sou
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342 Room acoustics 24. A forced-dra
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344 Room acoustics The room directi
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346 Room acoustics 3. Multiple sour
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348 Room acoustics 55. Which is not
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350 Fire protection computer monito
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352 Fire protection halogen gas, wh
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354 Fire protection the reach of tu
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356 Fire protection Range pipe Spri
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358 Fire protection Fire compartmen
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360 Fire protection 16. Which are c
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362 Plant and service areas Key ter
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364 Plant and service areas 2.0 1.5
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366 Plant and service areas Fuel st
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368 Plant and service areas a minim
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370 Plant and service areas An unde
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372 Plant and service areas Air cha
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374 Plant and service areas 100 mm
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376 Plant and service areas Fire co
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378 Plant and service areas Table 1
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380 Plant and service areas 11. Wha
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17 Mechanical transportation Learni
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384 Mechanical transportation Table
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386 Mechanical transportation Crowd
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388 Mechanical transportation Hydra
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390 Mechanical transportation 4. Co
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18 Question bank Learning objective
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394 Question bank 8. Which correctl
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396 Question bank 5. This building
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398 Understanding units Questions 1
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400 Understanding units 15. Which i
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402 Understanding units 29. Which o
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404 Understanding units 43. Which i
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Appendix: answers to questions Chap
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408 Appendix Chapter 3 Heat loss ca
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410 Appendix 4. 0.007469 kg H 2 O/k
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412 Appendix 32. 5 33. 5 34. 3 35.
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414 Appendix 23. Lighting 1200 h/ye
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416 Appendix 27. 37 dB. 28. 39 dB.
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418 Appendix 15. 5 16. 2 17. 5 18.
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References Action Energy, Departmen
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Index Absorption 154, 324 Absorptio
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424 Index Gas burner controls 289 G
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426 Index Sensible heat gains 137 S
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Building Services Engineering 5th Edition Handbook

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