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Building Services Engg. (Electrical installations)

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  • thank u very much very helpful presentation i have 3 different building loads on building 1 is 2056A building2. 2345A building3.2567A HOW CAN I SIZE MAIN CIRCUIT BREAKER OR SWITCG GEAR FOR INSTALLATION
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Building Services Engg. (Electrical installations)

  2. 2.  Most domestic premises receive a single-phase supply of electricity from an areaelectricity board at a rating of 240 volts andfrequency of 50 hertz. The area electricity boards cable, from whichthe domestic supply is taken, consists of fourlines, three lines each carrying a 240 voltsupply and the fourth is the common returnline or neutral25-Apr-13 2
  3. 3.  Neutral is connected to earth at thetransformer or substation as a safetyprecaution should a fault occur on theelectrical appliance. Each line or phase is tapped in turn togetherwith the neutral to provide the single-phase240V supply25-Apr-13 3
  4. 4.  The supply or intake cable may enterbuilding in two waysI. Underground ductII. Overhead supply. An underground supply is preferred since allof the electrical service is hidden.25-Apr-13 4
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  6. 6.  From the sealing chamber the supply passesthrough the meter, which records theelectricity consumed in units ofkilowatt/hours, to the consumer unit whichhas a switch controlling the supply tothe circuit breakers or circuit fuses These fuses are a protection against excesscurrent or overload, the fuse or circuitbreaker will isolate the circuit from the sourceof the problem.25-Apr-13 6
  7. 7.  The consumer unit should be fitted close tothe point of service entry and from here theservice is divided into a number of sub-circuits. It is normal in a domestic installation toseparate power circuits and lighting circuitsso that if a fault occurs then not all socketoutlets or lights are isolated.25-Apr-13 7
  8. 8.  Sometimes an external cabinet is used foreasy meter reading.This is located in anoutside wall as shown below.EXTERNALCABINET25-Apr-13 8
  9. 9.  When deciding on the number of circuits for ahouse, a useful rule is; one power circuit forevery 100m2 of floor area. In larger houses this means that two circuitscan be used for power socket outlets, in atwo-storey house this would be one circuit forupstairs and one for downstairs. In some larger houses a separate powercircuit is also installed for the garage / utilityarea25-Apr-13 9
  10. 10.  In all domestic installations a separate powercircuit is required for the cooker since theelectrical demand is likely to be high.Theimmersion heater in the hot water cylindercan also be supplied from a separate circuitsince a 3kW load is quite high. Ring circuits are used as a safe and economicmethod of distribution of electricity to socketoutlets. Many consumer unit manufacturers produce8 way and 12 way units.25-Apr-13 10
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  13. 13.  Protection against electric shock is providedby insulating and placing live parts out ofreach in suitable enclosures, earthing andbonding metal work and providing fuses orcircuit breakers. A fuse or miniature circuit breaker (MCB) willdisconnect the supply automatically beforethe overload current can cause a rise intemperature which would damage theinstallation.25-Apr-13 13
  14. 14.  An isolator is a mechanical device, which isopened manually and is provided so that thewhole of the installation, one circuit or onepiece of equipment may be cut off from thelive supply. In addition, a means of switching off formaintenance or emergency switching mustalso be provided. In practice it is the aim to bring the Electricalsupply to the appliance with as small a loss ofvoltage through the conductor as possible. This means that the wiring must have thesmallest resistance that is economical25-Apr-13 14
  15. 15.  The electrical distribution system in high riseflats and office buildings uses a busbar system. A busbar is a solid copper bar that carries theelectrical current. The busbars run vertically inside trunking andare supported by insulated bars across thetrunking chamber. The electrical supply to each floor is connectedto the rising main by means of tap-off units.25-Apr-13 15
  16. 16.  To balance electrical distribution across thephases, connections at each floor should bespread between the phase bars. To prevent the spread of fire and smoke, firebarriers are incorporated with the busbarchamber at each compartment floor level. The chamber must also be fire stopped to thefull depth of the floor.25-Apr-13 16
  17. 17.  The types of light fitting that we use in modernbuildings can be divided into five sections.1. Decorative lighting2. Commercial lighting3. Industrial lighting4. Outdoor lighting5. Emergency lighting25-Apr-13 17
  18. 18. Quantity of light The amount of light emitted from a lightfitting is given in lumens (lm). A lumen is the unit of luminous flux. The amount of light falling on a surface ismeasured in lux. One lux is equal to 1 lumen per square metre…….. 1 lux = 1 lm/m2.25-Apr-13 18
  19. 19. Illuminance (lux) Activity Area100 Casual seeing Corridors, changing rooms, stores150 Some perception of detail Loading bays, switch rooms, plant rooms200 Continuously occupied Foyers, entrance halls, dining rooms300 Visual tasks moderately easy Libraries, sports halls, lecture theatres.500 Visual tasks moderately difficultGeneral offices, kitchens, laboratories, retailshops.750 Visual tasks difficult Drawing offices, meat inspection, chain stores.1000 Visual tasks very difficultGeneral inspection, electronic assembly,paintwork, supermarkets.1500 Visual tasks extremely difficult Fine work and inspection, precision assembly.2000 Visual tasks exceptionally difficultAssembly of minute items, finished fabricinspection.25-Apr-13 19
  20. 20. ND PHTGRPHY25-Apr-13 20
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