Building Electrical Services Design For Hostel

ABSTRACT

The main objective of the project is to design the building electrical services for a hostel along Nyerere road and located in Nairobi, Kenya. The site plan has one building with a total of six, (6) floors. Due to the location, the most reliable source of electrical power is the mains national grid power. In order to achieve the main objective and to specify the size and number of back-up generators to be employed, the final circuits consisting of lighting and power sockets is designed first. The lighting design is done using the lumen method which takes into consideration the size and use of the room being lit. Power points layout design is done by considering the needs of the final user of the premises in every room; this ensures that the need for electrical power is  fulfilled in the design. The final circuits are to be supplied by fifteen, (15) consumer units. These consumer units are then all distributed on one, (1) distribution board, ensuring that all the single- phase loads are balanced almost equally on each phase with 341.389 amperes on red phase,

333.472 amperes on the yellow phase and 335.972 amperes on the blue phase. This guaranteed that cables and distribution equipment are utilized much more effectively due to small differences in current on each phase. The load of the entire building is 308.6 kW or 385.75 kVA and so the power back-up systems design has one hooded diesel generator rated 450 kVA. This is located at a convenient area and caged within the site compound. To ensure co-ordinated operation of the Miniature Circuit Breakers (MCB), and Moulded Case Circuit Breakers (MCCB) when safeguarding against the effects of overloads and short circuits, discrimination between the devices is observed. This has enabled the system to switch off only the breaker closest to the fault without disruption of supply to other areas. Finally lightning protection is done to safeguard against the effects of a lightning stroke. With this system the hostel will have safe, reliable and expandable power supply.

TABLE OF CONTENTS

DEDICATION………………………………………………………………………………………………………………….. i

ACKNOWLEDGEMENTS…………………………………………………………………………………………………. ii

DECLARATION AND CERTIFICATION…………………………………………………………………………… iii

ABSTRACT……………………………………………………………………………………………………………………. iv

CHAPTER 1……………………………………………………………………………………………………………………. 1

• INTRODUCTION…………………………………………………………………………………………… 1
• Objectives……………………………………………………………………………………………………………….. 1
• Prelude…………………………………………………………………………………………………………………… 1
  • Building Electrical Services Design…………………………………………………………………………. 2
  • Codes and Standards…………………………………………………………………………………………….. 2
  • End – User Accessories…………………………………………………………………………………………. 2

CHAPTER 2……………………………………………………………………………………………………………………. 3

• THEORY AND BACKGROUND………………………………………………………………………. 3
• Lighting Design………………………………………………………………………………………………………… 3
  • Hostel Lighting Design………………………………………………………………………………………….. 3
  • Illuminance Recommendations………………………………………………………………………………. 4
  • Light Sources………………………………………………………………………………………………………. 4
  • Lumen Method of Lighting Design………………………………………………………………………….. 5
  • Light Switches……………………………………………………………………………………………………… 6
• Electrical Power Circuits……………………………………………………………………………………………. 6
  • Socket Outlets……………………………………………………………………………………………………… 6
  • Kitchen Unit………………………………………………………………………………………………………… 7
• Electrical Service Network…………………………………………………………………………………………. 7
  • Diversity…………………………………………………………………………………………………………….. 7
  • Power Circuit Design…………………………………………………………………………………………….. 7
  • Consumer Units…………………………………………………………………………………………………… 8
  • Distribution Board………………………………………………………………………………………………… 9
  • Switch-Boards……………………………………………………………………………………………………… 9
  • Commercial Back-Up Diesel Power Generators………………………………………………………. 10
  • Wiring 11
  • Cable Sizing………………………………………………………………………………………………………. 11
• Protection Systems………………………………………………………………………………………………….. 11
  • Overload Protection……………………………………………………………………………………………. 12
  • Short Circuit Protection……………………………………………………………………………………….. 12
  • Protection System Equipment……………………………………………………………………………….. 13
  • Discrimination and Protection System Co-ordination……………………………………………….. 13
  • Lightning Protection……………………………………………………………………………………………. 14

CHAPTER 3………………………………………………………………………………………………………………….. 16

• PROJECT WORK AND IMPLEMENTATION…………………………………………………… 16
• Site Location………………………………………………………………………………………………………….. 16
• Site Plan and Introduction………………………………………………………………………………………… 16
  • Sample Lumen Method of Lighting Design Calculation for One Hostel Room 16
  • Sample Power Points Layout Design for One Hostel Room………………………………………. 19
• Entire Hostel Lighting Fittings Design and Power Points Layout Designs…………………………. 20

CHAPTER 4………………………………………………………………………………………………………………….. 21

• DESIGN ANALYSIS AND DISCUSSIONS……………………………………………………….. 21
• Design Analysis Based on Load Calculations and Circuits Arrangements………………………… 21
  • Introduction………………………………………………………………………………………………………. 21
  • Lower Floor………………………………………………………………………………………………………. 22
  • Upper Ground Floor……………………………………………………………………………………………. 23

CHAPTER 5………………………………………………………………………………………………………………….. 28

• DISTRIBUTION SYSTEM TOPOLOGY…………………………………………………………… 28
• Consumer Unit, (CU) Design and Specifications…………………………………………………………. 28
  • Consumer Unit, CU UGF 1………………………………………………………………………………….. 30
  • Consumer Unit Total Single-Phase load calculations, Total Load Currents Drawn, Cable Length and Cable Size Selection from the Distribution Board, (DB) feeding the CU…………………………… 31
• Distribution Board, (DB) Design and Specifications…………………………………………………….. 33
  • Single-Phase Loads Distribution Board Design and Specifications……………………………… 33
  • Three-Phase Loads Distribution Board Design and Specification……………………………….. 37
• Power Back-Up Generator……………………………………………………………………………………….. 41
  • Size of Back-Up Generator………………………………………………………………………………….. 41
  • Sizing of Cable of the Back-Up Generator……………………………………………………………… 42
• Electrical Distribution Reticulation…………………………………………………………………………….. 43
• Electrical Distribution Protection System based on Fault Current Levels at Various Points in the Installation 44
  • Fault Current Level at the Switch-Board……………………………………………………………….. 44
  • Fault Current Levels at the Beginning of Final Circuits……………………………………………. 45
  • Discrimination between CUs and DBs………………………………………………………………….. 48
  • Discrimination between DBs and the Switch-Board……………………………………………….. 49
  • Discrimination between Moulded Case Circuit Breaker, (MCCB 1) and Switchboard….. 50
  • Discrimination between Generator Moulded Case Circuit Breaker, (MCCB 2) and Switch- Board 51
• Lightning Protection Design……………………………………………………………………………………… 52
• Power Factor Correction………………………………………………………………………………………….. 53

CHAPTER 6………………………………………………………………………………………………………………….. 55

6.0 CONCLUSIONS……………………………………………………………………………………………………….. 55

CHAPTER 7………………………………………………………………………………………………………………….. 56

• RECOMMENDATION FOR FUTURE WORK…………………………………………………… 56
• Software for Building Electrical Services Design…………………………………………………………. 56
• Bill of Quantities……………………………………………………………………………………………………. 56
• Earth Faults……………………………………………………………………………………………………………. 56

CHAPTER 8………………………………………………………………………………………………………………….. 57

8.0 REFERENCES………………………………………………………………………………………………………….. 57

CHAPTER 9………………………………………………………………………………………………………………….. 59

9.0 APPENDICES…………………………………………………………………………………………………………… 59

Appendix A-1: Auto Computer Aided Designs, (AUTOCAD) for Lighting Design and Power Points Layout Design……………………………………………………………………………………………………………………….. 59

Appendix A-2: Lightning Protection Design…………………………………………………………………….. 60

Appendix B: Consumer Units Designs and Specifications…………………………………………………. 61

Appendix C: IEE tables………………………………………………………………………………………………… 62

Appendix D: MEM Catalogue Extracts……………………………………………………………………………. 64

Appendix E: Power Back-Up Generator Data Sheet and Performance…………………………………. 66

Appendix F: Utilization Factors……………………………………………………………………………………… 67

CHAPTER 1

INTRODUCTION

Objectives

The main objective of the project is to do a building electrical services design for a hostel along Nyerere road. In order to achieve the main objective, the project work is split into other smaller but related sections and scopes with specific targets to be met. The areas of utmost interest and covered exhaustively and in detail in this project are thus:

• Lighting design
• Power points layout design
• Cables sizing
• Power back-up system
• Protection system design
• Discrimination and co-ordination system
• Power factor correction

 

Prelude

Engineering specialization consists of various fields. One of these fields is the building design and construction which has six different categories: civil, structural, mechanical, electrical, environmental and materials engineering.¹

This project will focus on the electrical category of building design and construction from the electrical services design engineer’s perspective rather than that of the installation electrician or architect. The main focus is to ensure that the electrical system meets the following criteria:

• Reliability
• Durability
• Maintainability

1 Sidney M. Levy, “Construction Process Planning and Management, An Owners Guide to Successful Projects” 2007, Page 47

• Efficiency
• Economy²

Building Electrical Services Design

Any electrical requirements are greatly influenced by the needs of the client or end-user of the building. The end-user is more interested in the appearance and the function of the various appliances whereas the design engineer is interested in the complete electrical design and installation.

Codes and Standards

Every building must follow the laid down local, national or international codes and standards that it is associated with its location and the acceptable codes and standards for that region.

The international codes and standards are developed by international standardization organizations such as the Institute of Electrical and Electronics Engineers (IEEE). They prepare standards that are adoptable and acceptable on a global scale.

National codes and standards are developed by associations within a particular country or region which are then applied within local or national legislation in order to be enforceable by law.³

Such codes and standards have to be considered by the design engineer in order for the final work to be acceptable to the client and the local authorities.

End – User Accessories

These are the various electrical equipments which are utilized by the end user in controlling the function of the electrical installations made within the living or working space. They are called accessories “because they are accessory to the wiring.” ⁴ These accessories include switches, socket outlets, fused connection units, and the kitchen units.

2 U.S. Army Corps of Engineers, “Electrical Power Supply and Distribution” Technical Manual No. 5-811- 1, Page 1-1

3 http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70&cookie_test=1

4 Barrie Rigby, “Design of Electrical Services for Buildings” 4^th Edition, Page