ARC 256: Building Services Exam

Questions and Answers

What is one source of electricity generation?

Wind

Solar Energy

River Flow

All of the above (correct)

What type of current flows continuously in the same direction?

Direct Current (D.C.)

Alternating current (A.C.) is induced into coils by moving magnetic fields.

True

The resistance of a conductor is influenced by its specific resistance, length, and ______.

cross-sectional area Signup and view all the answers

What is the maximum voltage drop allowed for a 240V nominal supply?

4% Signup and view all the answers

What is a transformer used for?

Both A and B Signup and view all the answers

What type of cable is most commonly used for electrical wiring in buildings?

PVC Insulated / PVC Sheath Cables Signup and view all the answers

A cable is a conductor surrounded by ______.

insulative material Signup and view all the answers

Match the following electrical terms with their definitions:

Direct Current (D.C.) = Current flowing in one direction Alternating Current (A.C.) = Current that periodically reverses direction Transformer = Device that changes voltage levels Voltage Drop = Reduction in voltage in a circuit Signup and view all the answers

What is the function of a lightning conductor?

To protect buildings from lightning strikes Signup and view all the answers

The temperature coefficient of resistance of copper is 0.00428Ω/Ω°C at 0°C.

True Signup and view all the answers

What is the main purpose of the Building Regulations concerning electricity?

To ensure safety and accessibility for all users Signup and view all the answers

How is the number of fittings calculated in lighting design?

Number of fittings = lux × working plane area m2 / (LDL × UF × MF) Signup and view all the answers

What is the spacing-to-height ratio (SHR) assumed for the New Streamlite double-lamp luminaires?

1.75 Signup and view all the answers

What is the illuminance required in the lighting design?

600 lm/m2 Signup and view all the answers

What is the maintenance factor (MF) assumed for the lighting design?

0.9 Signup and view all the answers

Calculate the height (H) of fittings above the working plane in the drawing office.

2.15 m Signup and view all the answers

What is the utilization factor for a room index of 3?

0.79 Signup and view all the answers

If 30 luminaires are used at 140 W each, what is the total power consumption?

4200 W Signup and view all the answers

What is the electrical power consumption per square meter for the described room?

23.86 W/m2 Signup and view all the answers

Calculate the percentage increase in electrical resistance for a 28m copper conductor when temperature rises to 45 ◦C from 20 ◦C.

To be calculated Signup and view all the answers

Find the maximum length of a 6mm2 cable that can be used on a 240V circuit.

To be determined Signup and view all the answers

How is the room index defined in a lighting design?

Room Index = lW / (H(l + W)) Signup and view all the answers

Calculate the utilization factor for a bare fluorescent tube light fitting in a 5m × 3.5m room.

To be calculated Signup and view all the answers

What power consumption is associated with the supermarket lighting setup?

140 W per fluorescent tube fitting Signup and view all the answers

Calculate the number of luminaires needed for a supermarket room with dimensions 20m × 15m and a working plane height of 1m.

To be determined Signup and view all the answers

What is the maximum current rating for a 1 mm² electrical cable?

15 A Signup and view all the answers

What is the maximum voltage drop allowed for a 240 V circuit for an immersion heater?

9.6 V Signup and view all the answers

What is the length of the maximum run for 1.5 mm² cable on a 240 V circuit to a 3 kW heater?

26.5 m Signup and view all the answers

What is the resistance metric that must not exceed 1Ω during the testing of a protective conductor?

1 Ω Signup and view all the answers

Which tests are conducted for effective earthing?

All of the above Signup and view all the answers

What is the maximum allowed resistance to earth for a lightning conductor system?

10 Ω Signup and view all the answers

What is the luminous intensity measurement unit?

Candela (cd) Signup and view all the answers

The efficiency of lamps in lumens per watt is referred to as _____ .

Efficacy Signup and view all the answers

What is the efficacy of a lamp?

Lumens per watt (lm/W) Signup and view all the answers

What is the typical service life of GLS lamps?

2000 hours Signup and view all the answers

What is the total lumens needed at the working plane to design a lighting scheme for an office that is 8 m long by 7 m wide, requiring an illumination level of 400 lux?

22400 lumens Signup and view all the answers

Study Notes

Course Overview: ARC 256 - Building Services

Course credits: 2
Focus on design and installation of essential building services.

Course Content

Electricity and Lighting
Covers electricity generation, circuit design, and lighting systems.
Water Supply, Sanitary Appliances, and Drainage Systems
Encompasses water supply networks, drainage systems, and plumbing design.
Ventilation and Air Conditioning
Involves ventilation rates and ducting design.
Fire Control and Equipment
Includes active and passive fire control measures.

Course Objectives

Learn cold-water pipe system design and basic pipe-sizing calculations.
Design waste and drain systems per building usage and sanitary appliances.
Understand ventilation air quantity calculations and design criteria for air movement control.
Calculate necessary electrical parameters, including current and power in circuits.
Design illumination levels for indoor spaces through effective lamp spacing.

Assessment Criteria

Continuous Assessment (30%): Includes coursework, mid-semester exam, and attendance.
End of Semester Exam (70%): Consists of multiple-choice questions and essay-type questions requiring calculations.
Overall assessment is cumulative for a total of 100%.

Electricity Generation

Sources of Electricity
Includes hydro, thermal (from steam), wind, solar, nuclear, coal, and natural gas.
Transformers
Used to step-up or step-down voltage levels for efficient power distribution.

Types of Current

Alternating Current (A.C.)
Changes direction periodically; seen in most home appliances.
Direct Current (D.C.)
Flows in one direction; produced by batteries.

Public Distribution of Electricity

High voltage transmission to urban areas at 132kV or 33kV; converts to lower voltages for residential use via substations.
Load balancing across phases to prevent overloads.

Electrical Supply to Buildings

Single Phase Supply
Generally used for small buildings with one phase wire and neutral.
Three Phase Supply
Discussed in the context of load distribution and efficiency.

Circuit Design

Resistance varies with material, temperature, and dimensions.
Ohm’s law relates voltage (V), current (I), and resistance (R).
Examples demonstrate calculations for resistance and power in circuits.

Cable Specifications

Cables described by cross-sectional area; commonly used materials include copper and aluminum.
PVC insulation is common due to its durability and low moisture absorption.
Color coding of cables: green/yellow for earth, orange for special cables.

Testing of Electrical Installations

Safety verification through regular inspections and testing for correct polarity and earthing efficiency.
Visual checks and earth conductor tests ensure installation safety.

Key Tables

Socket Requirements: Specific minimum socket quantities in various rooms like living rooms and kitchens.
Appliance Load Fuses: Indicates load ratings for different plug fuse sizes.
Cable Capacities: Includes maximum current ratings for various cable sizes, essential for safety and functionality in installations.

These notes summarize core elements of the ARC 256 Building Services course, providing a helpful study reference for key principles and application in electrical systems and building service installations.### Impedance Testing

Earth Loop Impedance Test: Conducted using a line-earth loop impedance test meter with a 13A plug connected to power sockets.
Operation: The meter injects current into the earth conductor, which flows to a transformer and back, measuring resistance.
Residual Current Device Test: Utilizes a transformer supplying 45V to induce a short-circuit current from neutral to protective conductor, causing the device to trip.
Consumer Earth Electrode Resistance Measurement: A test electrode is inserted into the ground to measure resistance using a 50 Hz current between the electrode and consumer's earth electrode.

Insulation Resistance Tests

Measurement Method: An insulation test meter connects between line and protective conductors, applying 500V DC.
Resistance Requirement: Minimum resistance of 0.5MΩ is mandatory for safety compliance.

Ring Circuit Continuity Tests

Testing Process: Resistance of each ring circuit is checked at the distribution board using an ohmmeter.
Checkpoints: Probes are connected across line, neutral, and protective conductors to confirm continuity.

Compliance Standards

IEE Wiring Regulations: Testing must comply with IEE regulations conducted by a qualified electrical engineer.
Certificates: IEE Completion and Inspection Certificates are issued post-testing.

Lightning Conductors

Protection System Criteria: Requirement depends on building construction, isolation, height, topography, and lightning frequency (BS Code of Practice 326: 1965).
Conductors: Options include copper and aluminum rods, PVC-covered strips, and copper braid.
Installation Guidelines:
- Air terminals above the structure's highest point.
- Down conductors bolted to prevent side flashing.
- Ground termination with various electrode types including earth rods.
Ground Resistance Limit: Maximum electrical resistance for the whole system is 10Ω.

Earth Resistivity Values

Typical earth resistivity:
- Clay: 10 Ωm
- Chalk: 50 Ωm
- Clay shale: 100 Ωm
- Slatey shales: 1000 Ωm

Lightning Conductor Design Example

Design Parameters: For a 30m high building in a thunderstorm-prone area, using 4m long electrodes.
Conductor Resistance Calculation:
- Copper specific resistance is 0.0172μΩm.
- Down conductor resistance: 0.092Ω.
- Earth electrode resistance exceeds 10Ω; two electrodes in parallel yield 7.4Ω combined resistance.

Lighting Definitions

Luminous Intensity (cd): Measures light magnitude reflected from a surface.
Luminous Flux (lm): The visible light energy emitted by a source.
Illuminance (lux): Light intensity per area.
Efficacy (lm/W): Efficiency of the lamp.

Illumination Levels Table

Guidelines provided for different activities, e.g., office work (500 lux), laboratory (500 lux), and classrooms (300 lux).

Lighting Design Calculations

Formula: E = I/d² for illumination from perpendicular sources; E = (I cosѲ)/d² for non-perpendicular sources.
Utilization Factor: Reflects light distributed efficiency and room configuration, values range from 0.03 to 0.75.

Maintenance Factor

Definition: Accounts for reduced light output due to dust on lamps, generally set at 0.8, or 0.9 if lamps are regularly cleaned.

Room Index Calculation

Formula: Room index = lW/(H(l + W)), where l is length, W is width, and H is height from the working plane.

Example Calculation for Lighting Requirements

Determination of the number of fittings based on lux requirements, working plane area, LDL, UF, and MF through specified formulas.

Case Studies of Office Lighting

Detailed examples show how to determine the optimal number of fixture arrangements based on area, illumination requirements, and lamp efficacy.

Additional Questions

Practical Problems: Examples of calculations include resistance change with temperature, maximum cable length for current capacity, room index for office dimensions, and luminaire spacing calculations for efficient lighting arrangements.

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Description

Test your knowledge on Building Services as covered in ARC 256 at Kwame Nkrumah University of Science and Technology. This quiz focuses on the design and installation of various building service systems, including electricity, plumbing, and HVAC systems.