BS 2 5 electrical installatition

BUILDING SERVICES TWO (BLD60503)

ELECTRICAL INSTALLATION

Prepared by Tan Hee Chai

BUILDING | SERVICES | TWO (BLD60503)


1.The electrical loads will be classified according To Load Function as follows:

1. Lighting Electrical Load.2. Receptacles / General / Small Appliances Electrical Load.3. Power Electrical Loads.

1- Lighting electrical loads

a- What is light? Visible light is electromagnetic radiation with a wavelength that is visible to the eye


b- What are the main sources of light? there are two main sources of light which are as follows:

1- Natural light (day light or sun light) source

Sunlight is electromagnetic radiation by sun and which includes the full spectrum of visible light (as well as frequencies beyond the sensitivity of the eye, known as ultra violet and infrared)

2- Artificial light sources

Artificial light sources are other sources of light which developed to compensate for /assist the natural light. It will have different frequencies and wavelengths that determine the light color.


Effects of Using Day Lighting Source in Electrical Design

1- What is Importance of day lighting in electrical lighting design?

A Particular attention must be given to day lighting while designing a building lighting system due to the following:

•Day lighting is used to maximize visual comfort inside the buildings.

•Day lighting is used to reduce energy use by the following methods:

1.Reducing the use of artificial (electric) lighting by simply installing fewer electric lights because daylight is present, or by dimming/switching electric lights automatically in response to the presence of daylight.2.Using passive solar technology for heating or cooling different spaces inside the building.


2- What are the main characteristics of day lighting source?

The daylight entering a building may include direct sunlight when the window has a view of the sun, as well as diffuse sunlight that has been refracted by clouds, and reflected from various surfaces such as clouds, ground or other buildings.

•Daylight can therefore vary greatly with weather conditions, ranging from total cloud cover to clear sky with direct sunlight.

•The effectiveness of daylight as a light source is measured as the “Daylight Factor”.


Daylight Factor

It is the ratio of internal light level to external light level and is defined as follows:

DF = (Ei / Eo) x 100%

Where:

Ei = illuminance due to daylight at a point on the indoors working plane,

Eo = simultaneous outdoor illuminance on a horizontal plane from an unobstructed hemisphere of overcast sky.


•Daylight factors are used to determine if the natural lighting levels in a space will be sufficient for the occupants of the space to carry out their normal duties.

•Calculating daylight factors requires complex repetition of calculations and thus is general undertaken by a proprietary computer software product such as Radiance.• •CIBSE Lighting Guide 10 (LG10-1999) which broadly bands average daylight factors into the following categories:

1.DF Under 2 – Not adequately lit – artificial lighting will be required. 2.DF Between 2 and 5 – Adequately lit but artificial lighting may be in use for part of the time. 3.DF Over 5 – Well lit – artificial lighting generally not required except at dawn and dusk – but glare and solar gain may cause problems.


3- What are the types of day lighting technologies?

there are two types of technology that are used for utilizing the day lighting source as follows:

1- Active day lighting

It is a system of collecting sunlight using a mechanical device to increase the efficiency of light collection for a given lighting purpose. Active day lighting systems are different from passive day lighting systems in that passive systems are stationary and do not actively follow or track the sun


2- Passive day lighting

It is a system of both: collecting sunlight using static, non-moving, and non-tracking systems such as Windows, Sliding glass doors, most skylights, light tubes, and reflecting the collected daylight deeper inside with elements such as light shelves. Passive day lighting systems are different from active day lighting systems in that active systems track and/or follow the sun, and rely on mechanical mechanisms to do so.


4- What are the Common Methods for using Passive day lighting technology in a building?

there are many methods for using Passive day lighting technology in a building but the common ones will be as follows:

1- Windows Windows are the most common way to admit daylight into a space. Their vertical orientation means that they selectively admit sunlight and diffuse daylight at different times of the day and year.


2- Skylight


It is any horizontal window, roof lantern placed at the roof of the building, often used for day lighting. Generally it is made from White translucent acrylic which makes the transmitted light to be perfectly diffused and distributed evenly over affected areas and reduces the transmitted heat inside the building. Skylights admit more light per unit area than windows, and distribute it more evenly over a space.

The optimal area of skylights varies according to climate, latitude, and the characteristics of the skylight, but is usually 4-8% of floor area.

With proper skylight design, there can be significant energy savings in commercial and industrial applications up to 80 percent according to the US Department of Energy's Federal Energy Management Program.

In terms of cost savings, the DOE reported that many commercial buildings can reduce total energy costs by up to one-third through the optimal use of day lighting.


3- Light shelves


Light shelves are an effective way to enhance the lighting from windows on the equator-facing side of a structure, this effect being obtained by placing a white or reflective metal light shelf outside the window.

Usually the window will be protected from direct summer season sun by a projecting eave. The light shelf projects beyond the shadow created by the eave and reflect sunlight upward to illuminate the ceiling.

This reflected light can contain little heat content and the reflective illumination from the ceiling will typically reduce deep shadows, reducing the need for general illumination.


4- Tubular Day lighting Devices (TDDs)


It uses modern technology to transmit visible light through opaque walls and roofs.

The tube itself is a passive component consisting of either a simple reflective interior coating or a light conducting fiber optic bundle.

It is frequently capped with a transparent, roof-mounted dome 'light collector' and terminated with a diffuser assembly that admits the daylight into interior spaces and distributes the available light energy evenly.


5- Smart glass


It is the name given to a class of materials and devices that can be switched between a transparent state and a state which is opaque, translucent, reflective, or retro-reflective. The switching is done by applying an electric voltage to the material, or by performing some simple mechanical operation. Windows, skylights, etc., that are made of smart glass can be used to adjust indoor lighting, compensating for changes of the brightness of the light outdoors and of the required brightness indoors.


5- Problems generated from using day lighting source

Two potential problems associated with the use of day lighting buildings are as follows:

1- Glare Glare occurs when a bright light source such as the sun is in the field of view of users. It can also occur when reflections of the sun are in the field of view.

2- Heat Daylight is always associated with heat, and the challenge is to maximize the benefit from daylight with minimum heat gain.

all the above information will guide the electrical designer for utilizing the Daylight Source (in cooperation with the architecture engineer) to have the best lighting design which meet the user requirements and in same time increase energy savings in the buildings.


1.Artificial lighting

Artificial light sources are other sources of light which developed to compensate for or assist the natural light. It will have different frequencies and wavelengths that determine the light color.

First :Artificial light sources

Artificial light sources are categorized by the technology used to produce the light. There's dozens of sources, with a few common in household applications and others more suitable for industrial uses. The five most common light sources are as follows:

1.Incandescent lamp. 2.Compact fluorescent lamp. 3.Fluorescent tube. 4.Discharge lamps. 5.Light Emitting Diode (LED).


1- Incandescent lamp:Until recently the most common electric light source was the incandescent lamp. This is still widely used, although its relatively low energy efficiency is leading to its replacement by other more efficient lamps such as the CFL.

The connection to a light fitting is either by screw thread or bayonet.

A large variety of shapes, sizes and power is available, as well as different colour ranges. Typical lamps for household use range from about 40 to 100 W, giving a light output of 420 to 1360lm at the typical lamp efficiency of about 12%.


2- Compact fluorescent lamp:


The compact fluorescent lamp (CFL) was designed as a more efficient replacement for incandescent lamp.

It is supplied with the same fixing system (screw or bayonet), and can be used in many light fittings designed for incandescent lamps.

Power ratings of CFLs that can provide approximately the equivalent light output to incandescent lamps are shown in the table below, together with their efficacy ratings.


3- Fluorescent tube:


Fluorescent tubes are the main form of lighting for offices and commercial buildings.

They are a form of gas discharge lamp, and are formed in a long thin glass cylinder with contacts at either end that secure them to the fitting (or luminaire) and provide the electrical connection.

The tube contains mercury vapour at low pressure, and the inner wall of the glass is coated with a phosphor that reacts to ultra-violet radiation. When electricity is passed through the vapour it emits UV radiation that is converted by the phosphor to visible light.

The most efficient fluorescent tubes are the T5. With a smaller diameter (16mm) than earlier tubes, these can achieve a luminous efficacy of up to 104lm/W


4- Discharge lamps:


Discharge lamps work by striking an electrical arc between two electrodes, causing a filler gas to give off light.

Different metals and filler gasses can be used to provide a range of colour and brightness.

Discharge lamps provide high luminous efficacy combined with long life, resulting in the most economical light source available


Types of gas-discharge lamps:The gas discharge lamps have three types as follows:

A- Low pressure discharge lamps:

Low-pressure lamps have working pressure much less than atmospheric pressure. For example common fluorescent lamps operate at a pressure of about 0.3% of atmospheric pressure.

- Compact fluorescent lamp,

- Fluorescent lamps,

- Low pressure sodium lamps: the most efficient gas-discharge lamp type, producing up to 200 lumens per watt, but at the expense of very poor color rendering. The almost monochromatic yellow light is only acceptable for street lighting and similar applications.

BUILDING | SERVICES | TWO (BLD60503)B- High pressure discharge lamps:

High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure. For example, a high pressure sodium lamp has an arc tube under 100 to 200 torr pressure, about 14% to 28% of atmospheric pressure; some automotive HID headlamps have up to 50 bar or fifty times atmospheric pressure.

- Metal halide lamps: These lamps produce almost white light, and attain 100 lumen per watt light output. Applications include indoor lighting of high buildings, parking lots, shops, sport terrains.

- High pressure sodium lamps: producing up to 150 lumens per watt. These lamps produce a broader light spectrum than the low pressure sodium lamps. Also used for street lighting, and for artificial photoassimilation for growing plants

- High pressure mercury-vapor lamps: This lamp type is the oldest high pressure lamp type, being replaced in most applications by the metal halide lamp and the high pressure sodium lamp.


•C- High-intensity discharge lamps:

A high-intensity discharge (HID) lamp is a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. Compared to other lamp types, relatively high arc power exists for the arc length. Examples of HID lamps include: Mercury-vapor lamps.•Metal halide lamps.•Ceramic discharge metal halide lamps.•Sodium vapor lamps.•Xenon arc lamps.•Ultra-High Performance (UHP).

HID lamps are typically used when high levels of light and energy efficiency are desired.


5- Light Emitting Diode (LED):

LEDs use semi-conductors to convert electrical energy directly into light. They are only recently becoming available as a light source for lighting purposes, and are highly efficient and long lasting.

LED torches are becoming very popular, as they provide a far longer battery life than other types of light source.


1.Second: Forms of Artificial lighting:

There are two forms for Artificial lighting as follows:

1.Indoor lighting 2.Outdoor lighting


1- Indoor lighting:

Indoor lighting is usually accomplished using light fixtures, and is a key part of interior design, these light fixtures or light luminaires can be defined as follows:

Luminaire is a device that distributes filters or transforms the light emitted from one or more lamps.

The luminaire includes all the parts necessary for fixing and protecting the lamps, except the lamps themselves.

In some cases, luminaires also include the necessary circuit auxiliaries, together with the means for connecting them to the electric supply.

The basic physical principles used in optical luminaire are reflection, absorption, transmission and refraction.


1.Types of Indoor Light fixtures/luminaires:

Light fixtures/luminaires are classified according to the following:

1.The light function. 2.Lamp type. 3.Installation method. 4.The percentage of light output above and below the horizontal.


1- Types of Light fixtures according to light function:

There are five basic types of light fixtures according to the function or aim of using it as follows:

Ambient (general lighting).•Task.•Accent.•Informational lighting/Guidance Lighting.•Decorative lighting.


A- Ambient lighting Ambient lighting provides an area with overall illumination. Also known as general lighting, it radiates a comfortable level of brightness without glare and allows you to see and walk about safely.

Ambient lighting is often provided by traditional pendant type fixtures, down lights, chandeliers, or ceiling mounted fixtures etc.

The general decor and aspect of the room will affect the amount of general lighting required. Having a central source of ambient light in all rooms is fundamental to a good lighting plan


B- Task lighting

Task lighting, or directional lighting, is aimed at a specific task; It is a way to provide more light on a specific area to perform a task that requires more light than the ambient fixtures can give. It can be provided by recessed and track lighting, pendant lighting and undercabinet lighting, as well as by portable floor and desk lamps.

Task lighting should be free of distracting glare and shadows and should be bright enough to prevent eye strain.


C- Accent lighting Accent lighting is also a sort of a directional lighting that adds drama to a place by creating visual interest. As part of an interior design scheme, it is used to draw the eye to houseplants, paintings, sculptures and other prized possessions. It can also be used to highlight the texture of a brick or stone wall, window treatments or outdoor landscaping.

To be effective, accent lighting requires as least three times as much light on the focal point as the general lighting surrounding it.

Accent lighting is usually provided by recessed and track lighting or wall-mounted picture lights


D- Informational lighting (Guidance Lighting)

It is designed to help us see our way safely. The light in your closet, the light by your doorbell, and night lights, as well as path lighting and motion lights, are all good examples of informational lighting. The photo to the right is a typical night light with a photo sensor. Informational lighting can be beautiful as well as functional, and can create dramatic statements. Lights inset on stairs can create pathways that enhance architecture, while outdoor informational lighting can create


E- Decorative lighting

Light strips, pendants, chandeliers, and sconces are all examples of light fixtures that draw attention to themselves and add character to the place being lighted. Many are also used for general lighting.


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BS 2 5 electrical installatition

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