building service chapter 5

PSMZA Course Note (Chapter 5)

Ver. 1 (MSH-Jun2013): CC608 Building Services 1

5.1 AIR CINDITIONING (A/C) SYSTEM 5.1 The Basic Principle of Air Conditioning

Air conditioning is the process whereby the condition of air, as defined by its temperature and moisture content, is changed. Note that in practice other factors must also be taken into account especially cleanliness; odour; velocity & distribution pattern.

5.1.1 Human Comfort

Inevitably 'comfort' is a very subjective matter. The Engineer aims to ensure 'comfort' for most people found from statistical surveys. Most people (90%) are comfortable when the air temperature is between 18-22°C and the %sat is between 40-65%. This zone can be shown on the psychometric chart and is known as the “comfort zone”.

Outside air is quite likely to be at a different condition from the required comfort zone condition. In order to bring its condition to within the comfort zone we may need to do one or more of the following:- heat it; cool it; dehumidify it; humidify it; or mix it.

When people or animals are present in buildings, ventilation air is necessary to dilute odours and limit the concentration of carbon dioxide and airborne pollutants such as dust, smoke and volatile organic compounds (VOCs).

Ventilation air is often delivered to spaces by mechanical systems which may also heat, cool, humidify and dehumidify the space. Air movement into buildings can occur due to uncontrolled infiltration of outside air through the building fabric (see stack effect) or the use of deliberate natural ventilation strategies. Advanced air filtration and treatment processes such as scrubbing, can provide ventilation air by cleaning and recirculating a proportion of the air inside a building.

5.1.2 Types of Ventilation

i. Mechanical or forced ventilation: through an air handling unit or direct injection to a space by a fan. A local exhaust fan can enhance infiltration or natural ventilation, thus increasing the ventilation air flow rate.

ii. Natural ventilation occurs: when the air in a space is changed with outdoor air without the use of mechanical systems, such as a fan. Most often natural ventilation is assured through operable windows but it can also be achieved through temperature and pressure differences between spaces. Open windows or vents are not a good choice for ventilating a basement or other below ground structure. Allowing outside air into a cooler below ground space will cause problems with humidity and condensation.

iii. Mixed mode ventilation or hybrid ventilation: utilises both mechanical and natural ventilation processes. The mechanical and natural components may be used in conjunction with each other or separately at different times of day. The natural component, sometimes subject to unpredictable external weather conditions may not always be adequate to ventilate the desired space. The mechanical component is then used to increase the overall ventilation rate so that the desired internal conditions are met. Alternatively the mechanical component may be used as a control measure to regulate the natural ventilation process, for example, to restrict the air change rate during periods of high wind speeds.

Figure 5.1: Thermal comfortable zone



iv. Infiltration: is separate from ventilation, but is often used to provide ventilation air.

5.2 The Basic Principle of Air Conditioning System

The principle of this system must be referring to the heat transfer at the two medium. Heat is a form of energy. Every object on earth has some heat energy. The less heat an object has, the colder we say it is.

Cooling is the process of transferring heat from one object to another. When an air-

conditioning system cools, it is actually removing heat and transferring it somewhere else. This can be demonstrated by turning on a spot cooler and placing one hand in front of the cold air nozzle and the other over the warm air exhaust. You will feel the action of the transfer of heat. Air conditioning system is a one of mechanical ventilation part. The system by which air conditioners provide cooling is called the refrigerant cycle.

5.2.1 How Does Air Conditioning Work

As with all air conditioning systems the principle remains the same whereby the heat is removed from one area and replaced with chilled dry air and the hot air is expelled, normally to the outside atmosphere. As you can see from this typical example of a air conditioning system, the ambient air is drawn over the condenser that can best described as a ‘radiator’ as seen on motor vehicles but instead of water running through the system it contains a refrigerant gas.

On its journey around the system it has three main stages; the evaporator contains the

sub-cooled refrigerant and air blows through its veins to release the chilled dry air into the room, the condenser contains the high temperature gas that once again air is blown through the veins collecting the heat as it passes through and this is then expelled outside.

5.2.2 Basic Operations

An air conditioner is able to cool a building because it removes heat from the indoor air and transfers it outdoors. A chemical refrigerant in the system absorbs the unwanted heat and pumps it through a system of piping to the outside coil. The fan, located in the outside unit, blows outside air over the hot coil, transferring heat from the refrigerant to the outdoor air.

Figure 5.2: Ventilation by ducting



Most air conditioning systems have five mechanical components: i. A compressor ii. A condenser iii. An evaporator coil iv. Blower v. A chemical refrigerant

Most central air conditioning units operate by means of a split system. That is, they

consist of a ‘hot’ side, or the condensing unit - including the condensing coil, the compressor and the fan-which is situated outside your home, and a ‘cold’ side that is located inside your home. The cold side consists of an expansion valve and a cold coil, and it is usually part of your furnace or some type of air handler. The furnace blows air through an evaporator coil, which cools the air. Then this cool air is routed throughout your home by means of a series of air ducts. A window unit operates on the same principal, the only difference being that both the hot side and the cold side are located within the same housing unit.

The compressor (which is controlled by the thermostat) is the ‘heart’ of the system. The

compressor acts as the pump, causing the refrigerant to flow through the system. Its job is to draw in a low-pressure, low-temperature, refrigerant in a gaseous state and by compressing this gas, raise the pressure and temperature of the refrigerant. This high-pressure, high-temperature gas then flows to the condenser coil.

The condenser coil is a series of piping with a fan that draws outside air across the coil.

As the refrigerant passes through the condenser coil and the cooler outside air passes across the coil, the air absorbs heat from the refrigerant which causes the refrigerant to condense from a gas to a liquid state. The high-pressure, high-temperature liquid then reaches the expansion valve.

The evaporator coil is a series of piping connected to a furnace or air handler that blows

indoor air across it, causing the coil to absorb heat from the air. The cooled air is then delivered to the house through ducting. The refrigerant then flows back to the compressor where the cycle starts over again.

5.2.3 Air Conditioner Filters

The most important maintenance task that will ensure the efficiency of your air conditioner is to routinely replace or clean its filters. Clogged, dirty filters block normal airflow and reduce a system’s efficiency significantly. With normal airflow obstructed, air that bypasses the filter may carry dirt directly into the evaporator coil and impair the coil’s heat-absorbing capacity. Filters are located somewhere along the return duct’s length. Common filter locations are in walls, ceilings, furnaces, or in the air conditioner itself.

Some types of filters are reusable; others must be replaced. They are available in a

variety of types and efficiencies. Clean or replace your air conditioning system’s filter or filters every month or two during the cooling season. Filters may need more frequent attention if the air conditioner is in constant use, is subjected to dusty conditions, or you have fur-bearing pets in the house. If you use a disposable type filter, it’s always wise to keep several spares inside the house.

Below are some commonly used terms in the heating, ventilation and air conditioning

industry. These may be useful when dealing with contractors or assessing a solution to your problem.

5.2.4 Air Conditioning Cycle

Mechanical refrigeration is accomplished by continuously circulating, evaporating, and condensing a fixed supply of refrigerant in a closed system. Evaporation occurs at a low temperature and low pressure while condensation occurs at a high temperature and high pressure. Thus, it is possible to transfer heat from an area of low temperature (i.e., refrigerator cabinet) to an area of high temperature (i.e., kitchen).



Figure 5.3: Air conditioning cycle



Referring to the illustration at figure 5.3. i. Beginning the cycle at the evaporator inlet (1), the low-pressure liquid expands,

absorbs heat, and evaporates, changing to a low-pressure gas at the evaporator outlet (2).

ii. The compressor (4) pumps this gas from the evaporator through the accumulator (3), increases its pressure, and discharges the high-pressure gas to the condenser (5).

iii. The accumulator is designed to protect the compressor by preventing slugs of liquid

refrigerant from passing directly into the compressor. An accumulator should be included on all systems subjected to varying load conditions or frequent compressor cycling. In the condenser, heat is removed from the gas, which then condenses and becomes a high-pressure liquid.

iv. In some systems, this high-pressure liquid drains from the condenser into a liquid

storage or receiver tank (6). On other systems, both the receiver and the liquid line valve (7) are omitted.

v. A heat exchanger (8) between the liquid line and the suction line is also an optional

item, which may or may not be included in a given system design.

vi. Between the condenser and the evaporator an expansion device (10) is located. Immediately preceding this device is a liquid line strainer/drier (9), which prevents plugging of the valve or tube by retaining scale, dirt, and moisture.

vii. The flow of refrigerant into the evaporator is controlled by the pressure differential

across the expansion device or, in the case of a thermal expansion valve, by the degree of superheat of the suction gas. Thus, the thermal expansion valve shown requires a sensor bulb located at the evaporator outlet. In any case, the flow of refrigerant into the evaporator normally increases as the evaporator load increases.

viii. As the high-pressure liquid refrigerant enters the evaporator, it is subjected to a much

lower pressure due to the suction of the compressor and the pressure drop across the expansion device. Thus, the refrigerant tends to expand and evaporate. In order to evaporate, the liquid must absorb heat from the air passing over the evaporator.

ix. Eventually, the desired air temperature is reached and the thermostat or cold control

(11) will break the electrical circuit to the compressor motor and stop the compressor.

x. As the temperature of the air through the evaporator rises, the thermostat or cold control remakes the electrical circuit. The compressor starts, and the cycle continues.

xi. In addition to the accumulator, a compressor crankcase heater (12) is included on

many systems. This heater prevents accumulation of refrigerant in the compressor crankcase during the non-operating periods and prevents liquid slugging or oil pump out on start-up.

xii. Additional protection to the compressor and system is afforded by a high- and low-

pressure cut-out (13). This control is set to stop the compressor in the event that the system pressures rise above or fall below the design operating range.

Other controls not indicated on the basic cycle which may be part of a system include:

evaporator pressure regulators, hot gas bypass regulators, electric solenoid valves, suction pressure regulators, condenser pressure regulators, low-side or high-side float refrigerant controllers, oil separators, etc.

It is extremely important to analyze completely every system and understand the intended

function of each component before attempting to determine the cause of a malfunction or failure.



5.3 Types of Air Conditioning System The choice of which air conditioner system to use depends upon a number of factors

including how large the area is to be cooled, the total heat generated inside the enclosed area, etc. An HVAC designer would consider all the related parameters and suggest the system most suitable for your space. Commonly home and office were used windows unit, split unit, cassette unit, tower unit and cube air conditioner.

Figure 5.4: Standard home air condition part



5.3.1 Window Air Conditioner

Window air conditioner is the most commonly used air conditioner for single rooms. In this air conditioner all the components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a single box. This unit is fitted in a slot made in the wall of the room, or more commonly a window sill.

These types of AC are designed to be fitted in window sills. A single unit of Window Air Conditioner houses all the necessary components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil enclosed in a single box. Since a window AC is a single unit, it takes less effort to install as well as for maintenance. The advantages:

i. Single unit air conditioner ii. Less effort needed for installation iii. Costs lesser in comparison to other varieties

5.3.2 Split Air Conditioner

The split air conditioner comprises of two parts: the outdoor unit and the indoor unit. The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve.

The indoor unit comprises the evaporator or cooling coil and the cooling fan. For this unit

you don’t have to make any slot in the wall of the room. Further, present day split units have aesthetic appeal and do not take up as much space as a window unit. A split air conditioner can be used to cool one or two rooms. The advantages:

i. Internal unit takes up less space for installation ii. Usually more silent than window ACs iii. Minimally affect your home décor iv. Can be installed in room with no windows

Split air conditioners are used for small rooms and halls, usually in places where window

air conditioners cannot be installed. However, these days many people prefer split air conditioner units even for places where window air conditioners can be fitted. The split air conditioner takes up a very small space of your room, looks aesthetically cool and makes very little noise, ensuring sound sleep for you when you return from your day’s hard work.

Figure 5.5: Window unit type



There are two main parts of the split air conditioner. These are: i. Outdoor unit

This unit houses important components of the air conditioner like the compressor, condenser coil and also the expansion coil or capillary tubing. This unit is installed outside the room or office space which is to be cooled. The compressor is the maximum noise making part of the air conditioner, and since in the split air conditioner, it is located outside the room, the major source of noise is eliminated. In the outdoor unit there is a fan that blows air over the condenser thus cooling the compressed Freon gas in it. This gas passes through the expansion coil and gets converted into low pressure, low temperature partial gas and partial liquid Freon fluid.

ii. Indoor unit

It is the indoor unit that produces the cooling effect inside the room or the office. This is a beautiful looking tall unit usually white in color, though these days a number of stylish models of the indoor unit are being launched. The indoor unit houses the evaporator coil or the cooling coil, a long blower and the filter. After passing from the expansion coil, the chilled freon fluid enters the cooling coil. The blower sucks the hot, humid and filtered air from the room and it blows it over the cooling coil. As the air passes over cooling coil its temperature reduces drastically and also loses the excess moisture. The cool and dry air enters the room and maintains comfortable conditions of around 25-27 degree celsius as per the requirements.

The temperature inside the space can be maintained by thermostat setting. The setting should be such that comfortable conditions are maintained inside the room, and there is also chance for the compressor to trip at regular intervals. If the compressor keeps running continuously without break, its life will reduce. These days multi-split air conditioners are also being used commonly. In units for one outdoor unit there are two indoor units which can be placed in two different rooms or at two different locations inside a large room.

Since there is long distance between the indoor and the outdoor unit, there is always loss of some cooling effect; hence for the same tonnage, split air conditioners produce somewhat less cooling effect than window air conditioners. However, with modern insulation material this gap has been reducing between the two. In any case, there are number of instances where there is just no alternative to the split air conditioners.



5.3.3 Packaged Air Conditioner

An HVAC designer will suggest this type of air conditioner if you want to cool more than two rooms or a larger space at your home or office. There are two possible arrangements with the package unit. In the first one, all the components, namely the compressor, condenser (which can be air cooled or water cooled), expansion valve and evaporator are housed in a single box.

The cooled air is thrown by the high capacity blower, and it flows through the ducts laid

through various rooms. In the second arrangement, the compressor and condenser are housed in one casing. The compressed gas passes through individual units, comprised of the expansion valve and cooling coil, located in various rooms.

Figure 5.6: Split unit type



Figure 5.8: Package unit type without cooled condenser

Figure 5.7: Package unit with water cooled condenser



5.3.4 Central Air Conditioner Central air conditioning is used for cooling big buildings, houses, offices, entire hotels,

gyms, movie theatres, factories etc. If the whole building is to be air conditioned, HVAC engineers find that putting individual units in each of the rooms is very expensive making this a better option. A central air conditioning system is comprised of a huge compressor that has the capacity to produce hundreds of tons of air conditioning. Cooling big halls, malls, huge spaces, and galleries is usually only feasible with central conditioning units. See also clause 5.4.

5.4 Principle of the Cooling Substance - Central Air Conditioning Plants

Central air conditioning plants are used for applications like big hotels, large buildings having multiple floors, hospitals, where very high cooling loads are required. The article describes various possible arrangements of central air conditioning plants.

The central air conditioning plants or the systems are used when large buildings, hotels,

theatres, airports, shopping malls, are to be air conditioned completely. The window and split air conditioners are used for single rooms or small office spaces. If the whole building is to be cooled it is not economically viable to put window or split air conditioner in each and every room. Further, these small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc.

In the central air conditioning systems there is a plant room where large compressor, condenser, thermostatic expansion valve and the evaporator are kept in the large plant room. They perform all the functions as usual similar to a typical refrigeration system. However, all these parts are larger in size and have higher capacities. The compressor is of open reciprocating type with multiple cylinders and is cooled by the water just like the automobile engine. The compressor and the condenser are of shell and tube type. While in the small air conditioning system capillary is used as the expansion valve, in the central air conditioning systems thermostatic expansion valve is used.

The chilled is passed via the ducts to all the rooms, halls and other spaces that are to be

air conditioned. Thus in all the rooms there is only the duct passing the chilled air and there are no individual cooling coils, and other parts of the refrigeration system in the rooms. What is we get in each room is the completely silent and highly effective air conditions system in the room. Further, the amount of chilled air that is needed in the room can be controlled by the openings depending on the total heat load inside the room.

The central air conditioning systems are highly sophisticated applications of the air

conditioning systems and many a times they tend to be complicated. It is due to this reason that there are very few companies in the world that specialize in these systems. In the modern era of computerization a number of additional electronic utilities have been added to the central. There are two types of central air conditioning plants or systems:

i. Direct expansion or DX central air conditioning plant ii. Chilled water central air conditioning plant



5.4.1 Direct Expansion or DX Central Air Conditioning Plant In this system the huge compressor and the condenser are housed in the plant room,

while the expansion valve and the evaporator or the cooling coil and the air handling unit are housed in separate room. The cooling coil is fixed in the air handling unit, which also has large blower housed in it. The blower sucks the hot return air from the room via ducts and blows it over the cooling coil. The cooled air is then supplied through various ducts and into the spaces which are to be cooled. This type of system is useful for small buildings.

i. The Plant Room

The plant room comprises of the important parts of the refrigeration system, the compressor and the condenser. The compressor can be either semi-hermetically sealed or open type. The semi-hermetically sealed compressors are cooled by the air, which is blown by the fan, while open type compressor is water cooled. The open compressor can be driven directly by motor shaft by coupling or by the belt via pulley arrangement.

The condenser is of shell and tube type and is cooled by the water. The

refrigerant flows along the tube side of the condenser and water along the shell side, which enables faster cooling of the refrigerant. The water used for cooling the compressor and the condenser is cooled in the cooling tower kept at the top of the plant room, though it can be kept at other convenient location also.

ii. The Air Handling Unit (AHU) Room The refrigerant leaving the condenser in the plant room enters the thermostatic

expansion valve and then the air handling unit, which is kept in the separate room. The air handling unit is a large box type of unit that comprises of the evaporator or the cooling coil, air filter and the large blower. After leaving the thermostatic expansion valve the refrigerant enters the cooling coil where it cools the air that enters the room to be air conditioned. The evaporator in the air handling unit of the DX central air conditioning system is of coil type covered with the fins to increasing the heat transfer efficiency from the refrigerant to the air.

There are two types of ducts connected to the air handling unit: for absorbing the

hot return air from the rooms and for sending the chilled air to the rooms to be air conditioned. The blower of the air handling unit enables absorbing the hot return air that has absorbed the heat from the room via the ducts. This air is then passed through the filters and then over the cooling coil. The blower then passes the chilled air through ducts to the rooms that are to be air conditioned.

The DX expansion system runs more efficiently at higher loads. Even in case of

the breakdown of the plants, the other plants can be used for the cooling purpose. The DX types of central air conditioner plants are less popular than the chilled water type of central conditioning plants.

iii. Air Conditioned Room

This is the space that is to be actually cooled. It can be residential room, room of the hotel, part of the office or any other suitable application. The ducts from the air handling room are passed to all the rooms that are to be cooled. The ducts are connected to the grills or diffusers that supply the chilled air to the room. The air absorbs the heat and gets heated and it passes through another set of the grill and into the return air duct that ends into the air handling unit room. This air is then re-circulated by the air handling unit.

Though the efficiency of the DX plants is higher, the air handling units and the

refrigerant piping cannot be kept at very long distance since there will be lots of drop in pressure of the refrigerant along the way and there will also be cooling losses. Further, for the long piping, large amounts of refrigerant will be needed which makes the system very expensive and also prone to the ma instance problems like the leakage of the refrigerant.



Due to these reasons the DX type central air conditioning systems are used for

small air conditioning systems of about 5 to 15 tons in small buildings or the number of rooms on a single floor. If there are large air conditioning loads, then multiple direct expansion systems can be installed. In such cases, when there is lesser heat load one of the plants can be shut down and the other can run at full load.

The DX expansion system runs more efficiently at higher loads. Even in case of

the breakdown of the plants, the other plants can be used for the cooling purpose. The DX types of central air conditioning plants are less popular than the chilled water type of central conditioning plants.

Figure 5.9: Central air conditioning plant



5.4.2 Chilled Water Central Air Conditioning Plant

This type of system is more useful for large buildings comprising of a number of floors. It has the plant room where all the important units like the compressor, condenser, throttling valve and the evaporator are housed. The evaporator is a shell and tube. On the tube side the Freon fluid passes at extremely low temperature, while on the shell side the brine solution is passed. After passing through the evaporator, the brine solution gets chilled and is pumped to the various air handling units installed at different floors of the building.

The air handling units comprise the cooling coil through which the chilled brine flows, and

the blower. The blower sucks hot return air from the room via ducts and blows it over the cooling coil. The cool air is then supplied to the space to be cooled through the ducts. The brine solution which has absorbed the room heat comes back to the evaporator, gets chilled and is again pumped back to the air handling unit.

To operate and maintain central air conditioning systems you need to have good

operators, technicians and engineers. Proper preventative and breakdown maintenance of these plants is vital.

The chilled water types of central air conditioning plants are installed in the place where

whole large buildings, shopping mall, airport, hotel, comprising of several floors are to be air conditioned. While in the direct expansion type of central air conditioning plants, refrigerant is directly used to cool the room air; in the chilled water plants the refrigerant first chills the water, which in turn chills the room air.

Cooling Tower

Figure 5.10: Chilled Water Central Air Conditioning Plant



In chilled water plants, the ordinary water or brine solution is chilled to very low

temperatures of about 6 to 8 degree Celsius by the refrigeration plant. This chilled water is pumped to various floors of the building and its different parts. In each of these parts the air handling units are installed, which comprise of the cooling coil, blower and the ducts. The chilled water flows through the cooling coil. The blower absorbs return air from the air conditioned rooms that are to be cooled via the ducts. This air passes over the cooling coil and gets cooled and is then passed to the air conditioned space.

All the important parts of the chilled water air conditioning plant are shown in the above

figure and described in detail below:

i. Central Air Conditioning Plant Room The plant room comprises of all the important components of the chilled water air

conditioning plant. These include the compressor, condenser, thermostatic expansion valve and the evaporator or the chiller. The compressor is of open type and can be driven by the motor directly or by the belt via pulley arrangement connected to the motor. It is cooled by the water just like the automotive engine.

The condenser and the evaporator are of shell and tube type. The condenser is

cooled by the water, with water flowing along the shell side and refrigerant along the tube side.The thermostatic expansion valve is operated automatically by the solenoid valve.

The evaporator is also called as the chiller, because it chills the water. If the

water flows along the shell side and refrigerant on the tube side, it is called as the dry expansion type of chiller. If the water flows along tube side and the refrigerant along the shell side, it is called as the flooded chiller. The water chilled in the chiller is pumped to various parts of the building that are to be air conditioned. It enters the air handling unit, cools the air in cooling coil, absorbs the heat and returns back to the plant room to get chilled again. The amount of water passing into the chiller is controlled by the flow switch.

In the central air conditioning plant room all the components, the compressor,

condenser, thermostatic expansion valve, and the chiller are assembled in the structural steel framework making a complete compact refrigeration plant, known as the chiller package. Piping required to connect these parts is also enclosed in this unit making a highly compact central air conditioning plant.

The air handling units are installed in the various parts of the building that are to be air conditioned, in the place called air handling unit rooms. The air handling units comprise of the cooling coil, air filter, the blower and the supply and return air ducts. The chilled water flows through the cooling coil. The blower absorbs the return hot air from the air conditioned space and blows it over the cooling coil thus cooling the air. This cooled air passes over the air filter and is passed by the supply air ducts into the space which is to be air conditioned. The air handling unit and the ducts passing through it are insulated to reduce the loss of the cooling effect.

ii. Air Handling Unit (AHU) Rooms

The air handling units are installed in the various parts of the building that are to be air conditioned, in the place called air handling unit rooms. The air handling units comprise of the cooling coil, air filter, the blower and the supply and return air ducts. The chilled water flows through the cooling coil.

The blower absorbs the return hot air from the air conditioned space and blows it

over the cooling coil thus cooling the air. This cooled air passes over the air filter and is passed by the supply air ducts into the space which is to be air conditioned. The air handling unit and the ducts passing through it are insulated to reduce the loss of the cooling effect.



iii. Air Conditioned Rooms These are the rooms or spaces that are to be air conditioned. These can be

residential or hotel rooms, halls, shops, offices, complete theater, various parts of the airport etc. At the top of these rooms the supply and the return air ducts are laid. The supply air ducts supply the cool air to the room via one set of the diffusers, while the return air ducts absorbs the hot return air from the room by another set of the diffusers. The hot return air enters the air handling unit, gets cooled and again enters the room via supply duct to produce air conditioning effect.

iv. Cooling Tower

The cooling tower is used to cool the water that absorbs heat from the compressor and the condenser. When water flows through these components some water gets evaporated, to make up this loss some water is also added in the cooling tower. The cooling tower is of evaporative type. Here the water is cooled by the atmospheric air and is re-circulated through the compressor and the condenser.

5.4.3 Comparison of DX and Chilled Water Central Air Conditioning Plants

The Direct Expansion (DX) and Chilled Water central air conditioning plants are both used at different places depending on the applications and size of the place to be air conditioned. Both of them have their own advantages and disadvantages.

i. DX Central Air Conditioning Plants Are More Efficient

In the DX type of central air conditioning plants the air used for cooling the room is directly chilled by the refrigerant in the cooling coil of the air handling unit. Due to this heat transfer process is more efficient, since there is no middle agency involved for the heat transfer resulting in higher cooling efficiency.

In case of the chilled water system, the cooling effect from the refrigerant is first

transferred to the chilled water, which is then used to chill the air used for cooling the room. There is some loss of the cooling effect when it is being transferred from the refrigerant to the chilled water and from there to the air due to which the chilled water systems have lesser cooling efficiency. The chilled water acts as the secondary medium for cooling the room air in air handling unit.

Further, the chilled water has to flow long distance along the whole building. On its way it tends to get heated due to friction of flow and also due to surrounding heat absorption. The chilled water also has to be pumped by the pump, which adds more heat to it. Thus as the chilled water flows from the chiller to the air handling unit and again back to the chiller, apart from the heat from air, it also absorbs lots of additional heat, which leads to high increase in its temperature.

The chiller has to remove this additional heat from the water due to which its

efficiency decreases or rather additional power is required to remove this additional heat. In the DX type of central air conditioning plants the refrigerant travels only through the small distances and there is no pump involved so the additional heat absorption is less, which makes the DX plants even more efficient.



ii. The Chilled Water Plants Used For The Large Multi Storey Buildings In the direct expansion types of the central air conditioning plant, the refrigerant

like R22 flows through the whole air conditioning system including the air handling unit. When the refrigerant flows in the refrigeration piping there is lots of drop in its pressure. Due to this the length of the refrigeration tubing and the distance between the condenser and the air handling unit should be kept minimum possible.

If the air handling unit is kept at the height more than the condenser, the loss in

pressure is pronounced since refrigerant travelling from the condenser to the air handling unit is in liquid state. As the distance between the air handling unit and the condenser increases the loss in pressure also increases. At certain point the losses may be so high that the refrigerant may not be able to reach the air handling unit, leading to complete failure of the system. At the larger height difference there is also oil return problem from the refrigerant to the compressor.

Due to these reasons, in direct expansion type of the central air conditioning plant

there is limitation on the distance between the condenser and the air handling unit. The distance between the two cannot be too high. This limits the application of the direct expansion type of central air conditioning systems to the small buildings or a number of rooms on the single floor. In such cases the plant room and air handling room and the rooms to be cooled are located on the same floor. The height difference between the condenser and the air handling units has to be quite reasonable so that they can function well.

One of the solutions to increase the capacity of the DX systems can be to

increase the number of air handling units on upper floors. But with this will be additional number of joints in the refrigerant tubing from which there will be higher chances of leakage of highly expensive refrigerant. This leads to too many operational and maintenance problems.

One may think that we can employ compressor of very high capacity to increase

the refrigerant pressure, but this will lead to highly excessive capital and running costs of the plant. This is because we will have to install the compressor of capacity much higher than needed. Thus the direct expansion types of the air conditioning plants can be used only for smaller buildings or various rooms on the same floor.

There are no pressure loss problems in the chilled water system. In this system chilled water is pumped by the pump at very high pressure, which is good enough to carry it to various floors of the multi storey building. The losses in the pressure of water are accommodated by the sufficient capacity of the pump, which has low capital and running cost. Further, the water doesn’t carry any oil so there are no oil return problems.

In case of the chilled water system the compressor, condenser, expansion valve

and the chiller are all kept at the same level in the single plant room. There is no problem as such of the height difference between the condenser and the air handling unit since the refrigerant does not travels to the air handling unit. The flow of the refrigerant is limited to the chiller plant. The water chilled in the chilled flows to the various air handling units kept on different floors of the building.

The whole arrangement and the structure of the chilled water type of central air

conditioning plant makes it more suitable for cooling the large multi storey buildings and even for very long distances along the same floor level. This makes the chilled water central air conditioners more popular than the direct expansion type ones.



5.5 Factors for Choosing Air Conditioning Units The basic things for a man is food, cloth and house but now the summer seasons are too

long so mostly people require cooling and this requirement is fulfilled by air conditioning units which are available in market according to need and requirement of people.

To choose best air conditioning unit there are some factors to consider: i. Energy effectiveness: It means how much energy it takes while in working and this

is the most important thing to consider for consumers they don't afford too much billing. So take that conditioner which has Energy saving star ratings.

ii. Funds: This is the important thing while purchasing conditioner. That conditioner which not breaks budget and gives comfortable feel when at home or in office.

iii. Atmosphere: Always want that conditioner that is according to environment. Mostly portable air conditioning unit use CFC refrigerant but use chooses that one which filters all the air before entering into room.

iv. Vacant dish: Many people working for a long hours so they always want that appliance never have to empty. Don't want that appliance which fills your entire home with water when come back to home after working.

v. Automatic resume: Always buy that conditioner which have automatic restart option if room is too hot in summer and automatically adjust temperature according need.

vi. Portable unit: If living in a house i.e. on rent than portable conditioning is a great choice.

If portable air conditioning units were chosen, research needed on the features that are present in that, it is better to decide which type of air conditioner want because it is the basic necessity to relief in summer season. The portable air conditioning units are easy to maintain, clean, portable and can be taken wherever want. Before committing to a solution here are five important factors to consider when planning air conditioning design:

i. Budget For those looking to invest in an installation, it's important to get it right first time. There are plenty of options out there to suit budget, but do research on what to need first. Running costs should be considered as well as maintenance. And if don't choose the right one, a replacement can be costly to the business.

ii. Noise Whatever workplace, it's imperative that staff don't suffer from the unwanted distraction of a noisy air-con system. While all of them some sort of sound, it needn't be a problem if have an appropriately sized air conditioner and its location is well thought-out.

iii. Energy Consumption By ensuring have a supplier that designs project using CIBSE (Chartered Institution of Building Services Engineers) recommendations, its equipment capacity will be correctly calculated to provide with the most energy efficient air conditioning solution.

iv. Practicality Make sure choose a system that is easy to understand and that you feel comfortable using. Too many systems aren't used to their full capability because staff too nervous to press certain buttons due to not knowing what they do.

v. Future expansion It's vital to consider both current and future company needs when making decision. They will help design an effective long-term solution that can be added when business evolves. Commercial air conditioning can be of huge benefit to businesses, but before embarking on an air conditioning installation should seek the advice of a reputable supplier who can help make the right decisions about air conditioning design for organisation.



5.5.1 Air Treatment by Air Conditioner System The purpose of air retreatment is to adjust the supply air to the comfort needs of individual

rooms or room zones in a building. The overall goal is to optimize energy consumption. This goal is primarily achieved by providing only as much comfort as necessary, when and where it is used or requested. For example, there is no point maintaining comfort levels in office or hotel rooms when they are unoccupied.

The different heat gains in individual rooms or zones require individual adjustment of

heating or cooling output by varying either the temperature or flow volume of the supply air. How these adjustments are made by control means in common system types is explained in this chapter. These treatment were:

i. Humidity Control

Refrigeration air-conditioning equipment usually reduces the absolute humidity of the air processed by the system. The relatively cold (below the dew point) evaporator coil condenses water vapour from the processed air (much like an ice-cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapour from the cooled space and lowering the relative humidity in the room. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space. A specific type of air conditioner that is used only for dehumidifying is called a dehumidifier. Uncontrolled moisture indoors can cause major damage to the building structure, as well as to furnishings and to finish materials like floors, walls, and ceilings, otherwise can lead to health and performance problems for students and staff.

ii. Temperature Control Heating, ventilation and air conditioning (HVAC) systems control the temperature, humidity and quality of air in buildings to a set of chosen conditions. To achieve this, the systems need to transfer heat and moisture into and out of the air as well as control the level of air pollutants, either by directly removing them or by diluting them to acceptable levels. Heating systems increase the temperature in a space to compensate for heat losses between the internal space and outside. Otherwise an air temperature generally was controlled by heating and cooling process (as technically means the removal of heat, in contrast to heating, the addition of heat) the air.

iii. Clean Air Air-conditioning systems can promote the growth and spread of microorganisms, however, this is only prevalent in poorly-maintained water cooling towers. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided. Conversely, air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where an appropriate atmosphere is critical to patient safety and well-being. Air conditioning can have a negative effect on skin, drying it out, and can also cause dehydration. Air conditioning may have a positive effect on sufferers of allergies and asthma.

iv. Provide Air Ventilation and Air Movement Although a typical HVAC system has many controls, the control of outdoor air quantity that enters the building can have a significant impact on Indoor Air Quality (IAQ), yet typically is not part of standard practice. Demand controlled ventilation is addressed as a method of humidity control, but is not otherwise discussed here because its primary use is to reduce the supply of outdoor air below the recommended minimum for the purposes of saving energy, not for improving IAQ. Otherwise air motion refers to air velocity and to where the air distributed. It is controlled by appropriate air distribution equipment.



5.5.2 Differences With In Central and Split Unit Air Conditioning System

No. Item Central Unit Split Unit

1 Layout

2 Component

3 The system

4 Outside

unit More than 2 package unit: compressor,

condenser, fan Outdoor unit : compressor, condenser, fan

5 Inside Unit Cooling coil, Indoor blower, ceiling diffuser and ducting system used

Indoor unit: evaporator, blower, air filter

6 Space Large area to locates outside unit Small area need as well as suitable located

outdoor unit

7 Location Outside unit located on the ground and

inside unit in the roof/ceiling

Outdoor unit located at outside wall or floor and indoor unit place at a wall or ceiling in the

house

8 Cooling

area Suitable for large area and more room

to cool at the one time Suitable for single room and not loo large

area

9 Cost of

placement More expensive than a split unit type More cheaper than a central unit type

10 Electrical

power supply

Three phase power supply (415V) Can be choose one phase (240V) or three

phase (415V) depending a suitable

Table 5.1: Central and split unit comparison



5.6 Effects of Air Conditioning System to the Environment When examining the environmental impact of air conditioning and heat pump systems. It

has been shown repeatedly that the greatest contribution to global warming comes from the power it takes to run the system over its useful life.

Compares the contribution of the direct impact of the refrigerant due to leakage to the

impact due to the power the device consumes. The average contribution to the total global warming due to refrigerant leakage averages 3 to 4%. It also shows the benefit of increasing the efficiency of the system. A 20% increase in efficiency translates to a 12% decrease in total warming or more than three times the total direct effect of the refrigerant. In order to reduce the global warming influence of future air conditioning and heat pump systems increasing the energy efficiency of these systems will provide the greatest impact.

It was shown that using R-410A would allow for a more cost-effective approach when

designing high efficiency air conditioners and heat pumps. It would reduce the size increase of heat exchangers needed for high efficiency equipment. Optimized design will also reduce the required refrigerant charge by 25 to 30% thereby reducing the direct effect as well. Other leading choices such as hydrocarbons and CO2 make designing higher efficiency equipment more difficult.

Figure 5.11: No and used air conditioning heating

Figure 5.12: Heating situation



In the case of hydrocarbons, the need for a secondary loop or ether changes in the system necessary to reduce the risk of a highly flammable refrigerant use materials and there by cost that could be used to improve the efficiency of non-flammable refrigerant systems. Improvements are also needed in CO2 systems to make-up for the considerably lower thermodynamic efficiency of the cycle.

5.6.1 Environmental Impact

i. Energy Use The electricity generated to power air conditioning carries both global and personal health consequences. In burning fossil fuels such as coal to supply electricity to homes and workplaces, power plants discharge clouds of soot and other pollutants into the atmosphere. Among these are mercury and carbon dioxide (CO2). Air conditioner use in the U.S. results in an average of about 100 million tons of CO2 emissions from power plants every year.

ii. Pumping Out HCFCs Formerly used as cooling agents, ozone-depleting chlorofluorocarbons (CFCs) have been replaced by hydro-chloro-fluoro-carbons (HCFCs), which deplete 95% less ozone. However, booming demand for air conditioners in hot climates such as India and China has upped the chemical's output in developing countries 20 to 35% each year, causing damage at an alarming rate and possibly setting back ozone recovery by 25 years. In industrial countries, HCFCs are being replaced with ozone-safe cooling agents and will be banned in the U.S. by 2010. But HCFCs will be allowed in developing countries through 2040, and because they're still cheaper to use than ozone-safe chemicals, production in developing countries is expected to increase fivefold by 2010.

iii. Disposal

Federal law requires that HCFCs be recovered from air conditioners and other appliances before they are dismantled for recycling or tossed in landfills, and the EPA is authorized to impose fines of up to $25,000 for failure to comply with regulations. Before discarding your old unit, search for a company that is EPA-certified to recover HCFCs. Share the Air has certified companies listed by region.

iv. Raising the Local Temperature However, turning your air conditioning up also heats up the atmosphere outside in a much more literal way. The heat doesn’t just magically disappear – instead, that hot air didn’t want in our home or car is pumped outside, creating a mini heat zone. Add lots of these together, such as in a city centre, it’s have a full-blown urban heat island on our hands. This hot air rises quickly and forms small pockets, leading to abnormal weather patterns directly above the area.

Figure 5.13: Energy illustration



v. Personal Health In the midst of sweltering heat waves, air conditioning can be a lifesaver, protecting against heat stroke and hyperthermia. But, without proper maintenance, air conditioners can also be a health hazard. Dirty filters can allow allergens, pesticides and other particulate matter to enter your home from the outside, posing threats to indoor air quality. Exposure to those pollutants can trigger a host of health problems, including allergies and asthma and eye, nose and throat irritation.

vi. Global Warming

Scientists have spent decades figuring out what is causing global warming. They have looked at the natural cycles and events that are known to influence climate. But the amount and pattern of warming that's been measured can't be explained by these factors alone. The only way to explain the pattern is to include the effect of greenhouse gases (GHGs) emitted by humans. One of the first things scientists learned is that there are several greenhouse gases responsible for warming, and humans emit them in a variety of ways. Most come from the combustion of fossil fuels in cars, factories and electricity production. The gas responsible for the most warming is carbon dioxide, also called CO2. Other contributors include methane released from landfills and agriculture (especially from the digestive systems of grazing animals), nitrous oxide from fertilizers, gases used for refrigeration and industrial processes, and the loss of forests that would otherwise store CO2.

Some impacts from increasing temperatures are already happening:

a) Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice.

b) Sea level rise became faster over the last century. c) Some butterflies, foxes, and alpine plants have moved farther north or to higher,

cooler areas. d) Precipitation (rain and snowfall) has increased across the globe, on average.

Figure 5.15: Effect of global warming

Figure 5.14: Nature effect



Other effects could happen later this century, if warming continues: a) Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimeters)

by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimeters).

b) Hurricanes and other storms are likely to become stronger. c) Species that depend on one another may become out of sync. For example,

plants could bloom earlier than their pollinating insects become active. d) Floods and droughts will become more common. Rainfall in Ethiopia, where

droughts are already common, could decline by 10 percent over the next 50 years

5.6.2 Product of Environmental Friendly Air Condition

As climate change becomes an increasingly important concern, particularly for countries with major population centers to installing environmentally friendly air conditioners is vital. i. Check EER

When selecting an air conditioner, it’s important to consider its EER, or Energy Efficiency Rating (a scale of 1-6). Air conditioning products with high EER ratings are more efficient, and consume less energy, saving cost.

ii. Evaporative or Ducting The type of air conditioning chosen will also have an environmental impact. If in a dry heat climate, installing an evaporative air conditioner rather than a refrigerated or ducted system is a better environmental choice. However this is not an option in humid areas.

iii. Solar Air Conditioning

Solar air conditioning uses solar cells or photovoltaic panels located on the roof to power your air conditioner. Because the sun is strongest on the days where need cooling, this is a great concept. Not only will this reduce power bill, but when using less energy than what system is producing, the surplus energy will be fed back into the main power grid – for which a credit will be applied to next power bill.

iv. All Refrigerant Are Not Equal One concern that environmentalists have about air conditioners is that they contain refrigerants comprised of chemicals that are said to damage the environment. While impossible to remove all chemicals from air conditioning units, there are eco-friendly refrigerant options. If a unit that is less polluting you should look for one with R410a refrigerant or free CFC pollution.

v. Planning Good planning is key to completing a successful air conditioning project, starting with taking expert advice to determine the right type and size of unit is best. If pick a unit that’s too small, it will have to work harder to cool house, running up power bill and having a larger impact on the environment. By taking the time to adequately consider the environmentally friendly air conditioning options available, decision will not only impact the environment, but money as well.

Figure 5.16: Green air conditioning unit



5.7 Active Learning: How Much You Know About Global Warming



5.7.1 Active Learning: Answers



5.8 Glossary

Air Conditioner Assembly of equipment for the simultaneous control of air temperature, relative humidity, purity, and motion. Air Cooled Uses a fan to discharge heat from the condenser coil to the outdoors. Air-Source Air is being used as the heat source or heat sink for a heat pump. Ambient Temperature The temperature, usually of the air, that surrounds operating equipment. BTU (British Thermal Unit) The standard of measurement used for measuring the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit). BTUH The number of BTUs in an hour Central Air Conditioner System System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts. Compressor The pump that moves the refrigerant from the indoor evaporator to the outdoor condenser and back to the evaporator again. The compressor is often called ‘the heart of the system’ because it circulates the refrigerant through the loop. Condenser A device that transfers unwanted heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) that absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled condensers, water-cooled condensers, and evaporative condensers. The evaporative condenser uses a combination of air and water as its condensing medium. Most residential systems have an air-cooled condenser.

Condenser Coil A series or network of tubes filled with refrigerant, normally located outside the home, that removes heat from the hot, gaseous refrigerant so that the refrigerant becomes liquid again. Cooling Capacity A measure of the ability of a unit to remove heat from an enclosed space. COP Coefficient of Performance of a heat pump means the ratio of the rate of useful heat output delivered by the complete heat pump unit (exclusive of supplementary heating) to the corresponding rate of energy input, in consistent units and under operating conditions. DOE The Department of Energy. A government agency that sets industry efficiency standards and monitors the use of various energy sources. EER Energy Efficiency Ratio means the ratio of the cooling capacity of the air conditioner in British Thermal Units per hour, to the total electrical input in watts under ARI-specified test conditions.



Enthalpy Heat content or total heat, including both sensible and latent heat. The amount of heat contained in a refrigerant at any given temperature with reference to -40°F. Evaporator Absorbs heat from the surrounding air or liquid and moves it outside the refrigerated area by means of a refrigerant. It is also known as a cooling coil, blower coil, chilling unit or indoor coil. Evaporator Coil A series or network of tubes filled with refrigerant located inside the home that take heat and moisture out of indoor air as liquid refrigerant evaporates. Free Delivery There are no ducts and the unit may be installed in the field without ducts if needed. Ground-Source The ground or soil below the frost line is being used as the heat source or heat sink for a heat pump. Ground Water-Source Water from an underground well is being used as the heat source or heat sink for a heat pump. HVAC Heating, ventilation, and air conditioning. Heat Pump An air conditioner capable of heating by refrigeration. It may or may not include a capability for cooling. Outside air or water is used as a heat source or heat sink, depending upon whether the system is heating or cooling. Heating Capacity A measure of the ability of a unit to add heat to an enclosed space. HSPF Heating Seasonal Performance Factor means the total heating output of a heat pump in British Thermal Units during its normal usage period for heating divided by the total electrical energy input in watt-hours during the same period. Insulation Any material that slows down the transfer of heat. (K) Factor The insulating value of any material. Also known as conductivity. Kilowatt (kW) Equal to 1,000 watts. Kilowatt-hour (kWh) A common unit of electrical consumption measured by the total energy created by one kilowatt in one hour. Latent Heat The heat energy needed to change the state of a substance (i.e.: from a liquid to a gas) but not it’s temperature.



Sensible Heat Heat energy that causes a rise or fall in the temperature of a gas, liquid or solid when added or removed from that material. Sensible heat changes the temperature by changing the speed at which the molecules move. Single Package A central air conditioner which combines both condenser and air handling capabilities in a single packaged unit. Split System A central air conditioner consisting of two or more major components. The system usually consists of a compressor-containing unit and condenser, installed outside the building and a non-compressor -containing air handling unit installed within the building. This is the most common type of system installed in a home. Super-cooled Liquid Liquid refrigerant cooled below its saturation point. Sub-cooling Creating a drop in temperature by removing sensible heat from a refrigerant liquid. Superheated vapor Refrigerant vapor heated beyond its saturation point. Superheating Creating a rise in temperature by adding heat energy to a refrigeration vapor. Ton The unit of measurement for air conditioning system capacity. One ton of air conditioning removes 12,000 Btu’s of heat energy per hour from a home. Central air conditioners are sized in tons. Residential units usually range from 1 to 5 tons. Water-Source Water is being used as the heat source or heat sink for a heat pump. Sources of underground water are wells and sources of surface water are lakes, large ponds, and rivers. Watt A unit of power that equals one joule per second. Named after James Watt.



5.9 References

Books Egan M David (1986). The Building Fire Safety Concept. University Technology Malaysia,

Skudai. Fullerton R. L. (1979). Building Construction in Warm Climates. Volume 1, 2, 3. Oxford

University Press, United Kingdom. Hall F. (2000). Building Services & Equipment. Pearson Limited, England. MS EN 81-1:2012. Malaysian Standard. Safety Rules for the Construction and Installation of

Lift- Part1: electric Lifts (first revision). Department of Standards Malaysia. Nor Rizman (2010). Risk Assessment for Demolition Works In Malaysia. Faculy of Civil

Engineering and Earth Resources, Universiti Malaysia Pahang. Undergraduate thesis.

Prashant A/L Tharmarajan (2007(. The Essential Aspects of Fire Safety Management In Hihg-

Rise Buildings. University Teknologi Malaysia. Degree of master science thesis. Riger W. Haines, Douglas C. Hittle (2006). Control System for Heating, Ventilating and Air

Conditioning. Springer-Verlag, New York. Stein, Benjamin, Reynolds, John S., Grondzik, Walter T., and Alison G. Kwok, (2006).

Mechanical and Electrical Equipment for Buildings. 10th ed. Hoboken, New Jersey: John Wiley and Sons, Inc., 2006.

Tan, C. W. and Hiew, B.K., (2004), “Effective Management of Fire Safety in a High-Rise

Building”, Buletin Ingenieur vol. 204, 12-19. Journals N.H. Salleh and A.G. Ahmad. (2009). Fire Safety Management In Heritage Buildings: The

Current Scenario In Malaysia. CIPA Symposium Kyoto Japan. UIAM and USM. Code of Practices Approved Code Of Practice For Demolition: Health And Safety In Employment Act 1992.

Issued And Approved By The Minister Of Labour September 1994. Code of Practice for Lift Works and Escalator Works. (2002 ed). Code Of Practice For Demolition Of Buildings 2004. Published by the Building Department.

Printed by Taiwan Government Logistics Department. Code Of Practice For Demolition Of Buildings (2009). Malaysia Standard Supersede Ms 282

Part 1: 1975. Technical Committee For Construction Practices Under The Supervision Of Construction Industry Development Board, Malaysia.

Demolition Work Code Of Practice (July 2012). Australian Government. Work Health and Safety (Demolition Work Code of Practice) Approval 2012. Australian

Capital Territory. By Dr Chris Bourke, Minister for Industrial Relations.



Others Publishing Coby Frampton. Benchmarking World-class maintenance. CMC Charles Brooks Associates,

Inc. Electrical Installation and Systems (2006). Training Package UEE06. Industry Skills Council,

Australia. Fire Safety Manual (2002). Florida Atlantic University USA. Garis panduan Pendawaian Elektrik di bangunan Kediaman (2008). Suruhanjaya Tenaga

Malaysia. Jabatan Keselamatan Elektrik. Laws of Malaysia. Act 341: Fire Services Act 1988. Publish by The Commissioner Of Law

Revision, Malaysia Under The Authority Of The Revision Of Laws Act 1968 In Collaboration With Percetakan Nasional Malaysia Bhd 2006.

Operations & Maintenance Best Practices: A Guide to Achieving Operational Efficiency.

(August 2010). Release 3.0. Principles of Home Inspection: Air Conditioning and Heat Pumps. (2010). Educational Course

Note. Routine Maintenance Modules. Part II. Uniform Building By Law 1984. (1996). MDC Legal Advisers: MDC Publishers Printers Guidelines For Applicants For A Demolition Licence Issued Under The Occupational Safety

And Health Regulations 1996. Occupational Safety And Health Act 198. The Government of Commerce, Western Autralia.

Websites http://en.wikipedia.org/wiki/Electricity http://science.howstuffworks.com/electricity.htm http://en.wikipedia.org/wiki/Electricity_generation https://en.wikipedia.org/wiki/Fire_safety http://www.usfa.fema.gov/citizens/home_fire_prev/ https://en.wikipedia.org/wiki/Maintenance,_repair,_and_operations http://academia.edu/406774/Demolition_Work_in_Malaysia_The_Safety_Provisions http://www.mbam.org.my/mbam/doc/news/010-05Oct09-COP%20Demolition%20Works-corrected%20on%20%2030th%20sept%202009-1.doc http://en.wikipedia.org/wiki/Demolition http://www.safeworkaustralia.gov.au/sites/SWA/about/Publications/Documents/700/Demolition%20Work.pdf

http://en.wikipedia.org/wiki/Electricity

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http://www.usfa.fema.gov/citizens/home_fire_prev/

https://en.wikipedia.org/wiki/Maintenance,_repair,_and_operations

http://academia.edu/406774/Demolition_Work_in_Malaysia_The_Safety_Provisions

http://www.mbam.org.my/mbam/doc/news/010-05Oct09-COP%20Demolition%20Works-corrected%20on%20%2030th%20sept%202009-1.doc

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https://en.wikipedia.org/wiki/Air_conditioning http://www.nasa.gov/topics/earth/features/heat-island-sprawl.html http://www.projectnoah.org/education http://unfccc.int/files/methods_and_science/other_methodological_issues/interactions_with_ozone_layer/application/pdf/subgene.pdf http://www.cibse.org/Docs/barney2.doc http://en.wikibooks.org/wiki/Building_Services/Vertical_Transportation

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http://en.wikibooks.org/wiki/Building_Services/Vertical_Transportation

building service chapter 5

Engineering

condition of air

air temperature

outdoor air

air movement

ventilation air flow

natural ventilation

hybrid ventilation

types of ventilation