UNIT12

E3106/12/16

ELECTRICAL MACHINERY & CONTROL                           

UNIT 12

 

AIR CONDITIONING (PART I)

 

 

 

             

                            OBJECTIVES

 

 

 

GENERAL OBJECTIVE

 

To know the concept of air conditioning

 

 

SPECIFIC OBJECTIVES

             

At the end of this unit, you would be able to:

• name the term of air conditioning
• state types of domestic air conditioning
• list the types of gas used in air conditioning unit
• recall the IEE rules

 

 

 

 

 

                            INPUT

 

 

 

12. INTRODUCTION

 

ir conditioning is important in daily life. Most people have little appreciation

of the basic principles of air conditioning, probably because the public in general only became conscious of air conditioning around 1920s. It was at this

time that the large-scale use of air conditioning in trains and theaters began.

 

It was these systems that first exposed large numbers of people to the comfort and advantages of summer cooling and at the same time caused erroneous impression that air conditioning is synonymous with cooling. The two primary reasons for using air conditioning are to improve the control of an industrial process and to maintain human comfort.

 

In this chapter we will discuss the types of domestic air conditioning and gases used in air conditioning system. We will also learn about the Institute Electrical Engineering (IEE) rules.

 

 

 

 

 

 

 

 

12.1              DEFINITION OF AIR CONDITIONING

 

 

The definition of the term air conditioning is simultaneous mechanical control of temperature, humidity, air purity and air motion. Unless all of these conditions are under control, there is no need of applying air conditioning in any system or equipment. Air conditioning is the process of extracting the warm and dirty atmosphere from enclosed areas such as rooms, offices, factories, hospitals, etc., cooling and cleaning it, and returning it to these areas. It combines the use of air filters, normally water washed with a refrigeration plant.

 

 

2. TYPES OF DOMESTIC AIR CONDITIONING

 

Air conditioning systems are generally classified as being either central unit systems or unitary system.

 

1. Central Unit Systems

 

In central unit system ( Figure 12.1), the part such as compressor, condenser, evaporators and expansion valve is placed in one close location, however the cooling tower is located outside of it . Cool air is piped out from evaporators in air monitoring room to the space to be air conditioned. This system is used at hotels, shopping complex and big building.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 12.1: Central unit system

 

2. Unitary System

 

In this system, factory assembled air conditioners are installed in or adjacent to the space to be conditioned. The unitary air conditioning systems are either self-contained system such as window units and packed units, or remote split systems.

Figure 12.2: Cut away of self contained system

(Source: Refrigeration & Conditioning Technology; William C. Whitman

& William M. Johnson)

 

1. Self-contained System

 

Self-contained systems have all of the components

installed on one base, Figure 12.2, with the possible

exception of the condenser. Water-cooled systems

have a water tower placed at some location outside

the building with the water piped to the condenser.

 

Air-cooled systems may be installed on an outside

wall with the necessary provisions made to allow

the condenser air to circulate outdoors freely (see Figure 12.3). Self-contained system can be divided into window units and packed units.

 

 

Figure 12.3: Self-contained condenser connection 

(Source: Refrigeration & Conditioning Technology; William C. Whitman & William M. Johnson)

 

 

 

Page 512 (figure 19.47 Self-contained condenser connections)

 

 

 

 

 

 

 

 

• Window Units

Figure 12.4: Window units

This unit is assembled at window or wall hole. Condenser is contained with air from fan. All components window unit state in cabinet, see

Figure 12.4.This unit are used to contain small

spaces such as bedroom and small room office.

 

 

 

• Packed Units

(a) Water cooled

(b) Air cooled

Figure 12.5: Packed unit

Packed units can be used with condenser air cooled or water cooled (Figure 12.5). Packed units are usually used in the medium space office.

 

 

 

 

 

 

 

 

 

 

3. Remote Split Systems

 

These systems are in more common use in the residential and small commercial installations. They have the evaporator, blower and furnace located in a closet in an equipment room with condensing unit, we can see at Figure 12.6.

Figure 12.6: Remote split system

(Source: Refrigeration & Conditioning Technology; William C. Whitman & William M. Johnson)

 

             

The refrigerant is piped from the condensing unit to the indoor coil through copper tubing. The air is ducted from the air conditioning equipment to the space to be

              conditioned. Most residential units have the                            indoor section centrally located within the space, which eliminates the               need for a return air duct system. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

             

 

 

 

Test your UNDERSTANDING before you continue to the next input

ACTIVITY 12A

 

 

 

 

 

 

12.1              What are the two primary reasons for using air conditioning?

 

2. What is the definition of the term air conditioning?

 

3. What are the two classifications of air conditioning?

 

4. What are the differences between central unit system and unitary system?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FEEDBACK TO ACTIVITY 12 A

 

 

 

12.1              The two primary reasons for using air conditioning are to improve the control of an industrial process and to maintain human comfort.

 

12.2              The definition of the term air conditioning is the simultaneous mechanical control of temperature, humidity, air purity and air motion. Air conditioning is the process of extracting the warm and dirty atmosphere from enclosed areas such as rooms, offices, factories, hospitals, etc., cooling and cleaning it, and returning it to these areas.

 

3. The two classifications of air conditioning types are central unit system and unitary system.

 

4. The differences between central unit systems and unitary systems are :

Central Unit System	Unitary System
- The part such as compressor, condenser, evaporators and expansion valve is placed in one close location except cooling tower. - Air cooling is piped from evaporators at control room air to the space to be conditioned.	- The unitary air conditioning systems are following two types either self-contained system such as windows units and packed units, and remote split systems - Self-contained systems have all of the components installed on one base. - Remote split system have the evaporator, blower and furnace all located in a closet in an equipment room with condensing unit.

 

 

                            INPUT

 

 

 

3. TYPES OF GAS IN AIR CONDITIONING SYSTEM

 

Coolant is a liquid used in air conditioning system to produce a cooler by eliminating heat from air. Most coolant is in gas or vapor form at certain temperature and atmospheric pressure. For example the substances are Freon-11, Freon-12, Freon-22 and Ammonia.

 

1. Freon-11

Freon-11 boils at 23.70C. This substance is used in industrial air conditioning system which use centrifugal compressor.

 

2. Freon-12

Freon-12 or R-12 boils at 300C. Coolant is used in industries, home, water coolant, refrigerator and others. Freon-12 is used in air conditioning system. This system uses a sieving or rotate compressor. It can be classified as a non hazardous gas.

 

3. Freon-22

Freon-22 or R-22 boils -40.70C. Freon-22 is used as coolant for industrial air conditioning system, window unit, package conditioning unit and others. Freon-22 can be classified as a non hazardous gas.

 

4. Ammonia

Ammonia is a coolant used in the absorption conditioning system. The gas has no colour, flammable, poisonous, and can be water dissolved. It boils at normal pressure -330C.

 

4. INSTITUTE OF ELECTRICAL ENGINEERING (IEE) LAWS

 

When working on air conditioning units, it is important to remember that the conditioned air must contain enough oxygen to sustain life. Working on a complete air conditioning system involves many of the dangers involved in refrigeration systems and heating systems (see Table 12.1).

Table 12.1: IEE Laws

Always wear goggles when working with refrigerant in these systems Always wear goggles around ductwork to prevent cutting the hands and fingers. Provide protective shields around operating motors and fans. Be sure that the electric power is off before servicing electrical components Keeps hand, feet and clothing clears of belts, fans, and rotating parts. Use only safe ladders when working on the roofs of buildings Never carry equipment, tools or supplies up or down a ladder. Transport these items with a rope of buildings. Avoid contact with electric circuits when the area around the equipment is wet. Do not leave loose, light objects on a roof during high winds.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Test your UNDERSTANDING before you continue to the next input

ACTIVITY 12 B
 

 

 

 

 

 

 

12.5              Fill in the blanks with the correct answers

__________ is a liquid is used in air conditioning system to produce a cooler with throw it the ________ from air. Most coolant state in ______ or vapor at temperature and ___________ pressure.

 

12.6              State the differences between Freon-11, Freon-12 and Freon-22

 

12.7              List the IEE rules

             

 

 

 

 

 

 

 

 

 

 

 

FEEDBACK TO ACTIVITY 12 B

 

 

 

12.5              Coolant is a liquid is used in air conditioning system to produce a cooler with throw it the heat from air. Most coolant state in gas or vapor at temperature and atmospheric pressure.

 

12.6             

Freon-11	Freon-12	Freon-22
- boils at 23.70C.   - This substance is used in industrial air conditioning system where using centrifugal compressor.	- Freon-12 or R-12 boils at 300C. - using sieving or rotate compressor	- Freon-22 or R-22 boils at -40.70C. - Freon-22 is used as coolant for industrial air conditioning system, window unit, package conditioning unit and others.

 

 

7. Refer the note 12.4

 

 

 

 

 

 

 

SELF-ASSESMENT

 

 

 

If you face any problem, discuss it with your lecturer

You are approaching success. TRY all the questions ini this self-assessment section and check your answers with those given in the feedback on Self-Assessment given on the next page. 

 

 

Question 12-1

 

A.              How does the air conditioning system condition the space?

 

Question 12-2

 

A.              Complete the diagram below.

 

Question 12-3

 

A.              Where do we normally use window units and packed units?

 

B.              State the differences between self-contained system and remote split system.

 

 

Question 12-4

 

A.              With the guidance from your lecturer:

1. Identify the types of air conditioning system at your polytechnic, government office, shopping complex and home.
2. Study the air conditioning system of a car. Sketch and list down the components.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FEEDBACK TO SELF-ASSESMENT

 

 

 

Question 12-1

 

The air conditioning system can condition the space with extracting the warm and dirty atmosphere from enclosed areas such as rooms, offices, factories, hospitals, etc., cooling and cleaning it, and returning it to these areas. Also, in air conditioning system produce a cooler with throw it the heat from air.

 

Question 12-2

 

A.

 

 

 

 

 

 

 

Question 12-3

 

A.              Window units - this unit are used for to be contained the small space such as bedroom and small room office.

              Packed units - usually used at the medium space office

 

B.             

Self-contained system

Remote split system

- All of the components installed on one base, with the possible exception of the condenser.   - Water-cooled systems have a water tower placed at some location outside the building with the water piped to the condenser.   - Air-cooled systems may be installed on an outside wall with the necessary provisions made to allow the condenser air to circulate outdoors freely.

- They have the evaporator, blower and furnace all located in a closet in an equipment room with condensing unit.   - The refrigerant is piped from the condensing unit to the indoor coil through copper tubing.     - The air is ducted from the air conditioning equipment to the space to be               conditioned. Most residential units have the                            indoor section centrally located within the space, which eliminates the               need for a return air duct system.

 

 

Question 12-4

 

A.              Refer to your lecturer