Lesson 6: HVAC Part 3 - Air Conditioning Systems

Air Conditioning System

A mechanical system designed to remove heat from an indoor space and reject it to the outside, in order to control temperature, humidity, and air quality and provide thermal comfort for occupants.

Air Conditioning

is primarily a heat-removal process, not air generation or ventilation.

Air Conditioning System

cools and conditions indoor air by transferring heat from inside a building to the outside, rather than by "creating cold."

Vapor-Compression Refrigeration Cycle

removes heat from an indoor space by circulating refrigerant through evaporation, compression, condensation, and expansion processes in a closed loop.

Refrigerant

A chemical compound capable of transitioning from liquid to gas and back again

Evaporator - Heat Absorption (Cooling Stage)

What happens:

• Low-pressure, low-temperature liquid refrigerant enters the evaporator

• It absorbs heat from indoor air

• The refrigerant evaporates (boils) into a vapor

Evaporator - Heat Absorption (Cooling Stage)

Result:

• Indoor air becomes cooler

• Refrigerant leaves as a low-pressure vapor

refrigerant

Inside the building, a cold fluid called ________ flows through the evaporator and absorbs heat from the indoor air, which makes the room feel cooler.

Compressor - Pressure & Temperature Increase

What happens:

• Low-pressure vapor enters the compressor

• The compressor squeezes the vapor

• Pressure and temperature increase significantly

Compressor - Pressure & Temperature Increase

Result:

• Refrigerant becomes a high-pressure, high-temperature vapor

compressor

As the refrigerant absorbs heat, it turns into a gas and is sent to the _______, where it is squeezed and heated up.

Condenser - Heat Rejection (Outdoor Stage)

What happens:

• Hot, high-pressure vapor enters the condenser

• Heat is released to outdoor air or water

• Refrigerant condenses into a liquid

Condenser - Heat Rejection (Outdoor Stage)

Result:

• Heat removed from the building is rejected outside

• Refrigerant becomes a high-pressure liquid

condenser

The hot gas then moves to the the _______ located outside the building, where the heat is released to the outdoor air, which is why the outdoor unit feels warm.

Expansion Device - Pressure & Temperature Drop

What happens:

• High-pressure liquid passes through the expansion device

• Pressure suddenly drops

• Temperature drops accordingly

Expansion Device - Pressure & Temperature Drop

Result:

• Refrigerant becomes a low-pressure, low-temperature liquid

• Ready to absorb heat again in the evaporator

expansion device

After releasing heat, the refrigerant turns back into a liquid and passes through a small opening called the ________, where its pressure and temperature drop, making it cold again.

Evaporator

Fan Coil Unit (Indoor Unit) also known as

Fan Coil Unit (Indoor Unit)

Cools and circulates air inside the conditioned space

Air-Condensing Unit (Outdoor Unit)

Rejects heat to the outside

Air-Condensing Unit (Outdoor Unit)

Contains the compressor, condenser and condenser fan

Refrigerant Piping

Connects FCU and ACU

Drainage System

Removes condensate from indoor unit

Motor (Compressor and Fans)

Provide mechanical power to run the compressor and drive the fans that move air across the coils.

Blower (Indoor Fan)

Pushes indoor air through the evaporator coil and distributes cooled air into the room.

Condenser Fan

Blows outdoor air across the condenser coil to help release heat from the refrigerant.

Evaporator coil

Absorbs heat from indoor air

Condenser coil

Releases heat to the outdoor environment

Thermostat

Senses indoor temperature and controls when the AC system turns on, off, or adjusts cooling levels.

Window-Type Air Conditioning System

A single, self-contained unit where all components are housed in one casing and installed through a window or wall opening to cool a single room.

Window-Type Air Conditioning System

Simple but noisy and less efficient

1.0-1.5 m

Window-Type Air Conditioning System recommended mounting height: ____-___ m above floor level

Split-Type Air Conditioning System

An air-conditioning system with two separate units: an indoor unit that cools the room and an outdoor unit that releases heat.

Split-Type Air Conditioning System

Quieter and more efficient

Split-Type Air Conditioning System

Most common system due to quiet indoor operation and efficiency

Split-Type Air Conditioning System

Components:

• FCU (indoor)

• ACU (outdoor)

Split-type air-conditioning systems

_____________ have manufacturer-specified limits for piping length and height difference between the FCU and ACU to ensure efficient refrigerant flow, proper oil return, and reliable system operation.

3.0-15.0 m

Split-Type Air Conditioning System horizontal distance (piping length)

5.0-7.0 m

Split-Type Air Conditioning System vertical distance (height difference)

Multi-Split System

A system where multiple indoor units OPER are connected to one outdoor unit, allowing several rooms to be cooled while reducing the number of outdoor units required.

Multi-Split System

Components:

• Multiple FCUs (indoor)

• One ACU (outdoor)

Multi-Split System

Saves façade and exterior space

80.0 m max

Multi-Split System total piping length (all indoor units combined)

3.0 m

Multi-Split System M=minimum piping length: _____m per indoor unit

25.0 m max

Multi-Split System distance per indoor unit from the outdoor unit

15 meters

Multi-Split System vertical distance (height difference):
Outdoor unit above indoor units

10 meters

Multi-Split System vertical distance (height difference):
Outdoor unit below indoor units

Packaged Air Conditioning Unit (PACU)

A large, self-contained air-conditioning unit that distributes cooled air through ducts to serve large spaces.

Packaged Air Conditioning Unit (PACU)

All components in one cabinet

Packaged Air Conditioning Unit (PACU)

Ducted supply and return air

Packaged Air Conditioning Unit (PACU)

Roof-mounted or ground-mounted

Packaged Air Conditioning Unit (PACU)

Commonly used in commercial buildings, malls, and hotels

600-900 mm

Packaged Air Conditioning Unit (PACU) ceiling utility space requirement for the ductworks

Packaged Terminal Air Conditioner (PTAC)

A single packaged unit installed through a wall.

Packaged Terminal Air Conditioner (PTAC)

One unit per room

Packaged Terminal Air Conditioner (PTAC)

Wall-mounted, usually below windows

Packaged Terminal Air Conditioner (PTAC)

Individual room control

Centralized Air Conditioning System

A large-scale system that cools an entire building using a central plant and distributes cooling through air handling units or fan coil units.

Centralized Air Conditioning System

Serves entire building

Centralized Air Conditioning System

Most suitable for very large cooling loads and continuous operation

Chiller

One of the main components of the Centralized Air Conditioning System that produces chilled water

Air Handling Unit (AHU)

One of the main components of the Centralized Air Conditioning System that handles large amounts of air, especially fresh air, for many spaces

Fan Coil Unit (FCU)

One of the main components of the Centralized Air Conditioning System that cools individual rooms or small zones, usually using recirculated air

Air Handling Unit (AHU)

are typically provided per floor or large zone to handle fresh air and large air volumes

Fan Coil Unit (FCU)

are provided per room or small space for individual temperature control; both may be used together in centralized systems.

Centralized Air Conditioning System

Placement:

• Chillers in plant room or rooftop

• AHUs in mechanical rooms

• FCUs in ceilings with 450-600 mm utility space

Variable Refrigerant Flow (VRF)

A multi-zone air-conditioning system that varies refrigerant flow to multiple indoor units to provide efficient, independent cooling for different rooms.

Variable Refrigerant Flow (VRF)

Variable refrigerant flow based on demand

Variable Refrigerant Flow (VRF)

Independent zone control

Variable Refrigerant Flow (VRF)

Ideal for offices, hotels, and mixed-use buildings where different rooms require different cooling levels

Variable Refrigerant Flow (VRF)

Components:

• Multiple FCUs (indoor)

• Large ACUs (outdoor)

2.2-2.7 m

Variable Refrigerant Flow (VRF) recommended FCU mounting height

300.0 m or more

Variable Refrigerant Flow (VRF) horizontal Distance (Piping Length)

90 m

Variable Refrigerant Flow (VRF) vertical Distance (Height Difference)

Inverter Air Conditioners

Air conditioners that use variable-speed compressors, allowing the unit to adjust cooling output based on demand.

Inverter Air Conditioners

Compressor speed varies with cooling demand

Inverter Air Conditioners

More energy-efficient

Inverter Air Conditioners

Stable indoor temperature

Inverter Air Conditioners

Lower operating cost

0.75 HP

Floor Area: 10-15 sqm
Recommended AC Capacity?

1.0 HP

Floor Area: 16-20sqm
Recommended AC Capacity?

1.5 HP

Floor Area: 21-25 sqm
Recommended AC Capacity?

2.0 HP

Floor Area: 26-36 sqm
Recommended AC Capacity?

2.5 HP

Floor Area: 36-45 sqm
Recommended AC Capacity?

3.0 HP

Floor Area: 46-60 sqm
Recommended AC Capacity?