Air Conditioning System Configurations - Electrical Knowhow
Air Conditioning System Configurations - Electrical Knowhow
Air Conditioning System Configurations - Electrical Knowhow
Conditioning System Configurations ~ Electrical Knowhow
Air Conditioning System Configurations
I explained the different types of the Heating systems and today I will begin explaining the
Air Conditioning Systems as follows.
You can review the previous topic, “Electrical Load Classification and Types” for more information and
good following.
The air‐conditioning components and equipments may be designed and assembled in hundred different ways
but in practice these are broadly classified into three categories:
1‐ Decentralized Systems (Individual Room Systems): This can be divided to three major types as follows:
2‐ Semi‐ centralized systems (packaged systems): This can be divided to two major types as follows:
3‐ Centralized systems (Central Hydronic systems): This can be divided to three major types as follows:
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The following table will show a comparison between these configurations as follows:
These are systems in which heating and cooling is conducted locally, these systems are relatively common in
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schools, small hotels, domestic applications, residential homes and small offices.
Decentralized Systems are essentially direct expansion (DX) systems, which operate using direct expansion
of refrigerant in the finned tubes across the air path.
In smaller buildings, smaller room air conditioners are less expensive to operate than central units, even
though their efficiency is generally lower than that of central air conditioners.
The split systems are individual systems in which the two heat exchangers are separated (one outside, one
inside). The split air conditioner can be installed in rooms and offices where you don’t want to disturb the
setup of the room and avoid demolitions in your favorite space.
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There are two main parts of the split air conditioner. These are:
1) Outdoor unit:
This unit is installed outside the room or office space which is to be cooled and houses important
components of the air conditioner like:
The compressor:
External power has to be supplied to the compressor, which is utilized for compressing the refrigerant and
increases its pressure before sending it to the condenser. The size of the compressor varies depending on
the desired air conditioning load. In most of the domestic split air conditioners hermetically sealed type of
compressor is used. In such compressors the motor used for driving the shaft is located inside the sealed
unit and it is not visible externally.
Condenser coil:
It is the coiled copper tubing with one or more rows depending on the size of the air conditioning unit and
the compressor. The condenser is also covered with the aluminum fins so that the heat from the refrigerant
can be removed at more faster rate.
Expansion Valve:
The expansion valve is usually a copper capillary tubing with several rounds of coils.The high pressure and
medium temperature refrigerant leaves the condenser and enters the expansion valve, where its
temperature and pressure drops suddenly.
2) Indoor unit:
The most common type of the indoor unit is the wall mounted type though other types like ceiling mounted
and floor mounted are also used. the indoor unit produces the cooling effect inside the room or the office
and houses
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Louvers or Fins:
The cool air supplied by the blower is passed into the room through louvers. The louvers help changing the
angle or direction in which the air needs to be supplied into the room as per the requirements.
There are two types of louvers: horizontal and vertical. The horizontal louvers are connected to a small
motor and their position can set by the remote control and the vertical louvers are operated manually and
one can easily change their position as per the requirements
Air filter:
It removes all the dirt particles from the room air and helps supplying clean air to the room. The air filter in
the wall mounted type of the indoor unit is placed just before the cooling coil.
Operation Method:
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, 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.
Controls:
Note: 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.
B‐ Window Units
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A window unit produces cool air on one side and rejects hot air on the other and provides
delivery of conditioned air to a room without ducts.
A window unit has a low initial cost and is quick and easy to install.
A window unit requires outside exposure for heat rejection and cannot be used for interior
rooms
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A cooling only system cools the indoor air but a heat pump provides cooling in summer season
and heating in winter season.
DX system operating in reverse vapor compression cycle is classified as Heat pump. Through an
addition of a special four‐way reversing valve, heat flow in mechanical refrigeration loop can be
reversed so that heat is extracted from outside air and rejected into the building.
Such a facility is required during winter season to heat the indoor using the same physical
components. Due to added heat of compression, the efficiency of heat pump is higher compared
to the cooling cycle.
A supplementary electric resistance heater may also be used to assist the heat pump at lower
outdoor temperatures. In colder climates, heats pumps require defrost period. During defrost
times the electric heater is the only means of heating the interior of the building.
Split heat pumps are Air‐to‐Air types and they are the most common type of heat pumps. It is
particularly suitable for factory‐built unitary heat pumps, and has been widely used for
residential and commercial application. Air is used as the heat source and heat sink. Extended
surface, forced convection heat transfer coils are normally employed to transfer the heat
between the air and the refrigerant. When selecting or designing an air‐source heat pump, two
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In the next Topic, I will explain other types of air conditioning systems configurations " Semi‐ centralized
systems and centralized systems air condition". so, please keep following.
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