SPLIT SYSTEM
Most often when dealing with air conditioners we come across the term "split system".
A split system is an air conditioning unit consisting of two main parts - the external and internal unit.
The compressor and condenser are located in the external unit, while the evaporator is in the internal unit.
The external and internal unit are connected via insulated copper pipes which contain the operating substance - freon.
FUNCTIONING OF AN AIR-CONDITIONER
The cooling effect is achieved via the circulation of the operating substance in the so-called left-direction cycle.
The liquid operating substance enters the evaporator located in the internal unit and evaporates when it passes through the pipes. Heat is necessary for the evaporation process. The operating substance takes the heat from the air in the room. That way the air is cooled via passing through the inverter. After the operating substance has evaporated, it goes in a gaseous state through the pipe line to the compressor in the external unit. Through compression the pressure and temperature of the operating matter rise and in that state it enters the condenser, which is also located in the external unit, where it transforms into liquid again. Through the condensation process heat is generated. Outside air takes over the heat by passing over the condenser and warms up that way. Liquid operating matter goes from the condenser to the thermoexpansion valve in which its pressure and temperature drop. It then as such enters the evaporator and the whole procedure is repeated.
The evaporator and the condenser are heat exchangers made up of copper pipes, in which the operating substance flows, connected with aluminum laminas that increase the exchanging surface and consequently the quantity of exchanged heat.
Air flow over the evaporator and condenser is greatly facilitated by fans located next to them. In the internal unit a tangential fan is situated next to the evaporator, and next to the condenser in the external unit there is an axial fan.
An air-conditioner can also heat air inside the room, and the heating effect is gained by the right-direction cycle. In that case the evaporator in the internal unit becomes the condenser while the condenser in the external unit becomes the evaporator. The air from the room is heated when passing through the internal unit because it uses the condensation heat, and the environmental air cools.
Direction of the process (operating matter) can be altered with a four-way valve which enables the operating matter to circulate in both directions.
PARTS OF AN AIR-CONDITIONER
- EXTERNAL UNIT – compressor, operating substance tank, condenser, axial fan, thermoexpansion valve, case
- INTERNAL UNIT – evaporator, tangent fan, filter, case
DIVISION OF AIR-CONDITIONERS
- purpose
- appliances for domestic use - apartments, houses
- appliances for commercial use – offices, shops, cafes...
- number of internal units
- single system – one internal and one external unit
- multi system
- dual – 2 internal and 1 external unit
- trial – 3 internal and 1 external unit
- quadral - 4 internal and 1 external unit
- type of internal unit
- wall
- duct
- cassette
- floor ceiling
CAPACITY
Cooling effect - refrigerant effect of an air-conditioner, expressed mostly in kW, but often also in BTU/h (1 BTU/h=0,293 W).
Cooling capacity is based on room temperature 27°C/19°C (its own thermometer) and outside temperature 35°C.
Heating effect of an air-conditioner is expressed mostly in kW, but also often in BTU/h (1 BTU/h=0,293W).
Heating capacity is based on room temperature 21°C and outside temperature 7°C/6°C (its own thermometer).
Most frequent models on our market:
| Cooling effect |
kW |
2,1 |
2,6 |
3,5 |
5,3 |
7,0 |
| |
BTU/h |
7000 |
9000 |
12000 |
18000 |
24000 |
| Heating effect |
kW |
2,5 |
3,2 |
3,8 |
5,6 |
7,9 |
| |
BTU/h |
8500 |
11000 |
13000 |
19000 |
29000 |
Calculator for choosing a suitable air-conditioner
BINDING POWER OF THE APPLIANCE
Binding power of the appliance, that is rated effect.
Cosumption of electric power when cooling or heating is expressed in kW.
ENERGY CLASS/CATEGORY
Energy class – classification of air-conditioners by energetic efficiency.
There are 7 classes of energetic efficiency, from A (the best) to G (the worst).
Energetic efficiency is the ratio between spent electric energy and gained effect.
EER – ratio between spent electric energy and gained COOLING effect.
COP – ratio between spent electric energy and gained HEATING effect.
The bigger the EER/COP, the more refrigerant/heating energy you get for 1kW/h of invested electric energy.
AIR FLOW
The air flow of an air-conditioner is expressed in m3/h. It can be indicated as rated or depending on fan speed - minimal-rated-maximum.
NOISE LEVEL
Noise level is expressed in dB(A), and is indicated for both external and internal units.
POWER SUPPLY
Power supply characteristics - voltage, frequency and phase number are expressed in 230V-50Hz-1 (or 3), depending on whether the device is one- or three-phase.
DIMENSIONS AND WEIGHT
Dimensions are indicated for both external and internal unit (length, width and height of the appliance in mm), whereas mass is expressed in kg.
WORKING MEDIUM
In commercial air-conditioning ecological gases are used as refrigerants, fluorohydrocarbon HFC, which do not contain chlorine that damages the ozone layer, are not flammable nor toxic.
The most common gases in air-conditioners are R407C and R410A.
Freons are gases used as refrigerants in the cooling technology. They are organic fluorine and chlorine derivates if methane and ethane.They have been used since 1930, at the time R12 i R22 were the most known. Freons' attributes that started their mass consumption is their non-flammability, non-toxicity and their lack of taste and smell. Until then the most common refrigerants were poisonous ammonia and methyl chloride. The consumption of such substances was limited by the Montreal protocol after it was proven that releasing these substances into the atmosphere results in damaging the ozone layer and global warming.
By the beginning of 2006, when the "Regulation/Act about substances that damage the ozone layer" was put into effect, appliances which contain hydrochlorofluorocarbons HCFC (R22), which are proven to damage the ozone layer, could be imported.
When the installation or servicing of an air-conditioner is done by a non-professional, the operating substance may be released into the atmosphere, which is no longer allowed. This can be avoided by controlling the air-conditioner regularly, examining freon installations and keeping record, replacing the operating matter with ona that does not damage the ozone layer, training maintenance workers for dealing with air-conditioners, collecting and storage of the used refrigerant.
There are four centers in Croatia that collect freon. They are located in Split, Rijeka, Osijek and Split.
This is why air-conditioners can only be installed by companies authorized by MZOPUG.
ALTERNATIVE OPERATING SUBSTANCES IN AIR-CONDITIONERS
An organic blend of two or more fluids which can be separated through destillation. An important characteristic of theirs is that the evaporation or condensation temperature with constant pressure is not always the same. Other thermodynamic features, such as heat transition coefficient, are worse than those of the previously used R22, which leads to decreased cooling effect.
R404 A is a zeotropic blend of R125, R143 and R134a, ratio 44/52/4%.
R407C is a blend of R125, R32 and R134a, ratio 25/23/52%.
REGULATION OF AN AIR-CONDITIONER
The effect of an air-conditioner can be regulated on/off or by inverter regulation.
On/off regulation – the compressor of the air-conditioner works or does not work depending on whether the set temperature on the air-conditioner is achieved. This causes frequent switching on and off of the device (compressor), which results in increased consumption of electric energy.
Inverter regulation – the compressor of the air conditioner has a frequency regulation of revolution number, which enables regulating effect. By regulating effect more precise regulation of room temperature is facilitated, and wanted room temperature is achieved much faster so the consumption of electric energy decreases, even by 30 %.