What is meant by the terms COP and EER? |
| The terms COP (coefficient of performance) and EER (energy efficiency ratio) describe the heating and cooling efficiency of air conditioners. They indicate the ratio of heating or cooling provided by a unit relative to the amount of electrical input required to generate it. |
The refrigerant cycle: what is it? |
An air conditioner works similar to a refrigerator. The refrigerant flows through the system, and changes in state or condition. There are four processes in the 'refrigeration cycle'.
1 The compressor which pumps the refrigerant around the system, is the heart of the air conditioner. Before the compressor, the refrigerant is a gas at low pressure. Because of the compressor, the gas becomes high pressure, gets heated and flows towards the condenser. 2 At the condenser, the high temperature, high pressure gas releases its heat to the outdoor air and becomes subcooled high pressure liquid. 3 The high pressure liquid goes through the expansion valve, which reduces the pressure, and thus temperature goes below the temperature of the refrigerated space. This results in cold, low pressure refrigerant liquid. 4 The low pressure refrigerant flows to the evaporator where it absorbs heat from the indoor air throught evaporation and becomes low pressure gas. The gas flows back to the compressor where the cycle starts all over again. |
What are the influences on the capacity need? |
| Throughout the ages, we have sought to improve the level of comfort offered by our surroundings. In colder regions, we have tried to heat our dwellings and in warmer climates, to cool them down because if we are not comfortable, we can neither work nor relax. But thermal comfort vital to our well being, is subject to three basic influences: The human factor -
our clothing and activity level and how long we remain in the same situation, Our space -
radiation temperature and surrounding temperature,
The air -
its temperature, velocity and humidity. |
What is heat transfer? |
Heat always flows from a warmer substance to a cooler one. In reality, the faster moving molecules transfer some of their energy to slower ones. Thus the faster molecules slow down a little and the slower ones speed up. Expressed simply, this means that when it is hot outside, the heat attemps to 'invade' colder interior spaces.
Heat can be transferred from one body to another by any of the following methods, radiation, conduction and convection. |
What is inverter technology? |
The inverter technology is integrated in the outdoor unit. The inverter technology can be compared to the technology in a car: " The harder you push your accelerator, the faster you go." An inverter unit will gradually increase its capacity based on the capacity needed in the room to cool down or heat up the room. The non-inverter can be compared with switching on or off a lamp. Switching on this type of unit will start to run on full load. |
What is sound pressure/sound power? |
Sound pressure level (Lp) -
Is a measure of the sound energy emitted from a source of noise, expresses in decibel or dBA Sound power level (Lw)
Is the same as Lp but measured in predefined conditions.
The sound power level is independant on: the location of the equipment, the environmental, conditions, and the distance from the measurement point. |
What is a heat pump? |
| A heat pump extracts low temperature energy from the environment and increases its temperature for heating purposes. Heat pump efficiencies are normally quoted as the coefficient of performance of the system, these are typically in the range 3 to 5. In other words, extracting heat from renewable sources requires just 1kW of electrical input in order to generate 3kW to 5kW of heating output. Heat pump systems therefore, are 3 to 5 times more efficient than fossil fuel boilers and are more than capable of warming a house completely, even during the lowest winter temperatures. The increasing popularity of these heating systems is reflected by their overwhelmingly successful application in the cold climates of Scandinavia. |
|
What is the difference between sensible and latent heat? |
Sensible heat - When an object is heated, its temperature rises as heat is added. The increase in heat is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat removed is also called sensible heat. Heat that causes a change in temperature in an object is called sensible heat.
Latent heat - All pure substances in nature are able to change their state. Solids can become liquids (ice to water) and liquids can become gases (water to vapor) but changes such as these require the addition or removal of heat. The heat that causes these changes is called latent heat.
Latent heat however, does not affect the temperature of a substance - for example, water remains at 100°C while boiling. The heat added to keep the water boiling is latent heat. Heat that causes a change of state with no change in temperature is called latent heat.
Appreciating this difference is fundamental to understanding why refrigerant is used in cooling systems. It also explains why the terms 'total capacity' (sensible & latent heat) and 'sensible capacity' are used to define a unit's cooling capacity. During the cooling cycling, condensation forms within the unit due to the removal of latent heat from the air. Sensible capacity is the capacity required to lower the temperature and latent capacity is the capacity to remove the moisture from the air. |
The outdoor unit discharges water or steam? |
| The defrost operation activated in the heating mode removes frost, which turns into water or steam. A small amount of water is also discharged during a heating operation. |
The air conditioner does not blow air immediately after it starts operation in the heating mode? |
The air conditioner conducts a "warm-up" operation first so that it won't blow cold air in the heating mode. The fan starts operating after one to four minutes of warm-up operation.
(The warm-up operation becomes longer when the outside air temperature is low). |
The air conditioner produces an air releasing sound? |
| The air releasing sound is caused by a change of the refrigerant flow direction. This sound is generated when the air conditioner stops operating or the defrosting operation is activated in a heating operation. |
The air conditioner stops operation (Operation lamp remains lit)? |
| When power supply voltage fluctuates largely, the air conditioner may stop operating to protect the equipment. (When power supply returns to a normal condition, the air conditioner resumes operation after three minutes.) |
The air conditioning produces a crackling sound?
|
| Plastic parts such as the front panel produces a crackling sound when they expand or contract slightly due to temperature change. |
Can air conditioning systems make people ill? |
| Only an ill maintained air conditioning system can make you ill. A well maintained air conditioning system can only contribute to a healthier environment. |
Will the air con installation cause cold draughts? |
| Cold draughts are sometimes associated with air conditioning and indeed, this can be caused by incorrectly conceived systems. The likely effect on personnel resulting from the location of the indoor unit and its air distribution pattern must therefore be considered at the design stage. |
What is legionella and is it a danger to us? |
The legionella bacteria is a natural inhabitant of water. Temperature is of great importance for the legionella proliferation. Especially temperatures between 40 and 50°C may lead to colonization of the bacteria.
If a cold water air conditioning system is installed then there is no harm to humans. In chilled water systems for industrial purpose, the legionella bacteria can not live because of the low temperature of the water in the closed circuit. |
|