Personal Air-Conditions

Old ON/OFF and the New all DC Inverter 

A little bit of history in the discovery of personal air conditioning, the evolution of the technology today and the solutions now available. we will compare the technologies and the technological benefits, the installation precautions for safety and energy efficiency and finally the health risks and precautions....

a little bit of history

The creation of the modern electrical air conditioning unit is credited to the American inventor Willis H. Carrier. After graduating from Cornell University, The first air conditioner was designed and built in Buffalo, New Yok by Carrier and began working on 17 July 1902.   Many years later Carrier's technology was applied to increase productivity in the workplace, and The Carrier Air Conditioning Company of America was formed to meet the rising demand. Over time, air conditioning came to be used to improve comfort in homes and automobiles as well. Residential sales expanded dramatically in the 1950s.

In 1945, Robert Sherman of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.  Since then many improvements have been done to this original design still popular in USA but because it occupied the window space and created safety issues is not that popular in other countries. Newer designs of Split units (wall , duct, selling mount ) are now available in almost every country because of their variability.

Air conditioning (often referred to as AC, or as Air-con) is the process of removing heat and moisture from the interior of an occupied space to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans and other animals; however, air conditioning is also used to cool and dehumidify rooms filled with heat-producing electronic devices, such as computer servers, power amplifiers, and to display and store some delicate products, such as artwork.
Air conditioners often use a fan to distribute the conditioned air to an occupied space such as a building or a car to improve thermal comfort and indoor air quality. Electric refrigerant-based AC units range from small units that can cool a small bedroom, which can be carried by a single adult, to massive units installed on the roof of office towers that can cool an entire building. The cooling is typically achieved through the refrigeration cycle, but sometimes evaporation or free cooling is used.  Such a system also dehumidifies the air as it cools it. It collects water condensed from the cooled air doing so transfers heat from the air in the cooled area which must be vented to the outside air. Some AC systems reject or store heat in subterranean pipes.

  • Old ON/OFF Systems  - Personal Air-Condition for many years where Not energy efficient and their motors (Compressor, fans, etc)  and had two states of operation either working (ON) or not working(OFF) nothing in between! As technology was evolving and the first DC compressor was introduced we start seeing a hybrid system with only a DC compressor.
  • New all DC Inverter Systems  - In the newest Designs  manufactures equips their  Air-Conditions with all DC inverter Type motors (Compressor, fans, etc.) and with sophisticated electronics and functions considering many environmental parameters to successfully provide steady temperatures while saving a lot of energy.  Different manufactures distinguish themselves by providing more energy efficiency, better performance at extreme weather conditions, lower operating noise, faster reaching the desired temperature, different cleaning air technologies and self cleaning technologies.
  • The Marketing difference -  If you were lets say to compare two split air-conditions of 12000BTU each, one economical and a second one double its price certainly they can't be of same quality but why marketers market them as one of the same? Simply to confuse the buyer!! An Educated buyer will always read the manual of each air-condition and there should be able to find the difference. To try simplify this fake marketing similarity I would use the following example: by comparing two cars a cheap car and a Ferrari, both cars say that can reach the 100m barrier but they don't mention the how fast they will reach it.   Ferrari will do the 100m in 4 second and the cheap car will also do it, but in 20 sec. More details here! 
  • Energy efficiency- a key ingredient to energy efficiency is the proper installation, to do this right its important to consider two factors after first reading the manufactures manual: a) what is the refrigerant used in the unit and b) how may meters of coper piping is required in the installation by the manufacture in order to provide you the expected energy savings and measured results. Newer refrigerant R32, R290 now commonly used in all personal Air-conditions (is Flammable) and requires special consideration  for safety first and then energy efficiency! I in Residential installations for safety is suggested a minimum 3 meters of copper piping and this length may also be enough for the more expensive air-condition to meet their energy efficiency but for the more economical air-condition a 5-7m of copper piping may be required!  Every installation has is own requirements but in general Longer pipes always  within the manufactures' specs provide usually better energy efficiency results!
  • Having said that a lot of non Professional do installations with les than a meter of piping. Very Dangerous because you are not only loose the energy efficiency of your unit but you also get "a ticking Bomb that could go off any minute"!!" due to high pressure. That is why you have to read the installation manual especially in R32/R290 Installations and demand exactly what the manufacture suggest  for your  Air-condition in copper piping length. Sorter pipes you often see and get with a free installation package which is given with the purchase of your unit . wrong installations could result to this .... read more here!

most popular models

Portable units
A portable air conditioner can be easily transported inside a home or office. They are currently available with capacities of about 5,000–60,000 BTU/h (1,500–18,000 W) and with or without electric-resistance heaters. Portable air conditioners are either evaporative or refrigerative.  

Split systems
Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.

Mini-split (ductless) system
A mini-split system typically supplies air conditioned and heated air to a single or a few rooms of a building. Multi-zone systems are a common application of ductless systems and allow up to 8 rooms (zones) to be conditioned from a single outdoor unit. Multi-zone systems typically offer a variety of indoor unit styles including wall-mounted, ceiling-mounted, ceiling recessed, and horizontal ducted. Mini-split systems typically produce 9,000 to 36,000 Btu (9,500–38,000 kJ) per hour of cooling. Multi-zone systems provide extended cooling and heating capacity up to 60,000 Btu's. Large systems are known as VRF (Variable refrigerant flow) systems. Mini split ductless systems were invented by Daikin in 1973, and VRF systems were also invented by Daikin in 1982.

Advantages of the ductless system include smaller size and flexibility for zoning or heating and cooling individual rooms. The inside wall space required is significantly reduced. Also, the compressor and heat exchanger can be located farther away from the inside space, rather than merely on the other side of the same unit as in a PTAC or window air conditioner. Flexible exterior hoses lead from the outside unit to the interior one(s); these are often enclosed with metal to look like common drainpipes from the roof. In addition, ductless systems offer higher efficiency, reaching above 30 SEER.

The primary disadvantage of ductless air conditioners is their cost. Such systems cost about US$1,500 to US$2,000 per ton (12,000 BTU per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost more than twice as much as window units of similar capacity."

An additional possible disadvantage is that the cost of installing mini splits can be higher than some systems. However, lower operating costs and rebates or other financial incentives—offered in some areas—can help offset the initial expense.

Multi-split system
A multi-split system is a conventional split system, which is divided into two parts (evaporator and condenser) and allows cooling or heating of several rooms with one external unit. In the outdoor unit of this air conditioner there is a more powerful compressor, ports for connecting several traces and automation with locking valves for regulating the volume of refrigerant supplied to the indoor units located in the room.

A large Multi Split System is called a Variable refrigerant flow system and can be used instead of a central air conditioner system, as it allows for higher energy efficiency but it is more expensive to purchase and install.

Difference between split system and multi-split system:
The difference between separate split system and multi-split system with several indoor units is that all the indoor units are connected to the main external unit, but the principle of their operation is similar to a simple split-system.
This unique feature of a multi-split might be the right solution for maintaining the microclimate in several offices, shops, large living spaces. The main external unit can be connected to several different indoor types: floor, ceiling, cassette, etc. with just only a few of this outdoor units you do not worsen the aesthetic appearance of the building.

Multi-split system installation considerations
Before selecting the installation location of air conditioner, several main factors need to be considered. First of all, the direction of air flow from the indoor units should not fall on the place of rest or work area. Secondly, there should not be any obstacles on the way of the airflow that might prevent it from covering the space of the premises as much as possible. The outdoor unit must also be located in an open space, otherwise the heat from the house will not be effectively discharged outside and the productivity of the entire system will drop sharply. It is highly advisable to install the air conditioner units in easily accessible places, for further maintenance during operation.
The main problem when installing a multi-split system is the laying of long refrigerant lines for connecting the external unit to the internal ones. While installing a separate split system, workers try to locate both units opposite to each other, where the length of the line is minimal. Installing a multi-split system creates more difficulties, since some of indoor units can be located far from the outside. The first models of multi-split systems had one common control system that did not allow you to set the air conditioning individually for each room. However, now the market has a wide selection of multi-split systems, in which the functional characteristics of indoor units operate separately from each other.
The selection of indoor units has one restriction: their total power should not exceed the capacity of the outdoor unit. In practice, however, it is very common to see a multi-split system with a total capacity of indoor units greater than the outdoor capacity by at least 20%. However, it is wrong to expect better performance when all indoor units are turned on at the same time, since the total capacity of the whole system is limited by the capacity of the outdoor unit. Simply put, the outdoor unit will distribute all its power to all operating indoor units in such a way that some of the rooms may not have a very comfortable temperature level. However, the calculation of the total power is not simple, since it takes into account not only the nominal power of the units, but also the cooling capacity, heating, dehumidification, humidification, venting, etc.
Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.

Energy transfer
In a thermodynamically closed system, any power dissipated into the system that is being maintained at a set temperature (which is a standard mode of operation for modern air conditioners) requires that the rate of energy removal by the air conditioner increase. This increase has the effect that, for each unit of energy input into the system (say to power a light bulb in the closed system), the air conditioner removes that energy. To do so, the air conditioner must increase its power consumption by the inverse of its "efficiency" (coefficient of performance) times the amount of power dissipated into the system. As an example, assume that inside the closed system a 100 W heating element is activated, and the air conditioner has a coefficient of performance of 200%. The air conditioner's power consumption will increase by 50 W to compensate for this, thus making the 100 W heating element cost a total of 150 W of power.

It is typical for air conditioners to operate at "efficiencies" of significantly greater than 100%. However, it may be noted that the input electrical energy is of higher thermodynamic quality (lower entropy) than the output thermal energy (heat energy).

Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration", with each approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts. Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.

Seasonal energy efficiency ratio
For residential homes, some countries set minimum requirements for energy efficiency. In the United States, the efficiency of air conditioners is often (but not always) rated by the seasonal energy efficiency ratio (SEER). The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt hours (W·h) during the same period.
SEER = BTU ÷ (W·h)
this can also be rewritten as:

SEER = (BTU / h) ÷ W, where "W" is the average electrical power in Watts, and (BTU/h) is the rated cooling power.
For example, a 5000 BTU/h air-conditioning unit, with a SEER of 10, would consume 5000/10 = 500 Watts of power on average.

The electrical energy consumed per year can be calculated as the average power multiplied by the annual operating time:

500 W × 1000 h = 500,000 W·h = 500 kWh
Assuming 1000 hours of operation during a typical cooling season (i.e., 8 hours per day for 125 days per year).

Another method that yields the same result, is to calculate the total annual cooling output:

5000 BTU/h × 1000 h = 5,000,000 BTU
Then, for a SEER of 10, the annual electrical energy usage would be:

5,000,000 BTU ÷ 10 = 500,000 W·h = 500 kWh
SEER is related to the coefficient of performance (COP) commonly used in thermodynamics and also to the Energy Efficiency Ratio (EER). The EER is the efficiency rating for the equipment at a particular pair of external and internal temperatures, while SEER is calculated over a whole range of external temperatures (i.e., the temperature distribution for the geographical location of the SEER test). SEER is unusual in that it is composed of an Imperial unit divided by an SI unit. The COP is a ratio with the same metric units of energy (joules) in both the numerator and denominator. They cancel out, leaving a dimensionless quantity. Formulas for the approximate conversion between SEER and EER or COP are available.

(1) SEER = EER ÷ 0.9
(2) SEER = COP × 3.792
(3) EER = COP × 3.413
From equation (2) above, a SEER of 13 is equivalent to a COP of 3.43, which means that 3.43 units of heat energy are pumped per unit of work energy.

The United States now requires that residential systems manufactured in 2006 have a minimum SEER rating of 13 (although window-box systems are exempt from this law, so their SEER is still around 10).

Health effects
In hot weather, air conditioning can prevent heat stroke, dehydration from excessive sweating and other problems related to hyperthermia. Heat waves are the most lethal type of weather phenomenon in developed countries. Air conditioning (including filtration, humidification, cooling and air disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. It is sometimes recommended for home use by people with allergies.
Poorly maintained water cooling towers can promote the growth and spread of microorganisms such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced. The state of New York has codified requirements for registration, maintenance, and testing of cooling towers to protect against Legionella.

<<<< Περισσότερα σχετικά άρθρα >>>>