Air conditioners: what are they, how do they work
Air conditioner
The air conditioner is a machine capable of developing heat sensitive (positive or negative) that is exchanged with a fluid, which in turn put into circulation gives this heat to an environment for the purpose of innalzarne or lower the temperature.
1. Historical Background
Around 1911 Willis Carrier (United States) took advantage of the changes of state of a gas in order to obtain a change is positive ("hot") and negative ("cold") environment. [] Carrier worked as an engineer in a company that supplied industrial plants. After a year of work he was given the task of solving the problem of controlling humidity in a printing shop in Brooklyn, where the paper was just unusable due to excessive moisture in the air.
In the past to solve this problem was the increased air velocity, or some window opened to counteract the humidity with an opposite current. The humidity was also a serious problem in terms of productivity, because it led to an interruption of the workers and then the job. Carrier completed the first draft of an air conditioning system on July 17, 1902, and the technology that was the basis of his system is similar to that of the plants that we find on the market today.
The term "air conditioning" dates back to Stuart W. Cramer, who became interested in the study as Carrier humidity and air conditioning.
2. Operation and construction details
The operation of an air conditioner is based on the use of a thermodynamic cycle.
The air conditioner is typically consists of the following essential elements:
- The compressor
- the capacitor
- the evaporating
- the expansion device.
To complete the air conditioner, in addition to these parts, there is a gas, which has the function of heat transfer fluid.
The gases used in air conditioners are (or were):
- R12: industrial air conditioners (now outlawed);
- R22: civil conditioners and tertiary (now outlawed);
- R407c: civil conditioners and tertiary;
- R410a: civil conditioners and tertiary sectors.
There are also a series of components and accessories that serve to complete the operation of the system, such as valves, pressure switches, fans, remote control, sensors, electronic boards.
In civilian use is common configuration which has two separate units:
- an external drive, the host conditioner motor characterized by the radial fan
- an internal one (split), which provides in circulating air (conditioned or not), spreading the premises through a specific opening.
2. 1. Appearance
The air conditioners may be comprised of two units, one said internal unit and the second said external unit. Between the two units run two copper pipes and connections of control and command, while the power supply is usually only brought to the outdoor unit.
Both the two units require a drain to evacuate the water that is formed by condensation. Lately revenue in commercial machines are formed by a single element which, if leaning against a wall, perform both functions of those described before, but with significant performance limitations.
The indoor units can then be divided into five types of construction:
- wall: for wall installations in high position;
- Floor: type fan coil;
- Console: for ceiling installation without false ceiling;
- Cassette: for recessed installation in suspended ceilings;
- ducted: assembled for installation in air ducts and anemostats.
3. Types
3. 1. Cooling only and heat pump
The air conditioners are divided into two large families:
- only those called cold
- those known to the heat pump.
The substantial difference is that those in the heat pump, in addition to cool the air in summer, in winter can also heat by reversing the operation cycle.
3. 2. On-off switch and inverter
A further distinction is that related to their power and their operations. Under this point of view, there are two big families:
- air conditioners on-off
- air conditioners with inverter.
The technology of air conditioners is very simple on-off (costs less) and has a high consumption, because when you turn goes straight to maximum power no matter how much they actually serve. The conditioners inverter instead have a technology called "modulating" or during their operation, decreases the power required in function of the cooling obtained gradually up to the minimum necessary to maintain the set temperature, with a considerable energy saving.
If the air conditioner is operated for many hours (at night for example) is economically convenient model inverter, otherwise the higher cost compared to the on-off pattern is not amortized, because the modulating function occurs after at least 2-3 hours from first time. []
4. Appearance energy
The air conditioners are bound by European rules on energy saving and must be classified by the manufacturer according to the class of energy consumption. The classes of energy consumption are:
A: very good
B: good
C: average
Q: mediocre
E: Low
F: very low
G: bad.
The highest classes (AB) are usually with inverter technology, a conditioner on-off can be included in the class A (or below) in the case showing consume what the type of appliance (in this case the air conditioner) of the same class, with inverter technology or not. Often conditioners with on-off technology do not go beyond the class C.
The European Community directive is no. 94/2/EC of 21 January 1994 and 12 April 1998 the Decree of the Ministry of Industry and Commerce.
The power of an air conditioner is measured in BTU / I frigorie / h.
5. Regulatory requirements and environmental
There are no national laws prohibiting the wall installation on the facades of buildings as some articles of the Civil Code of the condos in lends itself to interpretations. In fact, the law 10/91 and Presidential Decree 412 do indicate and recommend the use of machines in the heat pump. The problem stems from the aesthetic, many municipalities enact regulations for certain paths of virtue, to avoid the sight of the outdoor units that are invasive and unpleasant.
Even condos condominium may adopt regulations, approved at the meeting, which prohibit the installation of outdoor units for aesthetic reasons. The argument is often controversial as a collective good (the beauty of the building) collides with a private benefit (the ventilation of the housing unit). The bond is often exceeded, if the person has need of conditioning for health reasons, with a medical certificate will prevent the house rules but not without problems. In the worst case, are mounted air conditioners with no outdoor unit.
5. 1. Reference standard
Despite the prevailing ignorance in these machines fall under the Law 10/91 and the consequences of the technical report in accordance with that law.
Also fall under the Law 46/90 as they use gas and electrical connections of various types.
It should be specified (for the air conditioners intended for the civil environment) which falls only on the connection to the electrical power to the power of the air conditioner with the electrical system of the house. The connection between the two machines (hydraulic or electric) does not fall in the law because European legislation considers the set of two machines (internal + external) only one component then as if it were a single appliance.
The technical standards of reference are:
UNI EN 378-1: "Refrigerating systems and heat pumps" - ENVIRONMENTAL AND SAFETY REQUIREMENTS - Basic requirements, definitions, classification and selection criteria.
UNI EN 378-2: "Refrigerating systems and heat pumps" - SAFETY REQUIREMENTS AND ENVIRONMENTAL - Design, construction, testing and marking documentation.
UNI EN 378-3: "Refrigerating systems and heat pumps" - SAFETY REQUIREMENTS AND ENVIRONMENTAL - Installation site and personal protection.
UNI EN 378-4: "Refrigerating systems and heat pumps" - SAFETY REQUIREMENTS AND ENVIRONMENTAL - Operation, maintenance, repair and use.
IEC standard 64-8/7 (Electrical systems using a nominal voltage not exceeding 1000 V ac and 1500 V dc - environments and special applications)
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Source:
Italian version of ReteArchitetti.it