Components of the air-conditioning system, their organization and check

In this chapter you can find necessary information on the components of the air-conditioning system. Here one will see detailed description of their organization, operation and necessary checkouts. Special attention should be paid to compressor. In this chapter there are described only organization and elementary checkouts which can be performed by everybody, but more complicated repair comprehensible only for specialists is described in the second part of the book.

• Oil coolants
• Compressor
• Condenser
• Receiver-dehydrator
• Expansion valve
• Evaporator
• Accumulator
• Expansion tube

Attention: Before performing any operations connected with the air-conditioning system, one should familiarize with the safety measures described in the first chapter of the second part of this book.

Recently due to rapid advancement of compressors, development of facilitated small compressors and application of new kinds of refrigerants, requirements to the function of oil coolants increase even more. The function of the oil coolant is important as a link for ensuring the air-conditioning system safety and resistance to higher or lower temperature.

Analyzing the function of cooling liquid in the system, then

• Outlet valve: in the compressor, outlet valve zone is the most high-temperature place. Here carbon is generated, and it is necessary to prevent its lamination.
• Condenser: biggest amount of oil entering the refrigerant system, together with liquid refrigerant, should keep liquid state in order not to prevent heat exchange or flow from hardening on condenser walls. Oil should not contain solid substances preventing expansion, as well as generate such substances.
• Evaporator: During the refrigerating cycle, oil in the evaporator which is the most low-temperature zone, should not make crystal fallout. Moreover, oil should not contain moisture and harden. In case of occurring such phenomena, they prevent flow of the refrigerant and reduce refrigeration efficiency.

Peculiarities of oil coolant

Specificity:

Oil coolants should have specific characteristics which common lubricants do not possess. Though common lubricant mainly should meet only requirements as to lubricating characteristics, refrigerating oil should not harden when mixing with the refrigerant and at low temperature, not oxidize at high temperature, not react with the refrigerant, not cause an accident reacting with materials used in the equipment.

Chemical stability:

As one of ways of estimation of stability of cooling oil, they carry out testing in the hermetically sealed tube. This test is carried out in a heat resisting glass test tube by placing in it refrigerant actually used in the compressor (R-I2), metal (Fe, Си, А1) and oil. While testing on the hermetically sealed tube in a heat resisting glass test tube they use oil 0,5 ml, refrigerant R-12 0,5 ml. After having placed copper and iron as the catalyst, they heat up from temperature 175°С within 14 days, measure amount of R-22 decomposed out of R-12.

In this test the less is the amount of decomposition, the better is stability of cooling oil.

Also it is necessary to observe and check the condition of sticking at surfaces of iron sheets, corrosion of copper wires, color of a blend.

Here it is necessary to notice that testing should be considered as a way of elimination of bad oil instead of a way of selecting one proper. For correct decision making about conformity of a cooling oil, the results of test received on the real compressor are important.

Low temperature property:

Cooling oil adjoins to a refrigerant at low temperature. Not only that the joint coexistence with a refrigerant is desirable at low temperature and it is necessary that wax did not decompose on wax-like deposits.

Cooling oil even at low temperature does not harden, i.e. has low temperature of fluidity and simultaneously hardly decomposes deposits, and the less is decomposition, the more preferable it is.

Greasing property:

At excessive refinement of cooling oil, aromatic components sharply decrease. Though among aromatic components there are substances with bad chemical stability, but if aromatic components are pure, there is an active influence of these components on the stability to oxidation and limiting pressure. Therefore, there is a necessity of application of a manual way of refinement for preservation of the specified effective elements. Thus, it is necessary to choose oil with good greasing property that even at application in the real machine there was no fusion.

Typical data of SUNISO cooling oil

Requirements to cooling oil

It should have superficial durability and good insulating property.

It should not contain impurities such as moisture and various acids.

It should have good separability with water and appropriate viscosity.

It should have good separability with a refrigerant and it should not enter into chemical reactions.

It should contain small amount of crystallization elements and have stability concerning acids.

Special phenomena and their displays

Foaming.

In freon refrigerating installations when starting the compressor, pressure in a crankcase sharply falls and a refrigerant dissolved in oil, sharply begins to evaporate, the surface of oil begins to rage and there is a foam. If this phenomenon will proceed long time, then due to infringement of greasing of rubbing parts there may jam and burn down the compressor.

When penetration from the sucking side of the compressor of a big amount of oil to the cylinder, because of compression of incompressible oil there is a danger of damage of the valve saddle plate. Besides there is an insufficiency of oil in a crankcase as a plenty of oil will proceed in various parts of the device. Insufficiency of oil becomes the reason of jamming of the compressor.

The phenomenon of a copper covering.

There is a phenomenon when in the refrigerating devices using a freon system refrigerant, copper after having dissolved in oil, together with a refrigerant, circulates in the device, then again settles on a metal surface and covers it, thus:

• the active part of a backlash decreases, the compressor gets jammed and becomes disabled;
• in the device either moisture is too much, or the higher is the temperature, the easier the moisture appears in the cylinder and on the valve plate;
• the more molecules of hydrogen R-22 contains in comparison with R-12 and R-30 in comparison with R-22, and the more MAX elements are, the stronger is this phenomenon.

Attention: In the air-conditioners filled with R-134a refrigerant it is used polyalkylene- glycol oil (PAG), this oil is incompatible with mineral oil used in the air-conditioners with R-12 refrigerant.