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Make the air conditioner gas charge in liquid form. Why?
If you ask yourself this question, we will explain the reasons for charging or recharging gas in this way, as many people are unaware that many of the refrigerant gases used in our air conditioning or air conditioning equipment are actually composed of a mixture of gases and not pure gases. We will also explain the differences between azeotropic and non-azeotropic mixtures and how both behave in the event of a gas leak.
Pure gases and mixtures
Pure gases
Pure gases are substances that are formed by a single type of component or molecule. Among these types of refrigerant gases we can find R22, R134a and R12. As these gases have a basic composition of one component, they do not have the problem of non-azeotropic mixtures when there is a leak in the refrigeration circuit.
Mixed gases
Mixed gases can be grouped into three large families: azeotropic mixtures, quasi-azeotropic mixtures and non-azeotropic mixtures. All of them have the common characteristic that they are formed by the mixture of two or more pure gases but each one has its special characteristics.
Non-azeotropic gases or non-azeotropic mixtures
These gases are formed by two or more pure gases with a different sliding and boiling temperature between them. This means that in the event of a leakage, the gases forming the mixture will tend to be lost in different quantities, which will break down the mixture and influence the performance of the machine. A clear example of this type of non-azeotropic mixture that is currently used is refrigerant R407.
In the example of R407 gas we can see that it is made up of three components: tetrafluoroethane (R-134a) at 52%, pentafluoroethane (R-125) at 25% and difluoromethane (R-32) with 23% of the total mixture.
Non-azeotropic gases must always be charged in a liquid state.
Azeotropic gases or azeotropic mixtures
Like non-azeotropic mixtures, azeotropic mixtures consist of two or more pure gases. The difference is that these mixtures do have the same boiling point, so that in the event of a loss of gas, it will maintain its composition and performance. An example of an azeotropic gas is R-502, which can be charged in a gaseous state even if it is a mixture of several pure gases.
Quasi-azeotropic gases or quasi-azeotropic mixtures
These mixtures, even if they are non-azeotropic, have a very similar boiling temperature and therefore tend to ‘lose’ the same amount in the event of a gas leak. A very common example of this type of gas at present is R-410, which could be recharged both in a liquid and gaseous state. However, since it is not a 100% azeotropic gas, it is always advisable to charge or recharge it in a liquid state.
Non-azeotropic and quasi-azeotropic gas loading
In a bottle of refrigerant as in any air conditioning equipment we find the refrigerant in both liquid and gaseous state. In the bottles where these refrigerants are stored the liquid state will be in the lower part of the bottle and in the upper part we will have the same refrigerant in a gaseous state.
The first thing we have to understand is that in the liquid state the mixture of the refrigerant is perfect since it was manufactured, something that does not happen in the gaseous state, since this mixture of refrigerants corrupts when evaporating at different temperatures, so a charge in the gaseous state will cause the mixture we are putting into our equipment is not a perfect mixture, so the operation of our unit will not be adequate and may cause more serious problems in the long term.
This also happens when there is a loss of gas, the amount of gas that is lost due to a leak in this type of gas is not exact and therefore the mixture decomposes. In this situation, it is always advisable to empty the circuit with the remaining gas in this type of non-azeotropic gas and carry out a complete gas charge by weight and in liquid state.
Azeotropic gas loading
Given the composition of azeotropic gases and the same boiling temperature, they have no problem being charged in both a liquid and gaseous state. Nor will there be any problems in recharging an installation where a leak has occurred as the mixture will maintain its composition and therefore will not influence the drop in performance.