Checking the pressure in the split system

Characteristics of the coolant (freon) R22, limitation of its use

In order to understand what pressure in split-system is necessary you should consider the basic technology of the whole device.

It is based on application of the law of physics about the properties of liquid. So, as it evaporates, it is able to absorb heat. When the liquid is converted into a gaseous state, the heat is released into the atmosphere.

  • An external compressor is used to regulate the movement of the main freon refrigerant.
  • In order for the refrigerant to change from liquid to gaseous, an evaporator is used.
  • For freon to change back to a liquid state, it is necessary to have a condenser.
  • For correct change of Freon state it is necessary to have low pressure in split system. It is provided by the thermostatic valve.
  • To increase efficiency and to speed up the work of the device the fans are installed.

So, there must always be high pressure on the outside of the device. And in the interior, it’s low.

Types of Freon for air conditioning systems

For about half a century, the primary refrigerant in residential air conditioning systems has been Freon 22. Since about the mid-80s of the last century, its use has been severely persecuted because chlorine, which is a component of this gas, allegedly affects the ozone layer that protects our planet from the harsh ultraviolet. This throw in though has not been 100% proven, but this information has led to the development of new and safer refrigerants: freons R410 and R407.

New types could not fully oust R22 from the market of climatic equipment due to simplicity of servicing and some physical properties of this gas. Today, in domestic split systems, the most commonly used ones are: R22; R410 and R407.

Freon R22 is most commonly encountered in air-conditioning systems used in domestic appliances, production, and transportation of perishable goods. Since practically all the refrigeration equipment manufactured by the end of the last century has been operating on this type of refrigerant, charging of air-conditioners with this gas is the most demanded.

Freon R410 is a colorless gas, which is a full-fledged replacement for its predecessor. Nowadays, it is used in new air-conditioning equipment, regardless of its purpose. One of peculiarity of this gas is the fact that in case of its leak from air conditioner, more than 35%, it is necessary to refill fully the equipment.

Freon R407 is nothing but a mixture of several gases, each of which is responsible for certain physical properties of the refrigerant. Most often used in multizone or semi-industrial split systems. It is impossible to top up the climatic equipment with this type of gas: in case of leakage it is necessary to merge it completely and only after this top up procedure should be carried out.

Ways of charging air conditioner with freon

There are several basic methods of charging of refrigeration systems with freon applied to house air conditioners (splits), multi-splits, mobile and multizone systems.

Filling the air conditioner with your own hands will require the following set:

  • pressure gauge;
  • vacuum pump;
  • bottle with freon;
  • building scales;
  • Locksmith tools. a Swedish wrench, hexes, screwdriver.

It is possible to buy a manometer and vacuum pump instead of a manometer and a vacuum pump.

Filling by weight

If it is necessary to charge completely empty air conditioner with 22 or 410 gas, the process is as follows.

Vacuuming. Screw pressure gauge on the shredder and open the tap on it. Turn on the vacuum pump and wait 10 minutes. Close the tap on the manometer and switch off the pump.

checking, pressure, split, system

Connecting of bottle with freon. A container with gas is turned upside down and put on the scales, which indexes are preliminary reset to zero values. Open the stopcock on the manometer and pour the necessary quantity of the refrigerant according to the scales.

The rate for each air conditioner and type of gas filled in the compressor are given in the technical documentation and on the nameplate.

Close the valve and disconnect the pressure gauge, then screw the caps on the ports. Turn on air conditioner and check its functionality.

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This method is considered the most correct, but it is complicated by the need to have expensive scales for weighing freon.

If it is required to fill up a conditioner with freon by oneself, firstly one completely squeezes out its rests in manometric station for the collection and then one pours the gas by weights. This is due to the fact that this type of Freon consists of a mixture of different gases with different degrees of volatility. If one of the components leaks in a larger volume, the composition changes and consequently the necessary properties of the refrigerant are lost.

If it is necessary to fill conditioner with freon R22, then one should use such method as charging conditioner according to pressure.

Filling according to pressure

At first one should connect the manometer to the gas port of air-conditioner which works for cooling. Working pressure of the unit must be 3-3,5 atm. If it is below these pressure points, you must refuel. For this purpose, the cylinder with freon is plugged in and starts charging it in small portions into the system by opening the taps on manometer for 5-10 seconds.

To avoid burning your hands with gas, it is more convenient to use quick disconnect couplings.

This way is convenient exactly when it is necessary to top up the air conditioner with your own hands with a small portion of the refrigerant R22. In all other cases the simplest and optimum method is refueling with scales, that is by mass.

Superheat and subcooling

A reasonably accurate method is to charge the air conditioner by overheating or undercooling. The whole point is to focus on the temperature difference.

checking, pressure, split, system

In the case of subcooling we mean the ratio of temperature values of liquid and condensation at the same pressure. It is possible to define the condensation temperature as follows: using manometer, its pressure is measured and then the data is correlated with the scale values of the manometer manifold depending on the refrigerant. To determine overheating they compare the temperature values of gas in normal state and when it is boiling under the same pressure.

Overheating and undercooling indicate a refrigerant leak and the need for topping up.

These methods are not suitable for charging of home air conditioners, i.e. wall-split-systems. But they are very convenient for semi-industrial installations, because their external unit has the required fittings. In addition to tools infrared thermometer is needed.

A non-professional will hardly be able to charge conditioner with the help of these two methods, as they require sufficient knowledge in the sphere of air-conditioning systems. Though, simplicity and availability of the previous methods for an average person is also a questionable question.

Charging the air conditioner according to current

Many masters do not use this method, but its application is fully justified in the cases when there is no possibility to use scales for freon weighing. How to charge conditioner by oneself according to the current?

To determine the operating current of the compressor, special clamp meters are needed, which are applied to the phase of the power supply wire of the operating outdoor unit. If the received values are lower than those indicated in the manual or on the nameplate, and the pipe is frosted, the freon is topped up to equalize the indicators.

How to Leak Test an AC With Nitrogen Pressure

All the rest steps are identical to the stages of charging the air conditioner with freon according to the weights that can be seen on the video at the end of the article.

This method is also applicable in the case of fixing the consequences of the leak in the semi-industrial equipment.

If length of freon line of a conditioner exceeds the length of a line without refueling indicated by the manufacturer, but does not exceed the maximum allowed value, it is necessary to refuel the device on the calculation 30g of gas per meter (up to 3,5 kW).

Methods of controlling the amount of freon

Figuring out how to charge the split system with freon yourself, you should remember that the amount of refrigerant must be sufficient, but not excessive. If there is too much gas in the circuit, the operation of the device will be seriously disrupted because the refrigerant simply will not have time to evaporate. This can seriously damage the compressor.

checking, pressure, split, system

This situation is worse for the device than if the system will be missing a few grams of refrigerant. That is why during charging it is necessary to organize control of freon amount, supplied to the system.

  • by measuring the change in mass of the refrigerant bottle;
  • Considering the pressure in the system, which must reach a certain value;
  • checking the condition of the circuit through the sight glass;
  • Considering the temperature change at the fan of the indoor unit.
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The easiest way to control the quantity of freon is to record the change in the weight of the cylinder. For this purpose before charging they put a container with the refrigerant on the scales, zero the result and watch for changing of indicators with the opened ballon valve.

As soon as its weight decreases by the necessary value the filling is stopped at once. Of course, this method is used only for complete charging of the circuit. If you just need to refill the system, you first need to know the weight of the refrigerant that is already inside, and this is difficult to do at home.

There are professional scales, designed for these purposes, but many masters make do with inexpensive domestic models.

The instrument must comply with the following requirements:

Electronic scales are the most convenient to use as they make it easier to track the change in weight of the refrigerant bottle.

Another available option is to bring the pressure inside the circuit up to the desired value. To perform such filling you need a pressure gauge manifold. This device is used for pressure evaluation inside the system.

The refrigerant is fed to the circuit in small portions, constantly checking the pressure with the standard value until a match is reached.

Before charging the system with refrigerant, find out why there is a leak, and then correct the problem. Rechecking is done after the job is done

The manifold is rather expensive equipment, which doesn’t make sense to buy only to use once in several years. It is useful not only at the stage of pumping freon, but also when dehumidifying and evacuating the system. You can borrow such a device from a familiar craftsman or rent from a specialized outlet.

The method using a sight glass is available to professionals. It consists of watching the state of the refrigerant flow, monitoring the moment when the air bubbles have disappeared. In home conditions the first two methods are often used.

Temperature measurement is a simple but not very reliable method. The fan when the circuit is full, the temperature should usually be about eight degrees, although there are models for which this figure is five, a deviation of a couple of degrees is allowed. The refrigerant is introduced in small portions, periodically making measurements.

What the pressure should be and how to recharge the air conditioner after checking

The pressure in the different system circuits depends on a number of factors. As noted earlier, the air temperature and the type of working fluid affects this indicator to a large extent.

Anyhow, as a rule, as a rule, modern systems of air conditioning are charged with universal kinds of refrigerants which have similar working parameters. The most common of these is the so-called 134 Freon.

Thus, in warm weather, this type of refrigerant should be in the air conditioning system at a pressure equal to:

It must be remembered that this is one of the key performance characteristics of the car’s climate systems. It makes possible to judge about serviceability of its working assemblies and elements.

A procedure to measure the pressure of the air conditioner often results in a loss of refrigerant. This makes it necessary to refill the system to the required value.

To perform topping up the system one should have with him some equipment. The list of equipment includes:

  • pressure gauge block;
  • A pair of hoses for the air conditioner;
  • The reservoir with the working fluid;
  • Stop valve fittings and transition fittings.

To cope with topping up the system with freon will be able to even a novice motorist, you just need to follow the step-by-step instructions:

  • Screw the fitting with a stopcock to the freon tank;
  • connect the fitting to the hose;
  • connect the other end of the hose to the gauge station;
  • Connect the remaining hose with a fitting to the other outlet of the pressure gauge unit;
  • proceed directly to filling up the system by opening the tap.

To define charging capacity of concrete car air conditioning system, it is enough to have a look on information board under a hood of your car. Once you have studied it, you will know the type/brand of working fluid and the volume of the system.

Why the pressure in split-system does not depend on quantity of freon

Freons, used in air conditioning systems and refrigerators, circulate inside a closed circuit, consisting of two heat exchangers (evaporator and condenser), compressor and throttle valve. In the first radiator, the refrigerant changes from liquid to gas phase, drawing heat from the room air, while in the second, it changes back to liquid.

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Recall: Freon is a substance that boils at negative temperature (under normal conditions). To raise the evaporating / condensing point, the pressure in the circuit is forcibly increased by the compressor.

The nomogram reflects how much R410a refrigerant pressure changes depending on the ambient temperature. There are no clearly defined limits on the head of the refrigerant in the system, depending on several basic factors:

  • Ambient temperature and air temperature in the room;
  • operating mode of the air conditioner;
  • the degree of contamination of the heat exchangers and air filters;
  • the brand of refrigerant charged;
  • other less significant factors.

Reference. Household chillers are usually charged with two brands of freons. R22 and R410a. Car air conditioners are filled with R134a, older models. with R12.

The actual working fluid pressure changes several times during the day due to weather and switching cooling modes. The quantity of refrigerant has no influence, except that the substance will escape from the system completely. In confirmation of these words let’s describe the experiment published in the technical manual of the famous author Patrick Kotzaoglanian:

  • Let’s take 2 closed tanks imitating the freon circuit of the air conditioning system. Let’s connect the pressure gauges and fill them with different amounts of refrigerant R22.
  • Let’s heat the vessels to the same temperature of 20 °C. All three gauges show 8 bar regardless of the liquid level in the tank. Why?
  • Freon evaporates on heating, but gas needs 30 times the volume of liquid. Vapor phase quickly fills free space and gets saturated, pressure in the vessels grows. When the heating stops, the readings are the same.
  • To check the statement let’s heat 2 reservoirs to the temperatures of 27 and 34 degrees. Pressure gauges will show up to 10 and 12.2 Bar respectively.

Conclusion. Working pressure in an air conditioner does not depend in any way on freon volume inside the system; to measure it without taking into consideration the temperature is senseless.

Amount of refrigerant to be topped up

How much refrigerant should be charged into the system and how much freon is there. these data are usually specified by the manufacturer. It is indicated on the metal plate, and the plate itself or in other words on the nameplate is always located on the inside casing of split system. Refilling of the air conditioner is carried out taking into account the data indicated there.

The amount of gaseous substance, which it is necessary to top up the air conditioner, usually is calculated with the help of such device as a pressure gauge. Using it, they define the value of pressure value in a cooling contour.

General Information

One of the most important components of any air conditioner is freon, also known as refrigerant or simply the refrigerant. There are dozens of freon varieties on the market, but only two of them are often used in household air conditioners: R410A and R22.

If there is insufficient quantity of freon in air conditioning system, the conditioner can fail. The same happens when the amount of refrigerant in the air conditioning system is exceeded.

In order to determine the amount of refrigerant and in general to adjust the work of the unit you need to measure the freon pressure in air conditioners. Further we will tell you how to do it. Keep in mind that a 100% accurate measurement is almost impossible, because many factors affect this indicator. But you can find out approximate indices.

Prevention of pressure rise and fall in the split system

In order that the pressure level in an air conditioner is always kept within the limits of necessary norms, the following preventive measures should be constantly carried out:

  • It is necessary to clean all blocks of appliance at least once a week.
  • Periodic cleaning and filter replacement.
  • Emptying the drainage system.
  • Timely filling of the device with freon. At least once a year.
  • Internal parts cleaning from dirt and dust at least once in half a year.
  • Disconnection of the entire system in the cold season when the temperature is below 5 degrees.
  • Do not try to disassemble and repair this device by yourself if you discover any faults. This may result in a more serious failure. It is recommended to apply to professionals.

Mini-Split Heat Pump: Nitrogen Pressure Test

Constant control of pressure in split-system will let you prolong term of its exploitation and guarantee its correct work.

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