Modern refrigeration units are complex systems where the compressor plays the role of a heart that circulates the refrigerant. Pressure violation in the circuit often becomes the root cause of the lack of cold, the appearance of condensation or uncharacteristic noise during operation of the unit. Diagnostics of this parameter requires not only special tools, but also a clear understanding of the physical processes occurring inside a closed cycle.
Owners of household appliances often wonder how to check the pressure of a refrigerator compressor without resorting to an expensive call to a technician. Independent diagnostics is possible, but it requires strict adherence to security measures and the availability of a basic set of tools. Errors at this stage can lead to depressurization of the system or failure of expensive components.
The key point is to understand that the pressure in the system is non-uniform and depends on the temperature of condensation and evaporation of freon. Gauge station allows you to read accurate readings and compare them with passport data compressor. In this article we will analyze in detail the algorithm of actions, standards for various types of refrigerants and methods for interpreting the data obtained.
The principle of operation of the compressor and the role of pressure in the circuit
The main task of the compressor is to compress the gaseous refrigerant and move it through a closed circuit circuit. Discharge pressure is created in a condenser, where the gas turns into a liquid state, giving off heat to the environment. It is this pressure difference that ensures a continuous cooling cycle inside the chambers of your refrigerator.
On the suction side, on the contrary, low pressure is maintained, which allows freon to boil at low temperatures, effectively removing heat from the products. If compressor is not able to create the necessary difference, the efficiency of the entire system drops to zero. Mechanical wear of the piston group or valves often causes a decrease in compression.
It is important to note that at different points in the circuit the indicators will differ dramatically. For example, at the outlet of a compressor the pressure can reach tens of atmospheres, while at the inlet it is close to vacuum or minimum values. Hydraulic resistance The capillary tube plays a key role here, separating the high and low pressure zones.
⚠️ Attention: Working with refrigerants requires caution. Contact of freon on the skin can cause frostbite, and inhalation of vapors can cause toxic poisoning. Always work in a well-ventilated area.
Understanding these processes is necessary for proper installation of measuring instruments. Incorrect connection of the pressure gauge can distort the readings or cause injury. Kinetic energy The compressed gas is large, so all connections must be tight and reliable.
Necessary tools and preparation for diagnosis
To carry out high-quality diagnostics, you you will need specialized equipment, which is not always available in the home craftsman’s arsenal. The main tool is pressure gauge station (collector), which allows you to control system parameters. Without this device, the check will be only indirect.
You will also need a set of hoses with quick-release connections corresponding to the type of refrigerant. For R134a and R600a different types of fittings are used, which eliminates confusion and filling with unsuitable gas. Ignoring this rule may result in damage to the compressor or a fire hazard.
The list of required equipment also includes:
- 🔧 A set of wrenches and pliers for accessing the service fitting.
- ⚡ Multimeter for checking the electrical circuit compressor.
- 🧤 Protective gloves and glasses to prevent injuries.
- 📋 Passport data of the refrigerator indicating the type and rate of freon filling.
Before starting work, you must disconnect the refrigerator from the power supply. Safety above all, since work is carried out with electricity and pressurized gas. Only after complete de-energization can you begin to dismantle the protective panels.
In some models, access to the compressor is limited by plastic casings or metal screens. Carefully remove them to ensure easy access to service fitting. If there is no standard fitting, you will have to cut it in, which requires soldering and skills in working with copper pipes.
Step-by-step instructions: how to connect pressure gauge
The process of connecting measuring equipment requires consistency and accuracy. First, determine the type of refrigerant indicated on the technical label, usually located on the back wall or inside the chamber. This will determine what hose and adapter you will need to connect to the service port.
If the system has a Schrader valve (similar to a car nipple), the process is simplified. Screw the blue low pressure hose of the gauge station onto the valve. Make sure that the valve on the manifold is closed to avoid a sudden release of gas. Tightness of the connection is a critical parameter that affects the accuracy of measurements.
☑️ Checklist for preparing for measurements
In cases where the standard fitting is missing or damaged, tapping the valve is required. To do this, cut the capillary tube, leaving a small tail, and solder a copper adapter to it. This operation requires a torch, solder and flux. Soldering must be carried out quickly so as not to overheat the tube and create burnout.
After physically connecting the hose, open the valve on the pressure gauge. The arrow should move and show the current pressure in the system. If the arrow is at zero or shows vacuum, this may indicate a leak or complete depressurization of the circuit. Normally, when the compressor is turned off, the pressure should equalize and correspond to the ambient temperature.
⚠️ Warning: Never attempt to connect the high pressure hoses (red) to the low pressure ports without adapters. This may lead to rupture of the hose or damage to the pressure gauge due to exceeding the permissible limit.
Pressure standards for various types of refrigerants
Pressure values directly depend on the type of refrigerant used and the ambient temperature. For R134awhich is standard for most modern refrigerators, the operating pressure on the suction side is usually from 0.08 to 0.15 MPa (about 1-2 atm) when the compressor is running. On the discharge side it can reach 1.0-1.2 MPa.
More modern and environmentally friendly isobutane (R600a) operates at lower pressures. Its operating suction pressure is often in the range of 0.04-0.08 MPa. The use of pressure and temperature correspondence tables (PT tables) is mandatory for correct diagnosis. Without them, it is impossible to accurately say whether the pressure in the system is normal.
Below is a table of approximate pressure values for various refrigerants at an ambient temperature of +25°C:
| Refrigerant type | Suction pressure (MPa) | Discharge pressure (MPa) | Boiling point (°C) |
|---|---|---|---|
| R134a | 0.10 - 0.15 | 0.90 - 1.20 | -26.1 |
| R600a | 0.04 - 0.08 | 0.60 - 0.90 | -11.7 |
| R12 (obsolete) | 0.12 - 0.18 | 0.95 - 1.10 | -29.8 |
| R22 | 0.45 - 0.55 | 1.60 - 1.80 | -40.8 |
It is important to understand that these numbers are averaged. Actual indicators depend on the loading of the chambers with products, the temperature in the room and the technical condition of the heat exchangers. Deviation 10-15% from the norm can already be considered a sign of malfunction.
Interpretation of readings: high and low pressure
Analysis of the data obtained allows us to identify a specific malfunction. If the pressure gauge shows pressure too low on the suction side, this may indicate a freon leak, a clogged capillary tube, or a malfunctioning thermostatic valve. In such cases, the compressor runs “idle”, trying to create a vacuum.
Excessively high pressure on the discharge side often indicates contamination of the condenser (radiator on the rear wall) with dust and grease. Also, the cause may be the presence of air in the system or an excess of refrigerant. Air lock significantly increases the condensation pressure, which leads to overload of the compressor.
Let's consider the main symptoms and their possible causes:
- ❄️ Pressure below normal: freon leak, filter drier clogged, faulty expansion valve.
- 🔥 Pressure above normal: condenser dirty, excess refrigerant, air in the system.
- 🔄 Pressure equalizes quickly after stopping: valves are faulty compressor.
If, after turning on the compressor, the pressure gauge needle barely moves and the current consumption is minimal, most likely, the piston group has exhausted its service life. Mechanical failure the internal components do not allow creating the necessary compression. In this case, repair is often impractical.
⚠️ Attention: If you find that the pressure in the system is equal to atmospheric pressure immediately after connection, it means that the refrigerant has completely evaporated. It is strictly forbidden to start a compressor in such a system - it will burn out in a few minutes.
Additional methods for checking the compressor
manometric method; there are other ways to assess the condition of the compressor. One of them is the measurement of current consumption. Ammeterconnected to the power supply circuit will show the real load on the motor. If the current is significantly lower than the rated current, the compressor operates without load (no freon).
If the current is higher than the rated current, this indicates mechanical jamming or inter-turn short circuit of the windings. You can also check the compressor for continuity of the windings with a multimeter in resistance measurement mode. The resistance between the terminals must correspond to the circuit (usually the starting winding has a higher resistance than the working winding).
Testing method with water (only for removed compressors)
If the compressor is removed from the refrigerator, you can lower its pipe into water and turn it on. Air bubbles will indicate the performance of the piston group. However, this method does not provide accurate data on pressure and is applicable only in extreme cases.
Another method is tactile. When a working compressor is operating, the discharge tube should be hot (up to 80-90°C), and the suction tube should be cold, sometimes with frost. If both tubes have the same temperature, circulation it is broken. However, this method is subjective and requires experience.
Comprehensive diagnostics, including measurements of pressure, current and temperature, gives the most complete picture. You should not rely on just one parameter. Combination of factors allows the technician to make an accurate diagnosis and offer an optimal solution to the problem.
Frequently asked questions (FAQ)
Is it possible to check pressure without a pressure gauge?
It is impossible to accurately measure pressure without a pressure gauge. Indirectly, problems with pressure may be indicated by a lack of cold, a hot condenser or freezing of the evaporator, but these signs do not provide the digital values necessary for refilling or repair.
What pressure should be in the switched off refrigerator?
In the switched off and warmed up to room temperature refrigerator, the pressure should be static and correspond to the boiling point of freon at +20...+25°C. For R134a this is approximately 0.5-0.6 MPa. If the pressure is zero, the system is leaky.
Why does the pressure not rise after replacing the compressor?
The reasons may be a clogged capillary tube, a malfunction of the new compressor (rare), improper soldering (narrowing of the tube with solder) or the presence of moisture in the system that has frozen in the capillary.
Is it dangerous to check your blood pressure yourself?
Yes, it is dangerous. High pressure can cause injury, and refrigerants can cause poisoning or fire (especially R600a). Without the skills and equipment, it is better not to carry out such work on your own.
Does the temperature in the room affect the readings of the pressure gauge?
Yes, the pressure of saturated freon vapor directly depends on the temperature. The warmer the room, the higher the static pressure in the system will be before startup. All measurements must be adjusted taking into account the current temperature.