A refrigerator compressor is like a pump: device and principles of operation

Many users, when faced with a breakdown of household appliances, hear from the technicians the phrase that the “pump” has failed. This statement often causes bewilderment, because the refrigerator does not have the usual water pump that pumps liquid. In fact, we are talking about compressor the heart of the refrigeration unit, which in its physical essence is a vacuum pump that forces refrigerant.

Understanding that the compressor works exactly like a piston or linear pump allows you to better understand the causes of noise, insufficient cooling or complete failure device. Refrigerant (freon) circulates in a closed circuit, changing its state of aggregation, but the driving force of this process is the compression unit. Unlike water pumps, here we are dealing with high-pressure gases.

In this article we will take a closer look at why it is technically correct to compare this unit with a pump, how exactly it works and what factors affect its durability. You will learn how pressure inside the system depends on the health of the piston group and why it is important to monitor the condition of the oil.

Physical essence: why a compressor is called a pump

From the point of view of thermodynamics and mechanics, a refrigerator compressor performs the function of a pump, since it forcibly moves the working fluid (gas) from a low pressure zone to a high pressure zone. In the everyday mind, a pump is associated with water, but in physics it is a device for moving liquids and gases. In the refrigerator freon in a gaseous state, it is sucked in through the suction pipe.

The mechanism compresses the gas, increasing its temperature and pressure, and then pushes it into the condenser (heat exchanger on the back wall). This process is identical to how a bicycle pump works: when you inflate a tire, the piston compresses the air and it becomes hot. It behaves in the same way refrigerant inside the sealed motor casing.

• 🌀 Suction: Gaseous freon is drawn from the evaporator, where it takes away heat from the products.
• 🔥 Compression: A piston or plate reduces the volume of the chamber, sharply increasing the gas pressure.
• 💨 Pumping: The compressed hot gas is pushed into the condenser to cool.

It is important to understand that the system is hermetically sealed, and the amount of substance in it is constant. The compressor does not create cold, it only “pumps” the coolant, transferring heat from the inner chamber to the outside. If this “pump” stops, the heat exchange cycle is interrupted, and the temperature inside begins to rise.

Compressor design: internal mechanics

Visually, the compressor is a black metal “tank”, but a complex mechanism is hidden inside. Most household refrigerators use piston units that operate on the principle of reciprocating motion. The electric motor rotates the crankshaft, which drives the pistons.

There are also inverter linear models, where the piston moves without a rotational mechanism, due to direct electromagnetic action. However, the “pump” principle remains the same: there is an expansion chamber and a compression chamber. All moving parts are washed with special oil, which is also located in a sealed housing.

⚠️ Attention: Opening the compressor casing at home is strictly prohibited. Inside there is freon under pressure, and moisture or dust getting inside the mechanism will instantly disable the “pump”, making it unrepairable.

The key elements of the internal structure are valves. They work like check valves in any pump, allowing gas to flow in only one direction. If valve group is worn out, the compressor will push gas back and forth without creating the necessary pressure drop, and the refrigerator will stop freezing.

Refrigerant circulation: the role of the pump in the circuit

For the refrigerator to work efficiently, the “pump” must create sufficient pressure difference. At the outlet of the compressor, the pressure can reach 15-20 atmospheres, and at the inlet it can be close to vacuum. It is this difference that makes freon circulate at the required speed.

Passing through the condenser, the gas cools and turns into liquid. Then, passing through the capillary tube (throttle), the pressure drops sharply, and the liquid boils in the evaporator, turning into gas. The compressor sucks in this gas again. If the pump power drops, the cycle is disrupted: the freon does not have time to boil or, conversely, does not have time to condense.

In systems with No Frost the requirements for compressor performance are higher, since it is necessary to pump gas through more complex air channels and evaporators. A weak compressor will not be able to provide the required flow, which will lead to the formation of a “snow coat” and overload the engine.

• 📉 Low pressure at the inlet may indicate a freon leak or capillary blockage.
• 📈 High pressure at the outlet often indicates airing of the system or contamination capacitor.
• 🔇 No sound pump operation when the light is on indicates an open circuit or a wedge in the mechanism.

Diagnostics of the system is often based on measuring current consumption and pressure in the circuit. If the current is normal, but there is no cold, perhaps the “pump” has simply lost performance due to wear of the piston group.

Types of compressors: evolution of pumping technologies

Technologies for creating “refrigeration pumps” have been developing for decades. The most common are classic piston models. They are reliable, but they create vibration and noise due to rotating masses and the reciprocating movement of the piston.

More modern inverter compressors operate on the principle of changing the engine speed. They do not turn off completely, but only slow down, maintaining the temperature. This reduces wear on the mechanical parts of the “pump” and saves energy.

Linear compressors, often found in technology LG i Whirlpool, lack rotational motion, which theoretically reduces friction. However, their repair is often not economically feasible due to the high complexity and cost of spare parts.

Symptoms of a compressor malfunction pump

Understanding that a compressor is a pump helps diagnose problems more quickly. If the “pump” does not pump, the system stops. One of the first signs is a change in the nature of the sound of the operation. The appearance of a metallic clanging, buzzing or knocking indicates mechanical destruction of internal components.

Another symptom is a hot case. Normal operation of the pump is accompanied by heating, but if the casing is hot to the point where it cannot be touched, this is a signal of overload or problems with heat dissipation. The thermal relay may also be triggered, and the motor will constantly click and try to start.

⚠️ Attention: If the compressor hums but does not start, and you can hear the relay clicking, do not try to start it repeatedly. This can lead to burning of the electric motor windings.

It becomes a frequent occurrence hydraulic hammer. This happens if too much liquid freon or oil enters the compressor cylinder. Liquid, unlike gas, does not compress, which leads to instant destruction of the valves or piston. This is an analogue of water hammer in water pumps.

Performance testing is often carried out by a technician by connecting a pressure gauge station. If the discharge pressure does not increase and the suction pressure does not fall, the compressor is “dead” mechanically.

Features of replacement and diagnostics

Replacing a compressor is a complex technical operation that cannot be performed without special equipment. Since the system is sealed, replacing the “pump” requires opening the circuit, which is accompanied by the release of residual freon.

The process includes dismantling the old unit, installing a new one, soldering connections, evacuation of the system (removing air and moisture with a vacuum pump) and charging with new refrigerant. Evacuation - a critical stage: if left in the system moisture, it will freeze in the capillary and block the operation of the new compressor.

It is important to select an analogue strictly according to the characteristics: power, refrigerant (R600a or R134a) and type of oil. Installing a more powerful pump can lead to freezing of the evaporator, and a weak one can lead to insufficient cooling.

Frequently asked questions (FAQ)