Digital Scroll Compressors: The complete guide

The Digital Scroll compressor utilizes “Axial Flex” technology, which allows the scroll disk to move a very small distance in the axial direction, ensuring that the disk always works with optimum force.

Working Principle

How Digital Scroll compressors work

Digital scroll compressor technology utilizes an unloading mechanism that allows for capacity adjustment within the compressor. This mechanism is known as pulse width modulation (PWM). It is achieved by opening and closing a solenoid valve which moves the fixed scroll periodically along the vertical axis.

It switches the compressor to the no-load state. As a result, no compression occurs during the unloading of the digital scroll compressor. Typically, it takes about 20 seconds to complete a Digital Scroll compressor’s unloading and loading cycle.

In the load state, the compressor is running at full load. Furthermore, unloading a digital scroll compressor reduces its capacity, which may vary between 10 and 90%. During the no-load period, the compressor can cool down a little, thus allowing it to run continuously.

Features of the Digital Scroll compressor

“When the solenoid valve is opened, the fixed scroll disc moves upward; the compressor capacity is zero, no refrigerant flow through, the compressor does not do work on the refrigerant, this process is called “unloading state”; the fixed scroll disc returns to the original position of engagement When the solenoid valve is closed, and the fixed scroll disc is engaged, the compressor capacity is 100%, and all refrigerant flows through the compressor, and the compressor does work on the refrigerant.

Advantages and disadvantages of digital scroll compressor


A digital scroll compressor can adjust the capacity of the air it is compressing. Thus, it allows for better capacity control.

The digital scroll compressor unloading mechanism helps to dissipate some heat. Therefore, the digital compressor is more efficient because it can maintain a constant operating temperature without shutting down.

The output is controlled by variable analog signals for more precise temperature control. This feature is critical for any air conditioning and refrigeration application.


Digital scroll compressors are not energy efficient if we consider their power consumption. They provide less output than regular compressors. However, it consumes power even when it is at no load. Therefore, a huge amount of power is wasted when the compressor runs at 10% or 20% of its minimum capacity.

Scroll compressors are known for their quiet operation. However, the unloading mechanism of larger digital scroll compressors can produce audible noise in the machine. Therefore, it may not be suitable for certain applications, such as medical, library, and home HVAC systems, where noiseless operation is a priority.

Therefore, even though it has some unique privileges, it may not be the first choice for all scenarios.

 Digital Scroll Compressor vs. Conventional Scroll Compressor and Inverter Scroll Compressor

Conventional scroll compressor

Digital scroll compressor technology is a bit more complex than a regular scroll compressor. However, the basic compression mechanism is the same, and it consists of two interwoven scrolls. Let’s take a look at the fundamental differences between digital scroll compressors and conventional scroll compressors.

Operating cycle and speed

Conventional scroll compressors are fixed-speed compressors. They will run at full speed for some time and then shut down to cool down. In contrast, digital scroll compressor technology is more complex. They typically have a cycle time of about 20 seconds when switching between full speed and deceleration. However, unlike conventional compressors, they do not need to be shut down.

Operating temperature

Digital scroll compressors provide effective temperature control both inside the compressor and in the cooling system. A conventional scroll compressor will discharge air that is running at full load. When it gets hot, it will shut down completely to cool down and start up again after a specified time. As a result, the temperature is not constant and fluctuates constantly.

Compressor Capacity

Digital scroll compressors run at full capacity for some time and reduced capacity for the remainder of a cycle. This allows for better control of the machine’s output capacity. However, conventional scroll compressors do not have control over their capacity.

Power Consumption

Digital scroll compressors are less efficient than conventional scroll compressors. They require more power to provide the same output as a conventional compressor. Despite the high power consumption, digital scroll compressors are more efficient in cooling.

Operating Noise

Conventional scroll compressors are usually very quiet. However, the digital scroll compressor unloading mechanism generates additional noise during operation. Therefore, it is not well suited for quiet environments.

Inverter scroll compressors

Digital scroll compressor technology is very similar to inverter technology, as they both use modulation mechanisms. Digital scroll compressors are called variable capacity compressors (VCC). Inverter compressors are called variable speed compressors (VSC).

They both provide excellent control of capacity and temperature. However, they also have some significant differences. We have highlighted their differences below.

Modulation Technology

Digital compressors modulate capacity, while variable speed compressors modulate speed. The digital scroll compressor motor is always running, and it just uses the unloading mechanism to bypass the air. At the same time, the inverter compressor reduces its speed to reduce its capacity.

Oil Return Considerations

The oil return efficiency of digital scroll compressors is better than that of inverter scroll compressors. This is because the motor is always running at a constant speed. However, inverter compressors reduce the motor speed, so it is necessary to consider oil return.

Operating Noise

Inverter compressors are as quiet as regular scroll compressors. Therefore, they are very popular in air conditioning applications. However, due to their unloading mechanism, digital scroll compressors can generate noise during operation.

Problems to be noted with digital scroll compressors

1.the skewed perspective of the compressor installation must not exceed 5 degrees; the factory nameplate of the compressor indicates consistent grease; ensure that the power supply system switch power and the main parameters of the compressor factory nameplate are consistent, the compressor is internally filled with dry manic N² at the factory, and the internal working pressure of the compressor should be released before docking.

2. the refrigeration unit leak detection and compressor work, the larger working pressure can not exceed the working pressure required on the compressor factory nameplate. You cannot use gas to try to run the compressor because the high-pressure gas is mixed with oil, and the mixed high-pressure vapor is likely to explode because of the high temperature of the vortex outlet, and then cause the destruction of the compressor.

3.Before running the compressor, check whether the automatic exhaust valve is open. It is very critical to open the automatic exhaust valve thoroughly before running the compressor; if the exhaust valve is not fully opened, the compressor will cause the risk of high pressure and high temperature during the start-up process.

4.The system software is larger to disconnect the working pressure not more than 28bar, and it is proposed that the high pressure should be manually calibrated again after disconnection to facilitate complete fault detection, and the low-pressure switch disconnection preset value is not allowed to be less than 0.1bar.

5.Do not mix grease, mineral oil, or alkyl benzene. R404A compressor is applied with POE-generated grease oil, and the R22 compressor is applied with 3GS mineral oil. The compressor factory nameplate indicates the original amount of oiling before leaving the factory, and the amount added on the spot can be 100ml less than the original amount added.

6.pipeline electric welding, be sure to maintain the pipeline internal nitrogen flush to avoid causing oxidation skin blocking system software, electric welding all copper and silver alloy welding materials can be applied better with 45% silver electrode, get better is the quality of laser welding. Propose electric welding breathing and exhaust pipe, with a wet rag tied up, and then carry out electric welding.

7.compressor operation can not create a pressure difference or when running loud sound. Maybe the compressor U, V, and W three-phase wiring are incorrect; you must swap two lines.


Although the digital scroll compressor is at the application level, not as much as the DC inverter compressor nowadays, its function is not ordinary. It has the same energy-saving effect as DC inverter compressors. However, digital scroll compressors are often used in multi-connector equipment, and the results are not lacking. Nowadays, air conditioning systems are developing rapidly, and digital central air conditioners are also becoming popular in the market. Perhaps soon, we will see the scene of a duo of inverter central air conditioners and digital central air conditioners.


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