Operating Principle and Standard Installation Steps of Multi - split Systems in Refrigerant Air - conditioning Systems

The multi - connected unit, commonly known as "one - to - multiple", refers to a system where one outdoor unit is connected to two or more indoor units through pipes.

The outdoor side uses air - cooled heat exchange, and the indoor side uses direct - evaporation heat exchange. The multi - connected unit is a primary refrigerant air - conditioning system. It uses refrigerant as the transportation medium. The outdoor main unit consists of an outdoor heat exchanger, a compressor, and other refrigeration accessories. The terminal device is an indoor unit composed of a direct - evaporation heat exchanger and a fan.
The multi - connected unit system has many advantages such as energy - saving, comfort, and stable operation.

Moreover, each room can be adjusted independently to meet the different air - conditioning load requirements of different rooms.
In order to achieve the goal of energy - saving, the multi - connected unit realizes the variable - capacity operation of the compressor and the system through the effective control of the refrigeration medium flow rate.
Currently, the mature technologies include:

Variable - frequency multi - connected unit technology: Variable - frequency multi - connected unit technology refers to the way the outdoor main unit of a single - pipeline one - to - multiple space heat pump system adjusts its output capacity. The outdoor main unit adjusts the number of operating compressors according to the change of indoor air - conditioning load, so that the motor power corresponds to the load change. By changing the input frequency of the variable - frequency compressor through the variable - frequency device, the rotational speed of the compressor is changed. The two cooperate to achieve linear adjustment of cooling capacity and energy. In addition, the change of indoor temperature is regulated by the electronic expansion valve.

Digital scroll multi - connected unit technology: Digital scroll technology has a unique performance called "axial flexibility". This performance allows the fixed scroll plate to move a small amount axially, ensuring that the fixed scroll plate and the moving scroll plate are always jointly loaded with the optimal force. The optimal force that combines the two scroll plates under various operating conditions ensures the high efficiency of digital scroll technology.
Digital scroll operation is divided into two stages: the "load state", in which the solenoid valve is normally closed; and the "unload state", in which the solenoid valve is open. In the load state, the compressor works like a conventional scroll compressor, delivering the full capacity and refrigerant mass flow rate. [Source: Refrigeration Encyclopedia]. However, in the unload state, no capacity and refrigerant mass flow rate pass through the compressor. Variable - capacity refrigerant control is achieved through the periodic loading and unloading of the compressor. Digital scroll technology started relatively late in China, and the technology is not yet very mature.