A Basic Overview of Variable Refrigerant Flow

A Basic Overview of Variable Refrigerant Flow

Variable refrigerant flow technology was invented by Japanese company Daikin in 1982, where it was launched commercially. This name is still being used today by heating and air conditioning companies in Orlando and the rest of the world. Here’s some basic information on variable refrigerant flow.


Conventional Multi Split System


The conventional multi split direct expansion (DX) system sources its cooling or heating medium from refrigerant. The system is comprised of an outdoor unit containing one or more compressors. These compressors are connected to several indoor units. Normally, the compressors are configured with a binary ON/OFF switch. The switch is usually at a fixed speed rotation or is shut down entirely. Only one or more compressors can vary the capacity of the system. The DX system is normally not efficient when operating at a less than optimal load. For example one compressor must be turned on if only one indoor fan coil unit is in need of cooling in order to provide the necessary cooling.


Capacity Control


Several systems utilize DC inverter compressors in order to control the capacity by affecting the refrigerant volume being sent out by the compressor. Normally, these compressors are found on the outdoor unit. There are usually one or more compressors that are built into a high capacity system. Some system are available in a combination of non-inverter and inverter compressors used within the system. In certain designs, outdoor units can potentially be linked together in order to send out greater capacity to indoor units. The algorithm controlling this process is relatively complex; strong processors are used in conjunction with powerful modules in order to provide the compressors with enough drive. In terms of speed, the compressors can be stepped up or down depending on the load requirements. The load requirements themselves are based on the system’s saturation temperatures. In the case that a lower load is required, the rotation will be lower. For instance, if the compressors are made to run for 25 Hz to 100 Hz with each individual step having a 5 Hz increment, there will ultimately be 8 steps that the compressors can run. The system is highly efficient through the compressor’s ability to vary vapor compression. This is true despite the frequent changes of cooling or heating requirements.


DC Fan Motors


DC fan motors are normally used in indoor and outdoor units to monitor fan speed. Changing the speed of the fans depending on load requirements further improves energy savings and system efficiency. Normal systems use conventional permanent split capacitor fan motors which can only operate on certain speeds such as super high, high, medium, low, and ultra low. Ultimately, these characteristics contribute to the relatively high power that variable refrigerant flow brings to the system.



Find Out More