The operation logic of the VRF is fully built-in inside the system and is proprietary for each VRF manufacturer. The system gets inputs from the user (e.g. desired comfort temperature) and from the surroundings (outside ambient temperature), and according to that data it implements its logic in order to get to the desired comfort conditions, utilizing optimal power consumptions.
The ability to adjust itself to the outdoor conditions is one of the main factors that makes these systems so efficient, compared to the traditional water cooled systems, based on chillers and fan coils.
Now, let’s dive in, and see how it works in details. Let’s take as an example a typical VRF installation, with one outdoor unit and multiple indoors.
At the beginning, the system is in standstill condition (everything is turned off).
Once a user turns one of the indoors "ON" by its local remote, the outdoor “gets noted” regarding it, and starts working. At this point, it will examine the outdoor conditions (temperature), the operating indoor requirements (operation mode, set point temperature), and will operate the compressor at the exact level, required to comply with the indoor requirements.
When another indoor unit is turned on, the outdoor recalculates the requirements from all the indoors, and will increase the compressor’s output, according to the required level of demand.
This process is constantly occurring with any change, performed in the HVAC system. As described, this system is fully automatic, and regulates its power consumption based on the demand arriving from the indoor units and outside prevailing conditions. User can have influence on the desired indoor comfort conditions, modifying: Operation mode (on/off), Operation state (Cool/Heat/Fan/Dry/Auto), set point temperature, fan speed (high/medium/low/auto). Controlling those parameters is the only thing required for proper operation, and the only thing that is required for proper integration with the VRF system.