Requirements for the installation and connection of indoor and outdoor units of VRF air conditioning systems
VRF (Variable Refrigerant Flow) air conditioning systems have high installation requirements , and specific parameters vary between brands. The following are general and critical installation and connection requirements; please refer to your brand's official installation manual for specific values .
I. Outdoor Unit Installation
Space and Spacing : Sufficient air intake, exhaust, and maintenance space must be ensured. When multiple outdoor units are arranged side by side, a spacing of at least 25mm must be maintained , and it is recommended that no more than 3 units be arranged side by side.
Foundation and Fixation : The foundation must be able to withstand the weight of the machine and must be firmly fixed (such as with anchor bolts) to prevent it from tipping over due to strong winds or earthquakes.
Location Selection : Installation in areas with a risk of flammable gas leaks is strictly prohibited . If installed in an enclosed or confined space, measures must be taken to prevent asphyxiation due to refrigerant leaks.
II. Indoor Unit Installation
Vibration prevention and leveling : The mounting base or bracket must be firm and reliable to ensure that the indoor unit is level and to prevent vibration or water leakage during operation.
Maintenance space : Sufficient maintenance access must be provided on one side of the electrical box or in a designated location to facilitate future maintenance.
III. Refrigerant Piping Connection
This is the core of the VRF air conditioning system , and the requirements are the most stringent.
Material selection : Seamless copper pipes deoxidized with phosphate must be used . The pipe diameter and wall thickness must strictly comply with the design requirements; for example, the wall thickness of a Φ9.52mm pipe is usually not less than 0.8mm.
Three principles for construction : The pipeline must be dry, clean, and airtight . Prevent water from entering before installation; after installation, it must be blown clean and vacuum dried.
Welding protection : Nitrogen gas must be introduced for protection when welding copper pipes (the recommended pressure is usually about 0.2 kgf/cm²) to prevent the formation of oxide scale inside. After welding, the nitrogen gas should be turned off only after the copper pipe has cooled down.
Manifold installation : Manifolds specified by the manufacturer must be used. Manifolds can only be installed horizontally or vertically , and a certain distance must be maintained between manifolds and between manifolds and elbows (e.g., at least 18 inches/approximately 457 mm).
Insulation : The refrigerant pipes must be adequately insulated. The insulation material must be able to withstand high temperatures (at least 70°C for liquid pipes and at least 120°C for gas pipes in heat pump systems), and the joints must be sealed without gaps.
IV. Pipeline Length and Elevation Difference
VRF air conditioning systems have strict limitations on pipe length; exceeding these limits will result in a significant reduction in cooling/heating performance.
Piping length : includes the maximum total piping length (e.g., 300m), the actual maximum piping length (e.g., 120m), and the length limit from the first branch pipe to the last indoor unit (e.g., 40m).
Height difference : The maximum height difference between the outdoor unit and the indoor unit is usually limited to 50m (outdoor unit on top) or 40m (outdoor unit on the bottom). The height difference between indoor units is usually limited to within 15m .
V. Electrical Connections
Power and Communication : An independent power supply must be used , and the power cord specifications must meet the requirements. Communication lines typically use shielded twisted-pair cables and must be connected in a daisy-chain configuration ; star or branched connections are strictly prohibited.
Grounding : Reliable grounding is required. It is strictly forbidden to connect the ground wire to water pipes, gas pipes, or lightning rods.
VI. Airtightness, Vacuuming and Refrigerant Charging
Air tightness test : The system must be subjected to a nitrogen pressure test to check for leaks at all solder joints and connections.
Vacuuming : A vacuum pump must be used to thoroughly evacuate the system from the valve ports of the liquid and gas lines to remove air and moisture.
Refrigerant charging : The outdoor unit is usually pre-charged with some refrigerant, but additional charging must be done based on the actual length and diameter of the liquid line on site . The amount to be added must be calculated strictly according to the formula (usually based on the length of the liquid line).
These requirements are interconnected, and it is recommended to carefully read and follow the complete installation manual provided by your brand before construction.
