"Ten Forbidden Zones" and Precautions for Variable Refrigerant Flow (VRF) System Installation
2025-04-19
I. Ten Forbidden Zones for the Installation of Variable Refrigerant Flow (VRF) System Projects
1.1 It is prohibited to supply power to indoor units of the same system in a non-unified manner.
1.2 It is prohibited to use carbon tetrachloride to clean the pipeline.
1.3 It is prohibited to weld the pipeline without nitrogen protection.
1.
1.5 It is prohibited to use "copper-aluminum connecting pipes" instead of copper pipes for the installation of the air conditioning system.
1.6 It is prohibited to insulate the vapor-liquid two-phase pipeline together.
1.7 It is prohibited to install the outdoor unit in a place with poor air supply and return.
1.8 It is prohibited to install the VRF system in places such as machine rooms.
1.9 It is prohibited to bundle the control line (communication line) and the power line (high voltage) together.
1.10 It is prohibited to select cables without following the wire diameter requirements in the technical manual.
1.1 It is prohibited to supply power to indoor units of the same system in a non-unified manner.
1.2 It is prohibited to use carbon tetrachloride to clean the pipeline.
1.3 It is prohibited to weld the pipeline without nitrogen protection.
1.
1.5 It is prohibited to use "copper-aluminum connecting pipes" instead of copper pipes for the installation of the air conditioning system.
1.6 It is prohibited to insulate the vapor-liquid two-phase pipeline together.
1.7 It is prohibited to install the outdoor unit in a place with poor air supply and return.
1.8 It is prohibited to install the VRF system in places such as machine rooms.
1.9 It is prohibited to bundle the control line (communication line) and the power line (high voltage) together.
1.10 It is prohibited to select cables without following the wire diameter requirements in the technical manual.
II. Installation of the Outdoor Unit
① Selection of the installation location of the outdoor unit: The outdoor unit of the air conditioner must be more than one meter away from the wall to ensure heat dissipation and have sufficient maintenance space. Place shock-absorbing pads at the installation holes and stress points where the outdoor unit contacts the foundation, and fix it with nuts.
① Selection of the installation location of the outdoor unit: The outdoor unit of the air conditioner must be more than one meter away from the wall to ensure heat dissipation and have sufficient maintenance space. Place shock-absorbing pads at the installation holes and stress points where the outdoor unit contacts the foundation, and fix it with nuts.
III. Installation of the Indoor Unit
① Fabrication and selection of the hanging codes: After determining the length of the suspension rod according to the hoisting height of the indoor unit and the floor height, cut the material.
② Installation of the indoor unit
a. Make marks and drill holes with an electric drill. The hoisting position of the indoor unit should ensure that the air conditioning condensate water can be drained, the air duct can be installed conveniently, and the air supply is smooth.
b. Full-threaded suspension rods must be used, and the indoor unit should be fixed with double nuts to ensure that the machine is firmly hung. After the indoor unit is hung, it must be adjusted to be horizontal.
c. When installing the throttling component, it must be installed vertically upward and horizontally. Tilt and inversion are prohibited, and pay attention to the connection direction during connection.
d. Wrap the indoor unit with a dust-proof cover to prevent a large amount of dust from entering the machine and affecting the operation effect of the machine. Ensure that there is sufficient installation and maintenance space around the indoor unit and a reasonable air supply and return airflow organization.
① Fabrication and selection of the hanging codes: After determining the length of the suspension rod according to the hoisting height of the indoor unit and the floor height, cut the material.
② Installation of the indoor unit
a. Make marks and drill holes with an electric drill. The hoisting position of the indoor unit should ensure that the air conditioning condensate water can be drained, the air duct can be installed conveniently, and the air supply is smooth.
b. Full-threaded suspension rods must be used, and the indoor unit should be fixed with double nuts to ensure that the machine is firmly hung. After the indoor unit is hung, it must be adjusted to be horizontal.
c. When installing the throttling component, it must be installed vertically upward and horizontally. Tilt and inversion are prohibited, and pay attention to the connection direction during connection.
d. Wrap the indoor unit with a dust-proof cover to prevent a large amount of dust from entering the machine and affecting the operation effect of the machine. Ensure that there is sufficient installation and maintenance space around the indoor unit and a reasonable air supply and return airflow organization.
IV. Installation of the Support for the Construction of the Refrigerant Pipe
The distance between the installation frames of the support should not be too large, and the installed supports must be arranged neatly.
② Installation of the Refrigerant Pipe Laying
a. Cut the copper pipe of the corresponding specification and length with a cutter.
b. Clean the burrs at the pipe ends and the copper chips inside the pipe.
③ Protection of the Refrigerant Pipe
a. If the pipe cannot be connected to the outdoor unit in time, it must be sealed to prevent the intrusion of dust, moisture, etc.
b. When the pipe passes through the wall, a casing must be added and sealed for protection in time.
④ Installation of the Branch Pipe
a. The branch pipe cannot be replaced by a tee and can only be installed horizontally or vertically.
b. The horizontal straight pipe section between the elbow of the copper pipe and the adjacent branch pipe is ≥1M.
c. The distance between the horizontal straight pipe sections of two adjacent branch pipes is 1M.
d. The distance of the horizontal straight pipe section of the indoor unit connected after the branch pipe is ≥0.5M.
⑤ Expansion Joint Connection: For the connection of refrigerant pipes with copper pipe diameters, it is recommended to use the expansion joint method, and it is prohibited to use the flared connection method.
⑥ Flaring
a.
b. When connecting with nuts, two adjustable wrenches must be used for operation.
⑦ Nitrogen Charging Welding of the Refrigerant Pipe
a. To ensure construction safety, a pressure reducing valve needs to be connected to the nitrogen cylinder, and the nitrogen pressure during welding should be controlled at 0.2-0.3KGF/CM2.
b. Determine the nitrogen path, insert the nitrogen pipe into the inlet of the refrigerant pipe to be welded and seal it. Open the valve of the nitrogen cylinder, adjust the nitrogen gas flow through the pressure reducing valve, and finally carry out the welding.
⑧ Air Tightness Test of the Refrigerant Pipe: Connect the vapor and liquid pipes together, lead out a connection pressure gauge, and seal and weld this interface. Use 28KG/CM nitrogen to maintain the pressure for R22 (40KGF/CM2 for the R410A system). Pay attention to the pressure correction before and after the pressure test. There will be a pressure change of +0.1KGF/CM2 for every +1°C. Record both the temperature during the pressure test and the confirmed temperature.
⑨ Cleaning of the Refrigerant Pipe by Blowing: In principle, blow the dirt from top to bottom or horizontally, with a blowing pressure of 5KG/CM2 to ensure that there are no impurities in the system.
Use the following method to blow the dirt:
a. Hold a suitable blocking material against the main gas side pipe opening of the indoor unit;
b. Gradually pressurize the inside of the pipe with nitrogen. When the pressure increases to the point where it cannot be resisted, suddenly release the pipe opening;
c. Repeat steps a and b for repeated dirt blowing.
⑩ Insulation Patching of the Refrigerant Pipeline
a. Cut the insulation material larger than the gap with a paper cutter, and apply glue to the end face of the insulation pipe.
b. Pull the two ends apart, embed the insulation material, and stick the joint with glue.
The distance between the installation frames of the support should not be too large, and the installed supports must be arranged neatly.
② Installation of the Refrigerant Pipe Laying
a. Cut the copper pipe of the corresponding specification and length with a cutter.
b. Clean the burrs at the pipe ends and the copper chips inside the pipe.
③ Protection of the Refrigerant Pipe
a. If the pipe cannot be connected to the outdoor unit in time, it must be sealed to prevent the intrusion of dust, moisture, etc.
b. When the pipe passes through the wall, a casing must be added and sealed for protection in time.
④ Installation of the Branch Pipe
a. The branch pipe cannot be replaced by a tee and can only be installed horizontally or vertically.
b. The horizontal straight pipe section between the elbow of the copper pipe and the adjacent branch pipe is ≥1M.
c. The distance between the horizontal straight pipe sections of two adjacent branch pipes is 1M.
d. The distance of the horizontal straight pipe section of the indoor unit connected after the branch pipe is ≥0.5M.
⑤ Expansion Joint Connection: For the connection of refrigerant pipes with copper pipe diameters, it is recommended to use the expansion joint method, and it is prohibited to use the flared connection method.
⑥ Flaring
a.
b. When connecting with nuts, two adjustable wrenches must be used for operation.
⑦ Nitrogen Charging Welding of the Refrigerant Pipe
a. To ensure construction safety, a pressure reducing valve needs to be connected to the nitrogen cylinder, and the nitrogen pressure during welding should be controlled at 0.2-0.3KGF/CM2.
b. Determine the nitrogen path, insert the nitrogen pipe into the inlet of the refrigerant pipe to be welded and seal it. Open the valve of the nitrogen cylinder, adjust the nitrogen gas flow through the pressure reducing valve, and finally carry out the welding.
⑧ Air Tightness Test of the Refrigerant Pipe: Connect the vapor and liquid pipes together, lead out a connection pressure gauge, and seal and weld this interface. Use 28KG/CM nitrogen to maintain the pressure for R22 (40KGF/CM2 for the R410A system). Pay attention to the pressure correction before and after the pressure test. There will be a pressure change of +0.1KGF/CM2 for every +1°C. Record both the temperature during the pressure test and the confirmed temperature.
⑨ Cleaning of the Refrigerant Pipe by Blowing: In principle, blow the dirt from top to bottom or horizontally, with a blowing pressure of 5KG/CM2 to ensure that there are no impurities in the system.
Use the following method to blow the dirt:
a. Hold a suitable blocking material against the main gas side pipe opening of the indoor unit;
b. Gradually pressurize the inside of the pipe with nitrogen. When the pressure increases to the point where it cannot be resisted, suddenly release the pipe opening;
c. Repeat steps a and b for repeated dirt blowing.
⑩ Insulation Patching of the Refrigerant Pipeline
a. Cut the insulation material larger than the gap with a paper cutter, and apply glue to the end face of the insulation pipe.
b. Pull the two ends apart, embed the insulation material, and stick the joint with glue.
V. Installation of the Condensate Pipe
① The installation of the condensate pipe should ensure a slope of 1/100.
② When setting the vent, two elbows must be added to make the exhaust port face downward to prevent dust and other dirt from falling into the pipe and blocking the pipeline.
③ The horizontal exhaust pipe must avoid the phenomenon of head-on collision to prevent poor drainage.
④ For the model with a lifting pump, the height of the lifting pipe should not exceed the maximum value specified by the equipment, and a vent should not be set in the lifting section.
⑤ The support interval of the horizontal pipe is generally 0.8-1.2m and should not be too large, otherwise, deflection will occur and an air pocket will be formed.
⑥ For the indoor unit with a large negative pressure at the drainage port of the water collecting tray, a water seal elbow must be installed on the drainage pipe. After the installation is completed, a full water flow test must be carried out.
① The installation of the condensate pipe should ensure a slope of 1/100.
② When setting the vent, two elbows must be added to make the exhaust port face downward to prevent dust and other dirt from falling into the pipe and blocking the pipeline.
③ The horizontal exhaust pipe must avoid the phenomenon of head-on collision to prevent poor drainage.
④ For the model with a lifting pump, the height of the lifting pipe should not exceed the maximum value specified by the equipment, and a vent should not be set in the lifting section.
⑤ The support interval of the horizontal pipe is generally 0.8-1.2m and should not be too large, otherwise, deflection will occur and an air pocket will be formed.
⑥ For the indoor unit with a large negative pressure at the drainage port of the water collecting tray, a water seal elbow must be installed on the drainage pipe. After the installation is completed, a full water flow test must be carried out.
VI. Insulation Installation of the Pipeline System
The insulation material for the refrigerant pipeline should be a closed-cell foamed insulation material, a flame-retardant class B1 material with a heat resistance exceeding 120°C. When the outer diameter of the copper pipe D≤12.7MM, the thickness of the insulation layer ＆=15MM or more; when the outer diameter of the copper pipe D≥15.88MM, the thickness of the insulation layer ＆=20MM or more. The condensate pipe should be insulated with a flame-retardant class B1 rubber-plastic insulation cylinder, and the thickness of the insulation layer is usually 10MM. The pipeline must be sleeved when passing through the wall.
The insulation material for the refrigerant pipeline should be a closed-cell foamed insulation material, a flame-retardant class B1 material with a heat resistance exceeding 120°C. When the outer diameter of the copper pipe D≤12.7MM, the thickness of the insulation layer ＆=15MM or more; when the outer diameter of the copper pipe D≥15.88MM, the thickness of the insulation layer ＆=20MM or more. The condensate pipe should be insulated with a flame-retardant class B1 rubber-plastic insulation cylinder, and the thickness of the insulation layer is usually 10MM. The pipeline must be sleeved when passing through the wall.
VII. Installation of the Signal Line
① A dedicated power supply line must be set. The allowable fluctuation range of the power supply voltage is ±10% of the rated voltage; the power supply capacity must be sufficient, the cable wire diameter meets the requirements, and there is a corresponding open-circuit protection device; the grounding system must be reliable. If the outdoor unit of the air conditioner is installed at the highest point of the building, pay attention to lightning protection treatment;
② The signal line must use a three-core shielded wire, and the shielding layer of the signal line must be connected to the sheet metal grounding of the electrical control box.
① A dedicated power supply line must be set. The allowable fluctuation range of the power supply voltage is ±10% of the rated voltage; the power supply capacity must be sufficient, the cable wire diameter meets the requirements, and there is a corresponding open-circuit protection device; the grounding system must be reliable. If the outdoor unit of the air conditioner is installed at the highest point of the building, pay attention to lightning protection treatment;
② The signal line must use a three-core shielded wire, and the shielding layer of the signal line must be connected to the sheet metal grounding of the electrical control box.
VIII. Vacuum Drying
The vacuum must be pumped simultaneously from both the vapor and liquid sides; the ultimate vacuum degree of the vacuum pump should reach -756MMHG or below, and its exhaust volume should reach 4 liters/second or more; a check valve must be added to the vacuum pump used for the R410A system, or a vacuum pump with a check valve should be used.
The vacuum must be pumped simultaneously from both the vapor and liquid sides; the ultimate vacuum degree of the vacuum pump should reach -756MMHG or below, and its exhaust volume should reach 4 liters/second or more; a check valve must be added to the vacuum pump used for the R410A system, or a vacuum pump with a check valve should be used.
IX. Refrigerant Refilling
Calculate the refrigerant refilling amount through the formula according to the actual size and length of the liquid pipe, and record the refilled refrigerant amount in the refrigerant refilling table of the outdoor unit; it is absolutely not allowed to estimate the refrigerant amount by measuring the operating current, pressure, etc.
Calculate the refrigerant refilling amount through the formula according to the actual size and length of the liquid pipe, and record the refilled refrigerant amount in the refrigerant refilling table of the outdoor unit; it is absolutely not allowed to estimate the refrigerant amount by measuring the operating current, pressure, etc.
X. Debugging
Confirm whether the number of connected indoor units is consistent with the number displayed on the digital tube of the outdoor unit; start the machine and check whether the drainage is smooth, whether there are any faults on the electrical control board of the indoor unit, and whether the operating current of the unit and the inlet and outlet air temperatures are within the allowable range.
Confirm whether the number of connected indoor units is consistent with the number displayed on the digital tube of the outdoor unit; start the machine and check whether the drainage is smooth, whether there are any faults on the electrical control board of the indoor unit, and whether the operating current of the unit and the inlet and outlet air temperatures are within the allowable range.
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