DC Inverter Multi VRF System   
 
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4.4 Vacuum Pumping, Refrigerant Adding 
4.4.1 Vacuum Pumping 
(1) Outdoor  unit  has  been  charged  with  refrigerant  before  delivery.  Field-installed 
connection pipe needs to be charged with additional refrigerant. 
(2) Confirm whether outdoor liquid and gas valves are closed. 
(3) Use vacuum pump to withdraw the air inside indoor unit and connection pipe from the 
outdoor valve, as shown below. 
 
Fig. 26 
4.4.2 Refrigerant Adding 
(1) Refrigerant quantity of outdoor unit before delivery: 
Note: 
①  The  refrigerant  amount  charged  before  delivery doesn’t  include  the  amount  that  needs  to  be  added to 
indoor units and the connection pipeline. 
②  Length  of  connection  pipe  is  decided  on  site.  Therefore  the  amount  of  additional  refrigerant  shall  be 
decided on site according to the dimension and length of field-installed liquid pipe.   
③ Record the amount of additional refrigerant for convenience of after-sales service. 
(2) Calculation of the amount of additional refrigerant 
Calculation method of the quantity of additional refrigerant (based on liquid pipe) 
Quantity of additional refrigerant = ∑length of liquid pipe X quantity of additional refrigerant 
per meter 
Quantity of additional refrigerant per meter for liquid pipe(kg/m) 
First confirm that there is no leakage from the system. When compressor is not working, 
charge additional R410a with specific amount to the unit through the filling opening of the liquid 
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