Daikin VRV REYQ96MTJU Design, Installation & Testing Instruction page 41

Si39-406
The evacuation of air conditioner piping provides the following effects.
1. Vacuum drying
2. Removes air and nitrogen (used in air-tightness test) from the inside of pipes.
Therefore, it is necessary to ensure that the both purposes have been achieved in the vacuum
drying operation.
Choosing a General
Refrigerant piping content volume of the VRVII R410A Series is larger than the VRV Inverter
Vacuum Pump
Series, and consequently takes more time for vacuum drying. If you have time to spare, you may
use the same vacuum pump, but if you want to save time, you will have to use a pump with higher
exhaust velocity (exhaust volume).
The Necessity for Counter Flow Prevention
After the vacuum process of the refrigerant cycle, the inside of the hose will be vacuumed after
stopping the vacuum pump, and the vacuum pump oil may flow back. Moreover, if the vacuum
pump stops during the operation by some reason, the same thing happens.
In such cases, different oil mixes in the HFC system refrigerant apparatus cycle, and becomes the
cause of a refrigerant circuit trouble. Therefore, in order to prevent the counter flow from the
vacuum pump, a check valve is needed.
Vacuum pump with check valve or vacuum pump adapter
General Information
Key points
Lower the degree of vacuum to below –14.6psi (–755mmHg)
Vacuum pump with
check valve
(V1216)
Vacuum pump adapter
Reverse flow preventive
vacuum adapter
Installation
35