Daikin VRV REYQ96MTJU Design, Installation & Testing Instruction page 133

Si39-406
7.10.5 Example 5:
Situation The noise of the refrigerant flow during defrosting is excessive.
Source of The angle of the fittings was incorrect and needed to be rectified as shown in the following figure.
Problem and
1.
Remedial Action
2.
Main Points
General Information
Excessive noise due to incorrect angling of REFNET joints
REFNET joints
The REFNET joints should be installed such that branches meet the main pipe either
horizontally or vertically at an angle of exactly 90 degrees.
REFNET header
The REFNET header is a lateral flow pipe and should be fitted so as to allow horizontal branch
fittings. (Vertical or sloping fitting is not permissible.)
Reasons for using refrigerant branch kit
Fittings of REFNET joints or headers which are not carried out in strict accordance with the
principles outlined here may result in complaints relating, for example, to "poor performance" of
the system or "noisy refrigerant flow". (To prevent unbalance flow or oil shortage)
Appendix
127