Daikin R22, Руководство по проектированию трубопроводов для хладагента, Страница: 21 / 78

www.DaikinApplied.com 21 AG 31-011 • REFRIGERANT PIPING DESIGN
Oil Return in Suction and Discharge Risers
Table 10 on page 45 through Table 18 on page 49 show
minimum capacity oil return for suction and discharge risers.
When unloading capability exists, risers should be checked
to verify that the minimum capacity allows for acceptable oil
return. For air conditioning applications that contain less than
100 feet (30.5 m) of piping and no more than 33% capacity
reduction per circuit, a properly sized riser should be found.
It may be necessary to use a smaller pipe diameter for the
riser, which creates a higher than desired pressure drop at full
capacity, for optimal oil movement. To compensate, a larger
diameter pipe may be used for horizontal runs to minimize the
total pressure drop.
Figure 13 shows the traditional method for reducing the pipe
diameter for suction and discharge risers. This approach will
prevent oil from being trapped in the horizontal portion of the
pipe.
Figure 14 shows a preferred method for RCS Condensing
Units. It replaces 90° elbows at “X” and “Y” with 45° elbows to
minimize the oil collection in the trap and replaces the vertical
reducer “Z” with an eccentric horizontal reducer.
Figure 13: Traditional Reduction Fittings for Risers
Figure 14: Preferred Reduction Fittings for Risers
Install expander
in horizontal pipe
Install reducer
in vertical pipe
X
Z
Y
Install expander
in horizontal pipe
Install reducer
in horizontal pipe
X Z
Y
45°