Panasonic U-72MF1U9, Technical Data Manual

Page: 59 / 118

Design of 3WAY VRF SYSTEM
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6. AIR PURGING
(3)
(4)
Do a leak test of all joints of the tubing (both indoor
and outdoor) and all service valves. Bubbles
indicate a leak. Wipe off the soap with a clean cloth
after a leak test.
After the system is found to be free of leaks, relieve
the nitrogen pressure by loosening the charge hose
connector at the nitrogen cylinder. When the system
pressure is reduced to normal, disconnect the hose
from the cylinder.
Evacuation
(1) Attach the charge hose end described in the
preceding steps to the vacuum pump to evacuate
the tubing and indoor unit. Confirm that the “Lo”
knob of the manifold valve is open. Then, run the
vacuum pump. The operation time for evacuation
varies with the tubing length and capacity of the
pump. The following table shows the amount of time
for evacuation:
Required time for evacuation
when 30 gal/h vacuum pump is used
If tubing length is
less than 49 ft.
If tubing length is
longer than 49 ft.
45 min. or more 90 min. or more
Evacuation is not necessary for the balance tube if
only 1 outdoor unit is installed.
NOTE
The required time in the above table is calculated
based on the assumption that the ideal (or target)
vacuum condition is less than –14.7 psig (–755 mmHg,
5 Torr).
Fig. 2-32
Manifold valve
Pressure
gauge
Lo Hi
Vacuum pump
Outdoor unit
Close
Open
Discharge
tube
Suction
tube
Liquid
tube
Close
Open
Balance
tube
Close
Open
Close
Open
TD831158-00̲3WAY̲VRF̲SYS.indb 45 TD831158-00̲3WAY̲VRF̲SYS.indb 45 2012/01/23 17:30:20 2012/01/23 17:30:20