Thermo King T-1000R Series Maintenance Manual page 119

Refrigeration Service Procedures
NOTE: The presence of refrigerant in the
compressor oil may prevent a low micron
reading from being achieved. The oil can
continue to "outgas" for long periods of
time. If the micron level appears to stall after
1/2 hour or 45 minutes between 1000 and
1500 microns, back seat the suction service
valve and observe the micron gauge. A sharp
drop in the micron reading (300 to 500
microns) would indicate that refrigerant is
present in the oil or a leak exists in the
compressor area. The micron gauge reads
"ATM" if there is a leak to the atmosphere.
See Figure 203 "Pressure Rise Graphs"
below.
Isolate the pump from the system by closing the
proper valve. Watch the movement of the vacuum
gauge needle. If the needle continues to rise,
this is an indication that a leak exists in the unit
or the connecting line. The leak must then be
located and eliminated.
118
Leak
Figure 203: Pressure Rise Graphs
7. When the desired micron level has been
achieved (500 to 1000 microns), close valve
V-1, stop the pump.
8. Observe the reading on the micron gauge after
5 minutes have elapsed. The vacuum rise
should not exceed 2000 microns.
• If the vacuum level exceeds 2000 microns
after 5 minutes, a leak is present or
additional evacuation time is required.
(See the Figure 203 "Pressure Rise
Graphs" below.)
• If the vacuum level is acceptable, proceed
to unit charging.
Moisture
Should the needle show a pressure rise but
finally level off to practically a constant mark,
this is an indication that the system is vacuum
tight but is still too wet, requiring additional
dehydration and pumping time.