Modern Refrigeration and Air Conditioning
ix
172 Modern Refrigeration and Air Conditioning
Caution
Liquid Recovery Capability
Not all recovery machines are designed for liquid
recovery. Attempting to recover liquid into a recovery
machine without this capability could seriously damage
the recovery machine’s compressor. A recovery machine
that can recover liquid refrigerant has a restriction that
operates like a metering device by fl ashing liquid refriger-
ant into vapor before it is pumped through the recovery
machine’s compressor. Before attempting this procedure,
always refer to the recovery machine’s operating manual
to determine if it is capable of liquid recovery.
Liquid Refrigerant Recovery Procedure
For this procedure, refer to Figure 8-5 and
your recovery machine’s operating manual.
1. Turn off power to the refrigeration system.
2. Connect the system as shown in Figure 8-5.
3. To prevent overfi lling, connect the recovery
unit’s 80% overfi ll cord to the recovery cylinder,
if it is equipped with a properly operating level
switch safety device.
4. Set up a digital charging scale to monitor the
recovery cylinder’s weight. Remember to fi nd
Liquid Recover y Capabilit y
Not all recovery machines are designed for liquid
recovery. Attempting to recover liquid into a recovery
machine without this capability could seriously damage
the recovery machine’s compressor. A recovery machine
that can recover liquid refrigerant has a restriction that
operates like a metering device by fl ashing liquid refriger-
ant into vapor before it is pumped through the recovery
machine’s compressor. Before attempting this procedure,
always refer to the recovery machine’s operating manual
to determine if it is capable of liquid recovery.
Liqu u u u
y yo o o u u ur
1 1 . .
2 2 . .
3 3 . .
4 4 . .
the cylinder tare weight, and calculate the
total maximum weight the recovery cylinder
and refrigerant can weigh.
5. Position the recovery machine’s control valves
for direct liquid recovery after referring to the
operator’s manual for specific instructions.
6. Switch on the recovery machine.
7. Watch the sight glass and pressure gauges
on the gauge manifold and on the recovery
machine. Monitor how cold the fi lter-drier,
hose, and hose connectors are between the
gauge manifold and recovery machine inlet
by feeling them. The recovery machine has
begun pumping vapor refrigerant when the
pressure on the high-pressure gauge of the
manifold has dropped, and the hose connec-
tors and gauge manifold no longer feel as cold
as previously.
8. Fully open the low-side valve on the gauge
manifold, allowing vapor refrigerant to be
recovered from the low side of the refrigera-
tion system. This step marks the switch from
liquid recovery to vapor recovery. Complete
the rest of the recovery procedure as if it were
the vapor recovery method.
HVAC system
High-side
service valve
(mid-position)
Liquid line
Low-side
service valve
(mid-position)
Low-side
valve closed
High-side
valve open
In-line
filter-drier
Sight
glass
Recovery
machine
Outlet Inlet
Recovery
cylinder
Vapor valve Scale
Suction line
Goodheart-Willcox Publisher
Figure 8-5. The liquid recovery method draws as much liquid refrigerant as possible from the high side of the system before
valve positions must be changed to complete the process using the vapor recovery method.
5 5 . .
6 6 . .
7 7 7 . .
b
b
8 8 . .
Fi gure 8-5. The liquid
valve positions must be
Cautions alert students of
practices that could potentially
damage equipment or instruments.
Step-by-Step Procedures
are highlighted throughout
the textbook to provide clear
instructions for hands-on service
activities. Students can refer to
these procedures easily.
Safety Notes alert students of
potentially dangerous materials
and practices.