Compressor Removal And Replacement; Copeland Scroll Compressor; Features; Troubleshooting - Carrier R-22 Application Manual And Service Manual

acids, contaminate system. If burnout is severe enough, system
must be cleaned before replacement compressor is installed. The 2
types of motor burnout are classified as mild or severe.
In mild burnout, there is little or no detectable odor. Compressor
oil is clear or slightly discolored. An acid test of compressor oil
will be negative. This type of failure is treated the same as
mechanical failure. Liquid-line strainer should be removed and
liquid-line filter drier installed.
In a severe burnout, there is a strong, pungent, rotten-egg odor.
Compressor oil is very dark. Evidence of burning may be present
in tubing connected to compressor. An acid test of compressor oil
will be positive. Complete system must be reverse flushed with
refrigerant. AccuRater™ or TXV must be cleaned or replaced. In
a heat pump, accumulator and reversing valve are replaced. These
components are also removed and bypassed during reverse-
flushing procedure. Remove and discard liquid-line strainer. After
system is reassembled, install liquid-line and suction-line filter
driers. Run system for 2 hrs. Discard both driers and install new
liquid-line drier only.
Step 4—Compressor Removal And Replacement
Once it is determined that compressor has failed and the reason
established, compressor must be replaced.
Wear safety glasses and gloves when handling refrigerants
and when using brazing torch.
1. Shut off all power to unit.
2. Remove and recover all refrigerant from system until pressure
gages read zero psi. Use all service ports.
3. Disconnect electrical leads from compressor. Disconnect or
remove crankcase heater and remove compressor-holddown
bolts.
4. Cut compressor from system with tubing cutters. Do not use
brazing torch for compressor removal. Oil vapor may ignite
when compressor is disconnected.
5. Scratch matching marks on stubs in old compressor. Make
corresponding marks on replacement compressor.
6. Use torch to remove stubs from old compressor and to reinstall
them in replacement compressor.
7. Use copper couplings to tie compressor back into system.
8. Evacuate system, recharge, and check for normal system
operation.
9. Copeland CR-6 and scroll compressors have copper-plated,
steel-suction ports. Excess heat during brazing will burn off
copper plating. See Brazing section for additional information.

COPELAND SCROLL COMPRESSOR

Step 1—Features
The scroll compressor pumps refrigerant through the system by the
interaction of a stationary and an orbiting scroll. (See Fig. 29.) The
scroll compressor has no dynamic suction or discharge valves, and
it is more tolerant of stresses caused by debris, liquid slugging, and
flooded starts. Due to the design of the scroll compressor, the
internal compression components unload (equalize pressure) on
shutdown. The white oil (Sontex 200LT) used in the scroll is
compatible with 3GS oil, which can be used if additional oil is
required. (See Table 14 for oil recharge requirements.)
Step 2—Troubleshooting
Troubleshooting mechanical or electrical problems in a scroll
compressor is the same as for a reciprocating compressor, except
that a scroll compressor should never be allowed to pump into a
Scroll Gas Flow
Compression in the scroll is
created by the interaction of
an orbiting spiral and a
stationary spiral. Gas enters
an outer opening as one of the
spirals orbits.
2
The open passage is sealed off
as gas is drawn into the spiral.
4
By the time the gas arrives at
the center port, discharge
pressure has been reached.
Fig. 29—Scroll Compressor Refrigerant Flow
vacuum. If a pumpdown procedure is used, the scroll compressor
is capable of pumping into a vacuum very quickly, which could
cause fusite arcing and compressor failure. See Step 4 of Recip-
rocating Compressor section for removal and replacement.
Step 3—Discharge Thermostat
Some scroll compressors have a discharge thermostat that recip-
rocating compressors do not have. This thermostat is mounted in a
well in the top of the compressor shell to sense if the discharge
temperature reaches 290°F and shuts down the compressor to
prevent damage to it. When the temperature of the thermostat
reaches 140°F, power is restored to the compressor.
To determine if the thermostat is operating properly, either attach
the thermocouple of an electronic thermometer to the dome of the
compressor near the thermostat, or remove the thermostat and
place the thermocouple inside the well. The electronic thermom-
eter must be capable of reading at least 300°F. Start the unit and let
it run for at least 15 minutes to obtain normal operating conditions.
Watch the thermometer to see if it is approaching 270°F. If the
thermocouple is located on the dome near the discharge thermo-
stat, there could be a 20° difference between well and dome
temperatures. If the temperature approaches 270°F, repair system
problem, such as low charge, blocked condenser coil, and so forth.
If the temperature does not approach 270°F, replace discharge
thermostat.
Replacing Discharge Thermostat
To replace the discharge thermostat, refer to the Installation
Instructions packaged with the replacement discharge-thermostat
kit. (See Fig. 30.)
28
1
3
As the spiral continues to orbit,
the gas is compressed into an
increasingly smaller pocket.
5
Actually, during operation, all
six gas passages are in various
stages of compression at all
times, resulting in nearly con-
tinuous suction and discharge.
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