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pressure oil management systems. The differential
pressure required for sufficient oil flow from the oil
reservoir to the compressor crankcase depends upon
the system. However, 20 PSIG (1.4 Bar) can be used as
a minimum pressure differential value. Refer to Figure
3 and Table 4
Accumulators
Irrespective of system charge, oil dilution may occur if
large amounts of liquid refrigerant repeatedly flood back
to the compressor during normal running cycles, defrost,
and varying loads.
If adequate Compressor Superheat cannot consistently
be maintained at minimum of 36°F (20°C) an
accumulator may be required, as well as the addition of
liquid to suction heat exchanger or other means as
assuring 36°F (20°C) Superheat.
Screens
The use of screens finer than 30 x 30 mesh (0.6 mm
openings) anywhere in the system should be avoided
with these compressors. Field experience has shown
that finer mesh screens used to protect expansion
valves, capillary tubes, or accumulators can become
temporarily or permanently plugged with normal system
debris and block the flow of either oil or refrigerant to the
compressor. Such blockage can result in compressor
failure.
Mufflers
External
mufflers,
normally
compressors in the past, may not be required for
Copeland Scroll compressors.
Individual system tests should be performed to verify
acceptability of sound performance. If adequate
attenuation is not achieved, use a muffler with a larger
cross-sectional area to inlet area ratio. A ratio of 20:1 to
30:1 is recommended.
A hollow shell muffler will work quite well. Locate the
muffler 6-18 inches from the compressor for the most
effective operation. The farther the muffler is placed
from the compressor within these ranges, the more
effective. Choose a muffler with a length of 2-6 inches.
Electrical Connection
The compressor terminal box has a wiring diagram on
the inside of its cover. Before connecting the
compressor, ensure the supply voltage, the phases and
© 2017 Emerson Climate Technologies, Inc.
applied
to
piston
6
the frequency match the nameplate data. Refer to
Figure 5 for details.
The terminal box is IP21 for all models from ZO21K* to
ZO104K*. The ZO Scroll compressors have three-
phase induction motors connected in star. Copeland
Scroll compressors, like several other types of
compressors, will only compress in one rotational
direction. Three phase compressors will rotate in either
direction depending upon phasing of the power. Since
there is a 50% chance of connecting power in such a
way as to cause rotation in the reverse direction, it is
important to include notices and instructions in
appropriate locations on the equipment to ensure that
proper rotation direction is achieved when the system is
installed and operated. Verification of proper rotation
direction is made by observing that suction pressure
drops and discharge pressure rises when the
compressor is energized. Reverse rotation will result in
no pressure differential as compared to normal values.
A compressor running in reverse will sometimes make
an abnormal sound. There is no negative impact on
durability caused by operating three-phase Copeland
Scroll compressors in the reversed direction for a short
period of time (under one hour). After several minutes of
reverse operation, the compressor's internal overload
protector will trip shutting off the compressor. If allowed
to repeatedly restart and run in reverse without
correcting the situation, the compressor bearings will be
permanently damaged because of oil loss to the system.
All three phase scroll compressors are wired identically
internally. As a result, once the correct phasing is
determined for a specific system or installation, connecting
properly phased power leads to the identified compressor
electrical (Fusite™) terminals will maintain the proper
rotational direction (see Figure 7). All three phase scrolls
will continue to run in reverse until the internal overload
protector opens or the phasing is corrected.
Crankcase Heaters
A crankcase heater is always required. The crankcase
heater must be turned on a minimum of 12 hours prior
to starting the compressor and must remain energized
during the compressor off cycle.
See Table 3 for reference.
Motor Protection
For the ZO range of compressors, conventional inherent
internal line break motor protection is provided.
AE4-1372 R4
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