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below the center of the compressor sight-glass. The oil
level should be checked with the compressor "off" to
avoid the sump turbulence when the compressor is
running. Cycling the compressor for a shorter period
than this, for instance to maintain very tight temperature
control, will result in progressive loss of oil and damage
to the compressor.
Long Pipe Lengths / High Refrigerant Charge
Some systems may contain higher than normal
refrigerant charges. Systems with large reheat coils,
low ambient condenser flooding, or systems with
multiple heat exchangers are among some system
configurations that may require additional lubricant.
If the compressors have a sight glass for oil level
viewing, the oil level should always be checked during
OEM
assembly,
field
servicing. An estimation of the amount of additional
lubricant to add to the compressor(s) when the circuit
charge exceeds 20 pounds of refrigerant is as follows:
Single compressor application: 0.5 fluid ounce of oil per
pound of refrigerant.
For multiple compressor applications, refer to AE4-1430
for additional oil estimate for tandems and trios.
The oil level must be carefully monitored during system
development, and corrective action should be taken if
the compressor oil level falls below the minimum oil
level. The compressor oil level should be checked with
the compressor "off" to avoid the sump turbulence when
the compressor is running.
These compressors are available to the OEM with a
production sight-glass that can be used to determine the
oil level in the compressor in the end-use application.
These compressors are also available to the OEM with
an oil Schrader fitting on the side of the compressor to
add additional oil if needed because of long lengths of
piping or high refrigerant charge. No attempt should be
made to increase the oil level in the sight-glass above
the 3/4 full level. A high oil level is not sustainable in the
compressor and the extra oil will be pumped out into the
system causing a reduction in system efficiency and a
higher-than-normal oil circulation rate.
Suction and Discharge Fittings
The compressors have copper plated steel suction and
discharge or threaded rotalock fittings. See Figure 2 for
assembly line and field brazing recommendations and
Table 1 for rotalock torque requirements.
© 2020 Emerson Climate Technologies, Inc.
commissioning,
and
field
System Tubing Stress
System tubing should be designed to keep tubing
stresses under the endurance limit of the copper tubing
type used (i.e., Type K, L, etc.). Start, stop and running
(resonance) cases should be evaluated to ensure long
term reliability.
For variable speed applications, the suction and
discharge tubing must be evaluated to determine the
resonant frequencies. Once the resonant frequencies
are known, they can be shifted to a desired range by
changing the mass of the line for constant speed
applications or they can be avoided for variable speed
applications. Application engineering is available to
recommend additional tests and to evaluate test results.
Accumulators
The use of accumulators is very dependent on the
application. The Copeland scroll compressor's inherent
ability to handle liquid refrigerant during occasional
operating flood back situations make the use of an
accumulator unnecessary in most applications. The
OEM is responsible for determining if an accumulator is
needed and the selection of the accumulator.
Consideration for additional oil needed for the
accumulator should be taken.
Off-Cycle Migration Control
Excessive migration of refrigerant to the compressor
during the off-cycle can result in oil pump-out on start
up, excessive starting noise and vibration, bearing
erosion, and broken scrolls if the hydraulic slugging
pressure is high enough. For these reasons, off-cycle
refrigerant migration must be minimized. The following
three
sections
summarize
techniques.
Crankcase Heaters
A crankcase heater is required when the system charge
exceeds the values listed in Table 2. This requirement
is independent of system type and configuration. The
initial start-up in the field is a very critical period for any
compressor because all load-bearing surfaces are new
and require a short break-in period to carry high loads
under adverse conditions. The crankcase heater must
be turned on a minimum of 12 hours prior to starting the
compressor. This will help prevent oil dilution and
bearing stress on initial startup.
To properly install the crankcase heater, the heater
should be installed in the location illustrated in Figure 4.
Tighten the clamp screw carefully, ensuring that the
7
AE4-1486 R1
off-cycle
migration
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