Emerson Copeland Screw SCH2, Copeland Screw SCA2 Applications Manual
AE4-1322
™
Copeland ScrewCopeland Screw
Copeland Screw
Copeland ScrewCopeland Screw
™
CompressorsCompressors
Compressors
CompressorsCompressors
April 2002
Semi-Hermetic Compact Semi-Hermetic Compact
Semi-Hermetic Compact
Semi-Hermetic Compact Semi-Hermetic Compact
SCH2 & SCA2SCH2 & SCA2
SCH2 & SCA2
SCH2 & SCA2SCH2 & SCA2
High Temp Compressors
35 – 140 Horsepower
1 General1 General
1 General
1 General1 General
2 Design and functions2 Design and functions
2 Design and functions
2 Design and functions2 Design and functions
2.1 Design features
2.2 Compression process Vi control
2.3 Capacity control and start unloading
2.4 Hydraulic control
2.5 Starting the compressor
2.6 Infinite capacity control
Oil circulation
Contents
5 Economizer operation5 Economizer operation
5 Economizer operation
5 Economizer operation5 Economizer operation
Application ManualApplication Manual
Application Manual
Application ManualApplication Manual
5.1 General
5.2 Operation principal
5.3 ECO operation with subcooling circuit
5.4 ECO operation with intermediate
pressure receiver
5.5 Layout and selection
recommendations
5.6 Additional components
5.7 Control
3 Lubricants3 Lubricants
3 Lubricants
3 Lubricants3 Lubricants
4 Integration into the refrigeration circuit4 Integration into the refrigeration circuit
4 Integration into the refrigeration circuit
4 Integration into the refrigeration circuit4 Integration into the refrigeration circuit
1.1 Mounting the compressor
1.2 System layout
1.3 Guide lines for special system
variations
1.4 Additional cooling by liquid injection
1.5 Additional cooling by external oil
cooler
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
6 Electrical connections6 Electrical connections
6 Electrical connections
6 Electrical connections6 Electrical connections
6.1 Motor design
6.2 Selection of electrical components
6.3 Compressor protection system
6.4 Schematic wiring diagrams
Semi-hermetic compact screwsSemi-hermetic compact screws
Semi-hermetic compact screws
Semi-hermetic compact screwsSemi-hermetic compact screws
SCH2/SCA2 seriesSCH2/SCA2 series
SCH2/SCA2 series
SCH2/SCA2 seriesSCH2/SCA2 series
35 to 140 HP Nominal motor power35 to 140 HP Nominal motor power
35 to 140 HP Nominal motor power
35 to 140 HP Nominal motor power35 to 140 HP Nominal motor power
11
GeneralGeneral
1.
General
11
GeneralGeneral
This new series represents the result of further development to provide a simplified and favorably priced screw
compressor for use in factory made systems.
Contrary to the semi-hermetic and open type, SHM/
SHL and SDM/SDL compressor models for commercial
and industrial installation, the compact screws are
designed with an integral oil separator. The effort
involved in installation is therefore comparable with that
for semi-hermetic reciprocating compressors.
In addition to this, the electrical control and the monitoring of the oil circuit has been simplified. The proven
basic construction and the ease of service have been
retained.
The most modern screw compressor technology is now
available in the middle capacity range for compact liquid
chillers and air conditioning equipment.
2. Design and function2. Design and function
2. Design and function
2. Design and function2. Design and function
2.1 Design features
Copeland Compact screws are of the twin rotor design
with a newly-developed profile geometry (lobe ratio 5:6).
The main parts of these compressors are the two rotors
(male and female rotor), which are fitted into a closed
housing. The rotors are precisely located at both ends
in rolling contact bearings (radial and axial), which, in
conjunction with the generously sized oil supply
chambers, provides optimum emergency running
characteristics.
Owing to the specific design, this type of compressor
does not require any working valves. To protect against
reverse running when the compressor is switched off
(expansion operation) a check valve is incorporated in
the discharge chamber (this valve does not, however,
replace any check valves required by the system
design). An internal pressure relief valve is utilized for
over-pressure protection.
The compressor is driven by a three-phase asynchronous motor, which is built into the compressor housing.
The motor rotor is located on the shaft of the male
screw rotor. Cooling is achieved by cold refrigerant
AE4-1322
vapor, which mainly flows through bores in the motor
rotor.
The main technical features:
Balanced product rangeBalanced product range
Balanced product range
Balanced product rangeBalanced product range
• •
• 8 basic models
• •
• •
• Tight performance graduation
• •
Minimal space requirements and convenientMinimal space requirements and convenient
Minimal space requirements and convenient
Minimal space requirements and convenientMinimal space requirements and convenient
piping designpiping design
piping design
piping designpiping design
• Shortest installed length in its performance category
- shut-off valves / connections within compressor
dimensions
• Suction and discharge gas connections can be
rotated in 90° increments
• Terminal box accessible from top, wire access from
underneath
Universal applicationsUniversal applications
Universal applications
Universal applicationsUniversal applications
••
• R134a, R407C and R22
••
••
• R404A, R507A upon request
••
••
• With or without economizer
••
••
• Optimized R-134a version (SCA2)
••
New high-efficiency profileNew high-efficiency profile
New high-efficiency profile
New high-efficiency profileNew high-efficiency profile
• Further developed geometry
• High rigidity
• Patented manufacturing process for highest
precision
• High tip speed to minimize blow-by
Double-walled, pressure-compensated rotorDouble-walled, pressure-compensated rotor
Double-walled, pressure-compensated rotor
Double-walled, pressure-compensated rotorDouble-walled, pressure-compensated rotor
housinghousing
housing
housinghousing
••
• Extremely stable, therefore no expansion even at
••
high pressure levels
••
• Additional sound attenuation
••
Proven, long-life bearings with pressure unloadingProven, long-life bearings with pressure unloading
Proven, long-life bearings with pressure unloading
Proven, long-life bearings with pressure unloadingProven, long-life bearings with pressure unloading
• Robust axial bearings in tandem configuration
• Bearing chamber pressure isolated by seal rings
• Pressure unloading of axial bearings
Optimized oil managementOptimized oil management
Optimized oil management
Optimized oil managementOptimized oil management
• Three-stage oil separator
• Long-life oil filter 10 µ mesh size
• Pressure relieved bearing chamber ensuring minimum refrigerant dilution in the oil and thus higher
viscosity
Large volume motor for part winding or direct startLarge volume motor for part winding or direct start
Large volume motor for part winding or direct start
Large volume motor for part winding or direct startLarge volume motor for part winding or direct start
- optional star delta design- optional star delta design
- optional star delta design
- optional star delta design- optional star delta design
• Especially high efficiency
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
2
• Integrated PTC sensors in each winding coil
• Slot keys for maximum operating safety
• Stator is slide fit (field replaceable)
Intelligent electronicsIntelligent electronics
Intelligent electronics
Intelligent electronicsIntelligent electronics
• Thermal motor temperature control by winding PTCs
• Phase sequence control for direction of rotation
• Manual reset lock-out
• Oil temperature protection by PTC sensor
Flexible with additional coolingFlexible with additional cooling
Flexible with additional cooling
Flexible with additional coolingFlexible with additional cooling
• Direct liquid injection
• External oil cooler for extended application and
highest efficiency
Dual capacity controlDual capacity control
Dual capacity control
Dual capacity controlDual capacity control
• Infinite or 4-step slide control with V
compensation.
i
Alternative operation modes by varying the control
sequence only - no need for compressor modification
• Simple control by solenoid coils
• Automatic start unloading
Economizer with sliding suction positionEconomizer with sliding suction position
Economizer with sliding suction position
Economizer with sliding suction positionEconomizer with sliding suction position
• Unique for compact screws
• Efficient economizer operation with part load as well
• Highest cooling capacity and energy efficiency at full
and part load conditions
Fully equippedFully equipped
Fully equipped
Fully equippedFully equipped
• Capacity control / start unloading
• Suction and Discharge shut-off valve
• Check valve in discharge gas outlet
• Oil sight glass
• Insertion type oil heater with sleeve
• Oil fill / drain service valve
• Suction gas filter with large surface are and fine mesh
• Electronic protection system
Proven optional accessoriesProven optional accessories
Proven optional accessories
Proven optional accessoriesProven optional accessories
• Oil level switch
• Shut-off valve / adapter for economizer operation and
liquid injection
• Adapter for external oil cooler
2.2 Compression process V2.2 Compression process V
2.2 Compression process V
2.2 Compression process V2.2 Compression process V
-control-control
-control
-control-control
ii
i
ii
With screw compressors, suction, compression and
discharge occur in one flow direction. With this process
the suction gas is pressed into the profile hollows by the
profile peaks. The volume is steadily reduced and it is
thereby compressed. The compressed gas is then
discharged through a discharge port whose size and
geometry determine the so called “internal volume ratio
AE4-1322
(Vi)”. This value must have a defined relationship to the
mass flow and the working pressure ratio, to avoid
losses in efficiency due to over- and under-compression.
The internal discharge ports of the SCH2/SCA2 screw
compressors are designed for a very wide application
range.
In view of high efficiency and operational safety a part of
the discharge channel is integrated into the control
slide, which enables a Vi control at part load conditions.
Due to this the internal volume ratio (Vi) virtually remains constant down to approximately 70% part load.
The economizer channel built into the control slide is
another outstanding feature (figure 3). It enables a fully
functional operation of the subcooler circuit independently from the compressor’s load conditions. This is a
design solution which is unique for screw compressors
of this size. This ensures highest possible capacity and
efficiency at both full and part load conditions. For
details regarding economizer operation see Section 5.
2.3 Capacity control and start unloading2.3 Capacity control and start unloading
2.3 Capacity control and start unloading
2.3 Capacity control and start unloading2.3 Capacity control and start unloading
SCH2/SCA2 models are provided as a standard with a
“Dual Capacity Control” (slide system). This allows for
infinite infinite
infinite or
infinite infinite
4-step capacity control4-step capacity control
4-step capacity control without compressor
4-step capacity control4-step capacity control
modifications. The different operating modes can be
achieved by changing the control sequences of the
solenoid valves.
The special geometry of the slide means that the
volume ratio Vi is adjusted to the operating conditions in
part-load operation. This provides particularly high
efficiency.
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
3
AE4-1322
Oil Hydraulic Scheme
Another feature of this system is the automatic startunloading. It reduces starting torque and acceleration
times considerably. This not only puts lower stresses
on motor and mechanical parts but also reduces the
load on the power supply network.
Significant design features are the robust dimensioning
as well as the precise guidance of the slide elements
and the control piston. Capacity control is achieved by
means of solenoid valves that are flanged on to the
compressor. A “dual set point controller” or any similar
component is suitable as a control module.
2.4 Hydraulic control2.4 Hydraulic control
2.4 Hydraulic control
2.4 Hydraulic control2.4 Hydraulic control
Figure 3 shows the design principle of the hydraulic
scheme. By moving the slide the suction gas flow is
controlled.
If the slide is moved totally to the suction slide (in the
figure 3 to the left), the working space between the
profiles is filled with suction gas. The more the slide is
moved to the discharge slide, the smaller the resulting
profile volume becomes. Less refrigerant is taken in.
The mass flow is lower, and the cooling capacity
decreases.
Figure 3
chamber increases. The slide is moved to the suction
side. The cooling capacity increases.
If the valve CR1, CR2 or CR3 is opened, the pressure
on the hydraulic piston decreases. By means of the
discharge gas the slide is pressed to the discharge
side. The cooling capacity is reduced.
2.5 Starting the compressor2.5 Starting the compressor
2.5 Starting the compressor
2.5 Starting the compressor2.5 Starting the compressor
During the shut - down of the compressor the solenoid
valve CR3 is open. The pressure in the hydraulic
cylinder is then released. The spring (fig. 3) pushes the
slide to the discharge side end position.
When starting the compressor, it is unloaded. Valve
CR4 is energized on demand thus moving the slide
towards the suction side. The refrigerating capacity
increases to the set load condition by energizing the
valves CR1, CR2 or CR3.
2.6 Infinite capacity control2.6 Infinite capacity control
2.6 Infinite capacity control
2.6 Infinite capacity control2.6 Infinite capacity control
Infinite capacity control is recommended for systems
where high control accuracy is required. For control
principle see charts A, B, and C.
The slide is controlled by a hydraulic piston. If the valve
CR4 is opened, the oil pressure in the pressure
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
If the actual value is within the set control range H, the
cooling demand of the plant remains unchanged. Then
4
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there is no need to move the slide. No solenoid valve
is energized.
The control input can be the air or water temperature at
the evaporator or the suction pressure.
Chart A
Control Sequence – Infinite Capacity ControlControl Sequence – Infinite Capacity Control
Control Sequence – Infinite Capacity Control
Control Sequence – Infinite Capacity ControlControl Sequence – Infinite Capacity Control
Minimum CapacityMinimum Capacity
Minimum Capacity
Minimum CapacityMinimum Capacity
mm
m
mm
CR 1 2 3 4
Start/Stop mmlm
⇑⇑
Cap
⇑ mmml
⇑⇑
⇓⇓
Cap
⇓ mmlm
⇓⇓
⇔⇔
Cap
⇔ mmmm
⇔⇔
Cap. 100% mmml
Cap. Min.W mmlm
Chart B
Control Sequence – Infinite Capacity ControlControl Sequence – Infinite Capacity Control
Control Sequence – Infinite Capacity Control
Control Sequence – Infinite Capacity ControlControl Sequence – Infinite Capacity Control
Minimum Capacity 50%Minimum Capacity 50%
Minimum Capacity 50%
Minimum Capacity 50%Minimum Capacity 50%
Cap
4 Cap.
⇑⇑
⇑
⇑⇑
mm
m
mm
mm
m
mm
mm
m
mm
ll
l
ll
ll
l
ll
mm
m
mm
mm
m
mm
Min.50%
Increased cooling demandIncreased cooling demand
Increased cooling demand
Increased cooling demandIncreased cooling demand
If the actual value exceeds the upper set point, the
cooling demand has increased (operating point A in fig.
4). The solenoid valve CR4 is opened for short intervals
till the actual value is within the set control range again
(operating point B). Now the compressor operates with
increased cooling capacity.
Chart C
Control Sequence – 4-Step Capacity ControlControl Sequence – 4-Step Capacity Control
Control Sequence – 4-Step Capacity Control
Control Sequence – 4-Step Capacity ControlControl Sequence – 4-Step Capacity Control
Decreased cooling demandDecreased cooling demand
Decreased cooling demand
Decreased cooling demandDecreased cooling demand
A decreased cooling demand falls below the lower set
point (operating point C). The solenoid valve CR3 now
opens for short intervals till the actual value is within
the set control range again (operating point D). The
compressor operates with decreased cooling capacity.
With the solenoid valves CR3 / CR4, capacity can be
controlled between 100% and nominally 25%. Alternatively valves CR2 / CR4 can be energized; in this case
control will be limited between 100% and nominally
50%.
The limitation to a minimum of approximately 50%
cooling capacity is recommended for the following
application conditions (control with valves CR2 / CR4):
• In case of operation at high-compression ratios /
condensing temperatures, the main concern is high
discharge temperature.
• For systems with multiple compressors either used
in split or singlecircuits. Under these conditions
capacity control between 100 and 50%, in combination with individual compressor on/off cycling,
guarantees highest possible efficiency – without
significant restrictions in the application range. Due
to the usually lowered condensing temperature at
part load conditions, the lead compressor can even
be operated very effectively down to nominal 25% of
cooling capacity (with valves CR3 / CR4)
2.7 4-step capacity control2.7 4-step capacity control
2.7 4-step capacity control
2.7 4-step capacity control2.7 4-step capacity control
This type of capacity control is particularly suited to
systems with high inertia – in connection with indirect
cooling, for example. Liquid chillers are typical applications. Chart C shows the control of the solenoid valves
or the individual capacity steps.
CR 1 2 3 4
Start/Stop mmlm
Cap 25% mmly
Cap 50% mlmy
Cap 75% lmmy
Cap. 100% mmmm
Solenoid Coil De-Energized Solenoid Coil De-Energized
m
Solenoid Coil De-Energized
Solenoid Coil De-Energized Solenoid Coil De-Energized
Solenoid Coil EnergizedSolenoid Coil Energized
l
Solenoid Coil Energized
Solenoid Coil EnergizedSolenoid Coil Energized
Solenoid Coil Pulsing (10 secs. on / 10 secs. off) Solenoid Coil Pulsing (10 secs. on / 10 secs. off)
y
Solenoid Coil Pulsing (10 secs. on / 10 secs. off)
Solenoid Coil Pulsing (10 secs. on / 10 secs. off) Solenoid Coil Pulsing (10 secs. on / 10 secs. off)
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
The cycle time of the intermitting valve, CR4, should be
adjusted to about 10 seconds before commissioning.
Even shorter intervals may be necessary, particularly
with systems with high pressure differences. Therefore,
in this case adjustable time relays should be used.
For this type of operation a restriction of minimum
refrigeration capacity to approximately 50% is also
recommended, as with the systems described in
Section 2.6. Control is then effected with the CR4 valve
(intermittent) and with CR1 (75%) and CR2 (50%).
5
AE4-1322
2.8 Oil circulation2.8 Oil circulation
2.8 Oil circulation
2.8 Oil circulation2.8 Oil circulation
The lubrication circuit is designed as is typical for
screw compressors. This type of design, however, has
a vessel directly flanged-on to the compressor housing
at the high-pressure side. It contains the oil reservoir.
The vessel simultaneously serves as an oil separator.
The oil circulation results from the pressure difference
to the oil injection point, where the pressure level is
slightly above suction pressure. The oil flows through a
generously sized filter element to the throttle point and
subsequently to the bearing chambers and the profile
spaces of the rotors. The oil is then transported
together with the refrigerant vapor in the direction of
compression. In addition to lubrication it also provides
a dynamic seal between the rotors and between the
housing and the rotors. The oil then flows together with
the compressed vapor into the reservoir vessel. Here oil
and vapor are separated in a highly efficient process.
The oil collects in the lower part of the separator vessel
Figure 4
Infinite capcity control scheme
and flows back into the compressor either direct or via
an external oil cooler. Depending on the operating
conditions the circulating oil must be cooled with liquid
injection or an external oil cooler (see Section 4.4 and
4.5)
Monitor the oil circuitMonitor the oil circuit
Monitor the oil circuit
Monitor the oil circuitMonitor the oil circuit
• For short circuits
additional cooling and for small system volumes
and refrigerant charges: indirect monitoring by
means of oil temperature protection (standard)
without without
without refrigerant injection for
without without
CAUTION!CAUTION!
CAUTION!
CAUTION!CAUTION!
Lack of oil leads to a dramaticLack of oil leads to a dramatic
Lack of oil leads to a dramatic
Lack of oil leads to a dramaticLack of oil leads to a dramatic
temperature increase.temperature increase.
temperature increase.
temperature increase.temperature increase.
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
6
AE4-1322
• For circuits
cooling and / or for greater system volumes:
Direct monitoring by means of an oil level monitor in
the oil separator(optional accessory) is recommended.
3 Lubricants3 Lubricants
3 Lubricants
3 Lubricants3 Lubricants
Apart from the lubrication it is also the task of the oil to
provide dynamic sealing of the rotors. Special demands
result from this with regard to viscosity, solubility and
foaming characteristics. Copeland approved oils may
therefore be used only.
Important instructionsImportant instructions
Important instructions
Important instructionsImportant instructions
• Observe the application limits of the compressors.
• The lower limit value of the discharge gas temperature (140°F) is a reference value only. It must be
ensured by sufficient suction super-heat that the
discharge gas temperature is at least 54°F (R134a,
R404A / R507A mi. 36°F) above the condensing
temperature.
• Ester oils Solest170 (for HFC refrigerants) and
CP4214-320 (for R22) are very hygroscopic. Special
care is therefore required when dehydrating the
system and when handling open oil containers.
withwith
with refrigerant injection for additional
withwith
Figure 5
Mounting and installation
4.1 Mounting the compresso4.1 Mounting the compresso
4.1 Mounting the compressor
4.1 Mounting the compresso4.1 Mounting the compresso
With stationary systems the compressor has to be
installed horizontally.
In case of marine application, mounting in direction of
the longitudinal axis of the boat may be required.
Detailed layout recommendation can be provided upon
request.
Anti-vibration mountingsAnti-vibration mountings
Anti-vibration mountings
Anti-vibration mountingsAnti-vibration mountings
• A corrected design may be necessary for directexpansion evaporators with finned tubes on the
refrigerant side (consultation with manufacturer).
The above information corresponds to the present
status of our knowledge and is intended as a guide for
general applications. This information does not have
the purpose of confirming certain oil characteristics or
their suitability for a particular case.
4 Integration into the refrigeration circuit4 Integration into the refrigeration circuit
4 Integration into the refrigeration circuit
4 Integration into the refrigeration circuit4 Integration into the refrigeration circuit
Compact screw compressors are well suited for
integration in factory-assembled plants (liquid chillers
and air conditioning units). Their use in extended
systems is also possible, for example, with remotely
installed condenser.
Systems with multiple compressors should preferably
be designed with individual circuits. Parallel compound
is possible, but requires a special oil equalizing
system by means of oil level control.
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
Rigid mounting of the compressor is possible. The use
of anti-vibration mountings especially matched to the
compressors is recommended, however, to reduce the
transmission of body radiated noise.
With direct mounting on water cooled condensers:
CAUTION!CAUTION!
CAUTION!
CAUTION!CAUTION!
Do not mount the compressor directlyDo not mount the compressor directly
Do not mount the compressor directly
Do not mount the compressor directlyDo not mount the compressor directly
on the condenseron the condenser
on the condenser
on the condenseron the condenser
condenser structural mmember! condenser structural mmember!
condenser structural mmember!
condenser structural mmember! condenser structural mmember!
Damage of the condenser is possibleDamage of the condenser is possible
Damage of the condenser is possible
Damage of the condenser is possibleDamage of the condenser is possible
(fatigue fractures). Use anti-vibration (fatigue fractures). Use anti-vibration
(fatigue fractures). Use anti-vibration
(fatigue fractures). Use anti-vibration (fatigue fractures). Use anti-vibration
mountings!mountings!
mountings!
mountings!mountings!
The installation of the anti-vibration mountings is shown
in figure 5. The bolts should only be tightened until
slight deformation of the upper rubber disc is just
visible.
7
. Do not use the. Do not use the
. Do not use the
. Do not use the. Do not use the
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