Emerson Copeland 4MF-13X - Capacity Control and Application Range

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Appendix 4: Stream Semi-Hermetic Compressor Capacity control
Compressors in the higher capacity range need some form of capacity control to accommodate varying refrigeration load.
The capacity control kit supplied by Emerson Climate Technologies will reduce the refrigeration capacity along with a
similar proportional reduction in power Input. This ensures optimum performance even in part load.
Capacity control is also required when the condensing pressure falls with a drop in ambient air temperature. The
compressor suction condition, refrigerant volume and mass ow rate will remain unchanged. The capacity will increase due
to the increase in Δh, along with the increase in volumetric efciency (see the pH chart below).
Same compressor inlet condition
kJ/kg
h
Δh
Pressure
P
Compressor capacity
design condition
Additional capacity at
lower condensing pressure
Methods of Capacity Control
There are many methods of capacity control for semi-hermetic compressors but Emerson Climate Technologies uses the
“Blocked Suction method”.
NOTE: Oil circulation in systems with capacity control is more critical.
Advantages:
• Reduces the starting frequency of the compressors;
• Ensure satisfactory operation with optimal capacity data;
• Energy cost saving even at partial load.
Disadvantages:
• Motor is less cooled (refrigerant ow reduced);
• Restriction of the application range;
• Oil circulation is more critical.
All Stream compressor models can be equipped with a mechanical capacity control. Be aware that capacity-controlled
operation changes the application range of the compressor.
Capacity Control
Capacity-controlled 4M* and 6M* compressors work on the principle of blocking the suction gas passage to two or more cylinders. They
require the use of a special cylinder head, a control valve with solenoid coil, and a special valve plate, too. These items may be ordered
factory- installed or in kit form for later installation.
Inactive Capacity Control
To prevent transport damage the solenoid valves are supplied loose with the compressor and the cylinder head is tted with a shipping
plate. All capacity-control prepared cylinder heads on 4- and 6-cylinder Stream compressors are delivered with the mounted inactive
gasket for the capacity controlled port. This will ensure full capacity operation of the compressor if the solenoid control valve is not
installed for any reason. To activate the capacity control, the blind ange and the inactive gasket have to be removed and to be replaced
by the solenoid control valve and the active gasket which is provided with a control valve kit.