Trane TRG-TRC004-EN Air Compressor User Manual


  Open as PDF
of 55
 
TRG-TRC004-EN 19
period two
Compressor Capacity Control
notes
Cylinder Unloaders
Most large reciprocating compressors (above 10 tons [35 kW]) are fitted with
cylinder unloaders that are used to match the compressor’s refrigerant-
pumping capacity with the falling evaporator load, by progressively
deactivating piston–cylinder pairs.
The cylinder unloader shown in this example reciprocating compressor uses an
electrically-actuated unloader valve to close the suction passage to the cylinder
that is being unloaded.
In response to a decreasing load, an electronic controller sends a signal to open
a solenoid valve. This solenoid valve diverts pressurized refrigerant vapor from
the compressor discharge to the top of the unloader valve, causing the
unloader valve to close and shut off the flow of refrigerant vapor into the
cylinder. Even though the piston continues to travel back and forth inside this
cylinder, it is no longer performing compression since it cannot take in any
refrigerant vapor.
&\OLQGHU8QORDGHUV
XQORDGHU
XQORDGHU
YDOYH
YDOYH
UHIULJHUDQW
UHIULJHUDQW
YDSRU
YDSRU
GLVFKDUJH
GLVFKDUJH
XQORDGHU
XQORDGHU
VROHQRLGYDOYH
VROHQRLGYDOYH
FRQWUROOHU
FRQWUROOHU
F\OLQGHU
F\OLQGHU
SLVWRQ
SLVWRQ
Figure 29
 previous next