Question 3Refrigeration/AC - 1st Asst/Chief70% to pass
During operating periods of a multi-box refrigeration system using a capacity controlled compressor, when all of the evaporators of a four box plant are actively being fed with liquid refrigerant, the control oil pressure acting on the hydraulic relay piston will be at what value? Illustration GS-RA-13
AI Explanation
The correct answer is C) the highest.
When all the evaporators of a four-box refrigeration system are actively being fed with liquid refrigerant, the control oil pressure acting on the hydraulic relay piston will be at its highest value. This is because as the refrigeration load increases with all evaporators in use, the compressor capacity control system will need to increase the compressor displacement to meet the higher demand. This increase in compressor displacement requires the control oil pressure to be at its maximum to ensure the hydraulic relay piston is positioned to allow the compressor to operate at its highest capacity.
The other options are incorrect because the control oil pressure would not be at its lowest (A) or mid-range (B) when the refrigeration load is at its highest, and the lube oil system is indeed relevant to the operation of the capacity control unloader (D).
Related Questions
#1 Capacity control of a centrifugal refrigeration compressor can be accomplished by what means? #2 The fluid used as a source of actuating power against the underside of the unloader power element piston of the refrigeration compressor capacity control mechanism illustrated is obtained from where? Illustration GS-RA-13 #4 On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when the applied voltage and current draw associated with the normally open (NO) suction modulation valve located in the suction line both increase? #5 A refrigeration compressor used in a multi-box refrigeration system is designed with six of its eight cylinders able to be controlled for variable load conditions. If all of the reefer boxes are currently feeding, what percentage of the total number of compressor cylinders will be loaded after start up? #6 To prevent motor overload during start-up of a hermetically sealed centrifugal refrigeration system, what is true concerning the compressor suction gas variable inlet guide vanes?