Unit 25
The one-time relief valve is caused to relieve by ____________________.
temperature
Random defrost is accomplished ____.
when the refrigeration system has enough reserve capacity to cool more than the load requirement
Which of the following is another type of low-ambient temperature head pressure control?
Air volume control using shutters and fan cycling.
How does the receiver ensure that only 100% liquid refrigerant enters the liquid line?
By means of a dip tube.
To protect the compressor during periods of hot pull down, a(n) ____ valve is used.
CPR (crankcase pressure regulator)
Which of the following is a type of low-ambient temperature head pressure control?
Fan cycling.
EPR valves are also referred to as ____ valves.
ORI
____ are snap-acting valves that open and close very fast when the electrical energy is applied to the coil.
Solenoid valves
Technician "A" says that a multi-evaporator system equipped with three evaporators (one high temperature, one medium temperature, and one low temperature) will use one evaporator pressure regulator and two flow check valves. Technician "B" says that the crankcase pressure regulator is used to keep the low-temperature compressor from overloading on a hot pulldown. Which of the following statements is correct?
Technician "A" is incorrect. Technician "B" is correct.
Discuss the king valve.
The king valve is located in the liquid line between the receiver and the expansion valve. It is often fastened to the receiver tank at the outlet.
What is the temperature range in medium-temperature refrigeration?
The medium-temperature refrigeration coil normally operates below freezing and rises above freezing during the off cycle. A typical temperature range would be from 34 ºF to 45 ºF inside the cooler.
Where is the refrigerant filter drier found?
The refrigerant filter drier can be found at any point on the liquid line after the king valve.
Where is the refrigerant sight glass normally located?
The refrigerant sight glass is normally located anywhere liquid flow exists and anywhere it can serve a purpose.
What are the two forces that control the EPR valve?
The two forces that control the EPR valve are the evaporator pressure, which is the valve's inlet pressure, and the valve's spring pressure.
What prevents the oil pressure safety control from de-energizing a compressor immediately after start-up?
There is a 90-second time delay.
Refrigeration systems are designed to operate year round. For this reason they are equipped with ____.
a low-ambient control
The normal position for a suction service valve during normal operation is ____.
a. back-seated b. front seated c. midseated d. Any of the three.
Frequently on smaller condensing units, one fan will run continuously and the other fan will be cycled on and off with a(n) ____.
ambient temperature controller
The ____________________ is a mechanical control that keeps the refrigerant pressure in the evaporator from going below a predetermined point.
evaporator pressure-regulating valve (EPR valve) evaporator pressure-regulating valve EPR valve
To protect a refrigeration compressor when refrigerant loss occurs, a(n) ____________________ control is used.
low pressure
Two-temperature operation of a refrigeration system is necessary when ____.
more than one evaporator is used with a compressor
Two types of relief valves are the spring-loaded valve and the ____________________ valve.
one-time One time
