Unit Review : Refrigeration & AC System Controls Comprehensive Self-Assessment

Question 1

1.	With the indirect type of temperature-actuated refrigeration control the bulb is installed in the \_\_\_\_\_ while the remainder of the control is located outside in a convenient location.
A.	Evaporator
B.	Condenser
C.	Refrigerator
D.	Receiver
E.	Refrigerated space

Answer 1

E. Refrigerated space

Question 2

2. On larger capacity refrigeration compressors the _____ valves prior to starting.
   A. Open the suction and discharge
   B. Close the suction and open the discharge
   C. Open the suction and close the discharge
   D. Close the suction and discharge
   E. Open the bypass

Answer 2

B. Close the suction and open the discharge

Question 3

3. What is the symptom of a refrigeration system when the compressor runs continuously due to a lack of refrigerant?
   A. Excessive load
   B. Bubbles in the sight glass
   C. High discharge pressure
   D. Low temperature of substance to be cooled
   E. Thermostat set too low

Answer 3

B. Bubbles in the sight glass

Question 4

4.	The CSA B52 Mechanical Refrigeration Code requires that all refrigeration systems containing more than \_\_\_\_\_ kg of refrigerant and operating above atmospheric pressure shall be equipped with a pressure limiting device.
A.	5 kg (11 lb)
B.	15 kg (33.1 lb)
C.	9 kg (19.8 lb)
D.	20 kg (44.1 lb)
E.	12 kg (26.4 lb)

Answer 4

C. 9 kg (19.8 lb)

Question 5

5. The charge of refrigerant in a system with a high-pressure float valve is critical. Too much refrigerant in the evaporator may cause:
   A. Vapour to be carried over to the compressor with the liquid
   B. Liquid to be carried over to the compressor with the vapour
   C. Liquid to be carried over to the condenser with the vapour
   D. Vapour to be carried over to the condenser with the liquid
   E. Liquid to be carried over to the receiver with the vapour

Answer 5

B. Liquid to be carried over to the compressor with the vapour

Question 6

6. One of the disadvantages of evaporator capacity control by face damper is that the:
   A. Air volume to the space is reduced
   B. Refrigerant volume to the space is reduced
   C. Temperature of the space is reduced
   D. Temperature of the space is increased
   E. Refrigerant pressure to the space is reduced

Answer 6

A. Air volume to the space is reduced

Question 7

7.	An automatic expansion or constant pressure valve is suitable when compressors are controlled by a:
A.	Pressurestat
B.	Humidistat
C.	Thermostat
D.	Rheostat
E.	Aquastat

Answer 7

C. Thermostat

Question 8

8. What is the purpose of the weighted valve pin” used with a high-pressure float valve?
   A. Control the flow of refrigerant into the evaporator
   B. Control the flow of refrigerant into the condenser
   C. Maintain a back pressure in the condenser
   D. Control the pressure in the refrigeration system
   E. Reduce the amount of line frosting after the float valve

Answer 8

E. Reduce the amount of line frosting after the float valve

Question 9

9.	The pressure-actuated refrigeration control is actuated by the:
A.	Discharge pressure of the compressor
B.	Suction pressure of the condenser
C.	Discharge pressure of the receiver
D.	Suction temperature of the compressor
E.	Suction pressure of the compressor

Answer 9

E. Suction pressure of the compressor

Question 10

10.	A pressure-actuated refrigeration control cannot be used in conjunction with a/an \_\_\_\_\_ expansion valve
A.	Automatic
B.	Thermostatic
C.	Hand
D.	Humidity
E.	Solenoid

Answer 10

A. Automatic

Question 11

11.	One of the three distinct classes of refrigeration controls is the \_\_\_\_\_ control.
A.	Temperature actuated
B.	Actuating or secondary
C.	Pressure actuated
D.	Humidity actuated
E.	Solenoid

Answer 11

B. Actuating or secondary

Question 12

12. Motor overload protection is a manual reset device that will take the motor itself offline when the current drawn by the motor exceeds:
    A. Its minimum allowable value
    B. Its maximum allowable value
    C. The condenser maximum allowable pressure
    D. The evaporator maximum allowable temperature
    E. Its maximum allowable oil temperature

Answer 12

B. Its maximum allowable value

Question 13

13. Why must you avoid running a refrigeration system below 14 KPa when pumping down?
    A. A slightly positive system pressure is required to prevent air infiltration
    B. Too much refrigerant will be required for a recharge
    C. The compressor will need to be stopped to prevent it running dry
    D. The systems heat exchangers will ice up
    E. The heat exchanges may collapse due to the low pressure

Answer 13

A. A slightly positive system pressure is required to prevent air infiltration

Question 14

14. What is the symptom of a refrigeration system when the compressor discharge pressure is too high due to the improper operation错误操作of the evaporative condenser?
    A. Very hot condenser
    B. Fouled tubes in shell and tube condenser
    C. Non-condensables in system
    D. Overcharge of refrigerant
    E. Scaled coil surface

Answer 14

E. Scaled coil surface

Question 15

15. The low-pressure side is isolated when its minimum design pressure is reached and then the pressurizing gas is admitted to the refrigeration system high-pressure side and increased to the required:
    A. High-pressure side minimum design pressure
    B. Low-pressure side operating pressure
    C. High-pressure side operating pressure
    D. Low-pressure side minimum design pressure
    E. High-pressure side maximum design pressure

Answer 15

A. High-pressure side minimum design pressure

Question 16

16.	The high oil temperature cutout is a safety control that shuts down the compressor when the lubricating oil temperature becomes too high due to:
A.	Loss of refrigerant
B.	Evaporator high temperature
C.	Condenser high pressure
D.	Condenser high temperature
E.	Loss of oil cooling

Answer 16

E. Loss of oil cooling

Question 17

17.	The vane closed switch is in the motor starting circuit so that the compressor can only be started when the vanes are in the \_\_\_\_\_ position.
A.	Evaporator open
B.	Compressor closed
C.	Compressor open
D.	Evaporator closed
E.	Closed position

Answer 17

E. Closed position

Question 18

18.	One of the most important secondary controls in a refrigerating system is the refrigerant flow control used to regulate the amount of liquid refrigerant flowing into the:
A.	Refrigerator
B.	Condenser
C.	Evaporator
D.	Receiver
E.	Refrigerated space

Answer 18

C. Evaporator

Question 19

19. The information card that code requires for refrigeration systems over 125 kW must include all of the following information except:
    A. Instructions for shutting down the system in case of emergency
    B. Instructions for starting up the system in case of emergency
    C. The name, address and day and night telephone numbers for obtaining service
    D. The name, address, and telephone number of the regulatory authority
    E. Instructions to notify said authority immediately in case of emergency

Answer 19

B. Instructions for starting up the system in case of emergency

Question 20

20. The refrigerant low temperature cutout is a safety low limit thermostat that senses the:
    A. Water temperature in the chiller
    B. Refrigerant temperature in the condenser
    C. Refrigerant temperature in the chiller
    D. Water temperature in the evaporator
    E. Refrigerant pressure in the chiller

Answer 20

C. Refrigerant temperature in the chiller