Commercial Refrigeration Certification
In a dry type (direct expansion) evaporator, liquid refrigerant must boil away as close to the end of the coil as possible in order to:
A. operate at high efficiency.
B. ensure that frost does not accumulate.
C. sub-cool the compressor.
D. ensure proper oil return. - Answer A. operate at high efficiency.
The difference between the temperature of the refrigerant boiling in the evaporator and the temperature at the evaporator outlet is known as:
A. evaporator superheat.
B. latent heat.
C. evaporator sub-cooling.
D. sublimation. - Answer A. evaporator superheat.
An expansion device that is stuck open will cause:
A. low suction pressure
B. a starved evaporator.
C. excessive superheat
D. a flooded evaporator - Answer D. a flooded evaporator
When measuring evaporator superheat on a commercial system that has a long suction line, the pressure reading should be taken at the: A. compressor inlet.
B. evaporator outlet.
C. condenser outlet.
D. receiver Inlet. - Answer A. compressor inlet. (Suction Line)
Superheat measurements are best taken:
A. during a hot pull down.
B. at 8°F to 12°F.
C. during defrost.
D. with the system operating at design conditions. - Answer D. with the system operating at design conditions.
A technician is checking the superheat on a multi circuit evaporator and finds one of the circuits has a superheat that is higher than the others. This could be caused by:
A. a dirty coil.
B. a refrigerant overcharge
C. uneven air distribution.
D. a blocked distributor. - Answer D. a blocked distributor.
A TEV with an external equalizer is used on:
A. evaporators with a high pressure drop.
B. evaporators with a low pressure drop.
C. high temperature applications only.
D. all evaporators. - Answer A. evaporators with a high pressure drop.
Dry type evaporators operate most efficiently with a superheat setting of approximately:
A. 8° F to 12°F
B. 13° F to 19°F
C. 20° F to 30°F D. 31° F to 40° F - Answer A. 8° F to 12°F
An evaporator used to chill liquids in operating with a normal superheat setting, but the system is not cooling the product properly. Which of the following is the most likely cause?
A. overcharge of refrigerant
B. undercharge of refrigerant
C. the circulator
D. the TEV - Answer C. the circulator
What time interval is required between each superheat adjustment?
A. Not less than 1 hour
B. About 10-15 minutes
C. At least 1/2 hour.
D. No time delay. - Answer B. About 10-15 minutes
A low temperature evaporator used for cooling space or product refrigeration:
A. is the same as one used for medium or high temperatures.
B. must have fins spaced closer together.
C. must be frosted periodically.
D. must be defrosted periodically. - Answer D. must be defrosted periodically.
Some special applications use a flooded evaporator (operated full of refrigerant). In order to maintain the proper level of liquid refrigerant, a ____ type metering device is used.
A. TEV B. capillary tube
C. AEV
D. float - Answer D. float
A properly functioning condenser will first:
In a dry type (direct expansion) evaporator, liquid refrigerant must boil away as close to the end of the coil as possible in order to:
A. operate at high efficiency.
B. ensure that frost does not accumulate.
C. sub-cool the compressor.
D. ensure proper oil return. - Answer A. operate at high efficiency.
The difference between the temperature of the refrigerant boiling in the evaporator and the temperature at the evaporator outlet is known as:
A. evaporator superheat.
B. latent heat.
C. evaporator sub-cooling.
D. sublimation. - Answer A. evaporator superheat.
An expansion device that is stuck open will cause:
A. low suction pressure
B. a starved evaporator.
C. excessive superheat
D. a flooded evaporator - Answer D. a flooded evaporator
When measuring evaporator superheat on a commercial system that has a long suction line, the pressure reading should be taken at the: A. compressor inlet.
B. evaporator outlet.
C. condenser outlet.
D. receiver Inlet. - Answer A. compressor inlet. (Suction Line)
Superheat measurements are best taken:
A. during a hot pull down.
B. at 8°F to 12°F.
C. during defrost.
D. with the system operating at design conditions. - Answer D. with the system operating at design conditions.
A technician is checking the superheat on a multi circuit evaporator and finds one of the circuits has a superheat that is higher than the others. This could be caused by:
A. a dirty coil.
B. a refrigerant overcharge
C. uneven air distribution.
D. a blocked distributor. - Answer D. a blocked distributor.
A TEV with an external equalizer is used on:
A. evaporators with a high pressure drop.
B. evaporators with a low pressure drop.
C. high temperature applications only.
D. all evaporators. - Answer A. evaporators with a high pressure drop.
Dry type evaporators operate most efficiently with a superheat setting of approximately:
A. 8° F to 12°F
B. 13° F to 19°F
C. 20° F to 30°F D. 31° F to 40° F - Answer A. 8° F to 12°F
An evaporator used to chill liquids in operating with a normal superheat setting, but the system is not cooling the product properly. Which of the following is the most likely cause?
A. overcharge of refrigerant
B. undercharge of refrigerant
C. the circulator
D. the TEV - Answer C. the circulator
What time interval is required between each superheat adjustment?
A. Not less than 1 hour
B. About 10-15 minutes
C. At least 1/2 hour.
D. No time delay. - Answer B. About 10-15 minutes
A low temperature evaporator used for cooling space or product refrigeration:
A. is the same as one used for medium or high temperatures.
B. must have fins spaced closer together.
C. must be frosted periodically.
D. must be defrosted periodically. - Answer D. must be defrosted periodically.
Some special applications use a flooded evaporator (operated full of refrigerant). In order to maintain the proper level of liquid refrigerant, a ____ type metering device is used.
A. TEV B. capillary tube
C. AEV
D. float - Answer D. float
A properly functioning condenser will first:
