NATE Industry Competency Exam: Commercial
Refrigeration – Qs And As
With the condensing pressure and compressor speed remaining constant, a
decrease in suction pressure will cause a(n):
a. Decrease in compressor capacity and decrease in current.
b. Increase in compressor capacity and decrease in current.
c. Increase in compressor capacity and increase in current.
d. Decrease in compressor capacity and increase in current. ✔️Ans - D
An indication of non-condensable gas in a refrigeration system is significantly:
a. Lower-than-normal suction pressures.
b. higher-than-normal suction pressures.
c. Lower-than-normal head pressures.
d. higher-than-normal head pressures. ✔️Ans - D
An automatic expansion valve controls refrigerant flow to an evaporator by
maintaining a constant:
a. Suction pressure.
b. Pressure differential across the valve port.
c. Liquid line pressure.
d. Superheat. ✔️Ans - A
What is the approximate compression ratio of a compressor operating at 35
psig suction pressure and 135 psig discharge pressure?
a. 1:03.
b. 3:01.
c. 1:04.
d. 4:01. ✔️Ans - B
The BTUs rejected at the condenser are always greater than the heat absorbed
in the evaporator because:
a. The condenser is mounted outside with restricted airflow.
,b. Of the high temperature of the discharge vapor and length of the discharge
line.
c. Of the inefficiency of the condenser and pressure drop in the discharge line.
d. Of the heat of compression in the compressor. ✔️Ans - D
A unit cooler is inspected and found to be completely iced up. The heaters and
defrost timer are found to be working properly. A technician should:
a. Adjust the defrost termination switch to a higher temperature setting.
b. Adjust the thermostatic expansion valve to a higher superheat setting.
c. Clear all of the ice from the coil and find out why the coil is frosted.
d. Increase the frequency of the defrost cycle. ✔️Ans - A
what is the correct gauge pressure corresponding to an absolute pressure of
24.7 psia at sea level?
a. 10 psig.
b. 12.6 psig.
c. 39.4 psig.
d. 39.7 psig. ✔️Ans - A
For a lineup of medium temperature case, an evaporator temperature 0f 23°F
is needed. The following conditions exist:
· The suction line pressure drop is equivalent to approximately 2°F.
· The liquid line pressure drop is equivalent to 1°F.
The compressor capacity should be selected based on a saturated suction
temperature of:
a. 20°F.
b. 21°F.
c. 23°F.
d. 25°F. ✔️Ans - B
What is true of systems with multiple evaporators at different temperatures?
a. It is required to install evaporator pressure regulator(s).
b. The compressor discharge pressure will be a function of the coldest space.
c. It is required to install a head pressure control valve.
d. It is required to install a crankcase pressure regulator. ✔️Ans - A
, If charging a system by subcooling, what metering devices is installed?
a. Capillary tube.
b. Restrictor.
c. Thermostatic expansion valve.
d. Fixed orifice. ✔️Ans - C
The most critical refrigerant line with respect to sizing for compressor
performance is the:
a. Liquid line.
b. Discharge line.
c. Suction line.
d. Bypass line. ✔️Ans - C
In a liquid line, excess pressure drop can cause:
a. Sweating suction lines.
b. Flash gas.
c. Compressor overload.
d. Liquid subcooling. ✔️Ans - B
What are the two factors making up the safety classification for refrigerants?
a. Toxicity and time weighted average.
b. Toxicity and flammability.
c. Emergency exposure limit and time weighted average.
d. Flammability and TEWI. ✔️Ans - B
What would be most affected by the use of an oversized suction line?
a. Discharge temperature.
b. Oil return.
c. Return gas temperature.
d. Refrigerant migration. ✔️Ans - B
On an electrical diagram, the below symbol represents a control that:
Refrigeration – Qs And As
With the condensing pressure and compressor speed remaining constant, a
decrease in suction pressure will cause a(n):
a. Decrease in compressor capacity and decrease in current.
b. Increase in compressor capacity and decrease in current.
c. Increase in compressor capacity and increase in current.
d. Decrease in compressor capacity and increase in current. ✔️Ans - D
An indication of non-condensable gas in a refrigeration system is significantly:
a. Lower-than-normal suction pressures.
b. higher-than-normal suction pressures.
c. Lower-than-normal head pressures.
d. higher-than-normal head pressures. ✔️Ans - D
An automatic expansion valve controls refrigerant flow to an evaporator by
maintaining a constant:
a. Suction pressure.
b. Pressure differential across the valve port.
c. Liquid line pressure.
d. Superheat. ✔️Ans - A
What is the approximate compression ratio of a compressor operating at 35
psig suction pressure and 135 psig discharge pressure?
a. 1:03.
b. 3:01.
c. 1:04.
d. 4:01. ✔️Ans - B
The BTUs rejected at the condenser are always greater than the heat absorbed
in the evaporator because:
a. The condenser is mounted outside with restricted airflow.
,b. Of the high temperature of the discharge vapor and length of the discharge
line.
c. Of the inefficiency of the condenser and pressure drop in the discharge line.
d. Of the heat of compression in the compressor. ✔️Ans - D
A unit cooler is inspected and found to be completely iced up. The heaters and
defrost timer are found to be working properly. A technician should:
a. Adjust the defrost termination switch to a higher temperature setting.
b. Adjust the thermostatic expansion valve to a higher superheat setting.
c. Clear all of the ice from the coil and find out why the coil is frosted.
d. Increase the frequency of the defrost cycle. ✔️Ans - A
what is the correct gauge pressure corresponding to an absolute pressure of
24.7 psia at sea level?
a. 10 psig.
b. 12.6 psig.
c. 39.4 psig.
d. 39.7 psig. ✔️Ans - A
For a lineup of medium temperature case, an evaporator temperature 0f 23°F
is needed. The following conditions exist:
· The suction line pressure drop is equivalent to approximately 2°F.
· The liquid line pressure drop is equivalent to 1°F.
The compressor capacity should be selected based on a saturated suction
temperature of:
a. 20°F.
b. 21°F.
c. 23°F.
d. 25°F. ✔️Ans - B
What is true of systems with multiple evaporators at different temperatures?
a. It is required to install evaporator pressure regulator(s).
b. The compressor discharge pressure will be a function of the coldest space.
c. It is required to install a head pressure control valve.
d. It is required to install a crankcase pressure regulator. ✔️Ans - A
, If charging a system by subcooling, what metering devices is installed?
a. Capillary tube.
b. Restrictor.
c. Thermostatic expansion valve.
d. Fixed orifice. ✔️Ans - C
The most critical refrigerant line with respect to sizing for compressor
performance is the:
a. Liquid line.
b. Discharge line.
c. Suction line.
d. Bypass line. ✔️Ans - C
In a liquid line, excess pressure drop can cause:
a. Sweating suction lines.
b. Flash gas.
c. Compressor overload.
d. Liquid subcooling. ✔️Ans - B
What are the two factors making up the safety classification for refrigerants?
a. Toxicity and time weighted average.
b. Toxicity and flammability.
c. Emergency exposure limit and time weighted average.
d. Flammability and TEWI. ✔️Ans - B
What would be most affected by the use of an oversized suction line?
a. Discharge temperature.
b. Oil return.
c. Return gas temperature.
d. Refrigerant migration. ✔️Ans - B
On an electrical diagram, the below symbol represents a control that:
