NATE COMMERCIAL REFRIGERATION SPECIALTY EXAM NEWEST EVALUATED
EXAM PRACTICE 120 QUESTIONS 2026-2027|ORIGINAL QUESTIONS &
ANSWERS |DETAILED RATIONALES |HINTED COMPLETE EXAM PREP GRADED
A+*INSTANT DOWNLOAD PDF*
1. 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
Answer: B
Explanation: Compression ratio is calculated as absolute discharge pressure
divided by absolute suction pressure. (135 + 14.7) ÷ (35 + 14.7) = 149.7 ÷ 49.7 ≈
3:1. This represents a typical medium-temperature commercial refrigeration
compression ratio.
2. 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
Answer: D
Explanation: The heat of compression is added to the refrigerant during the
compression process. Total heat rejected at the condenser equals the heat
,absorbed in the evaporator plus the heat equivalent of the compressor work
(heat of compression).
3. 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
Answer: A
Explanation: If the defrost heaters and timer are functioning but ice persists,
the defrost termination switch may be terminating the defrost cycle before all
ice is melted. Adjusting it to a higher temperature setting allows the defrost
cycle to continue longer.
4. 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
Answer: A
Explanation: Gauge pressure = Absolute pressure − Atmospheric pressure at
sea level (14.7 psi). 24.7 − 14.7 = 10 psig. This is a fundamental pressure
relationship used in refrigerant charging and diagnostics.
,5. For a lineup of medium temperature cases, an evaporator temperature of
23°F is needed. 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
Answer: B
Explanation: Suction line pressure drop reduces the pressure (and
corresponding saturated temperature) at the compressor. The compressor
must be selected at a saturated suction temperature lower than the
evaporator temperature by the amount of suction line pressure drop: 23°F −
2°F = 21°F.
6. 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 decrease in current
Answer: D
Explanation: Lower suction pressure means lower refrigerant density entering
the compressor, reducing the mass flow rate and therefore compressor
capacity. Lower mass flow also reduces the compressor amp draw (current).
, 7. 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
Answer: D
Explanation: Non-condensable gases (such as air) do not condense in the
condenser. They accumulate on the high side, raising the discharge/head
pressure significantly above normal for the given ambient conditions.
8. 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
Answer: A
Explanation: An automatic expansion valve (AEV) maintains a constant
evaporator pressure by modulating refrigerant flow in response to suction
pressure changes, regardless of load variations.
EXAM PRACTICE 120 QUESTIONS 2026-2027|ORIGINAL QUESTIONS &
ANSWERS |DETAILED RATIONALES |HINTED COMPLETE EXAM PREP GRADED
A+*INSTANT DOWNLOAD PDF*
1. 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
Answer: B
Explanation: Compression ratio is calculated as absolute discharge pressure
divided by absolute suction pressure. (135 + 14.7) ÷ (35 + 14.7) = 149.7 ÷ 49.7 ≈
3:1. This represents a typical medium-temperature commercial refrigeration
compression ratio.
2. 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
Answer: D
Explanation: The heat of compression is added to the refrigerant during the
compression process. Total heat rejected at the condenser equals the heat
,absorbed in the evaporator plus the heat equivalent of the compressor work
(heat of compression).
3. 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
Answer: A
Explanation: If the defrost heaters and timer are functioning but ice persists,
the defrost termination switch may be terminating the defrost cycle before all
ice is melted. Adjusting it to a higher temperature setting allows the defrost
cycle to continue longer.
4. 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
Answer: A
Explanation: Gauge pressure = Absolute pressure − Atmospheric pressure at
sea level (14.7 psi). 24.7 − 14.7 = 10 psig. This is a fundamental pressure
relationship used in refrigerant charging and diagnostics.
,5. For a lineup of medium temperature cases, an evaporator temperature of
23°F is needed. 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
Answer: B
Explanation: Suction line pressure drop reduces the pressure (and
corresponding saturated temperature) at the compressor. The compressor
must be selected at a saturated suction temperature lower than the
evaporator temperature by the amount of suction line pressure drop: 23°F −
2°F = 21°F.
6. 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 decrease in current
Answer: D
Explanation: Lower suction pressure means lower refrigerant density entering
the compressor, reducing the mass flow rate and therefore compressor
capacity. Lower mass flow also reduces the compressor amp draw (current).
, 7. 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
Answer: D
Explanation: Non-condensable gases (such as air) do not condense in the
condenser. They accumulate on the high side, raising the discharge/head
pressure significantly above normal for the given ambient conditions.
8. 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
Answer: A
Explanation: An automatic expansion valve (AEV) maintains a constant
evaporator pressure by modulating refrigerant flow in response to suction
pressure changes, regardless of load variations.
