Iowa HVAC Technician Examination
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A heat pump operating in heating mode has a suction pressure significantly
lower than expected, while the superheat is high and the liquid-line
temperature is normal. Which condition is most likely?
A. Overcharge
B. Restricted evaporator airflow
C. Refrigerant undercharge
D. Noncondensable gases
Correct answer: Refrigerant undercharge
Rationale: An undercharged system commonly produces low suction pressure,
high superheat, and reduced evaporator capacity because insufficient
refrigerant is available to fully load the evaporator.
, 2. What is the primary purpose of measuring evaporator superheat on a fixed-
orifice refrigeration system?
A. To determine condenser subcooling
B. To verify compressor oil level
C. To evaluate refrigerant feeding and evaporator outlet conditions
D. To determine electrical phase rotation
Correct answer: To evaluate refrigerant feeding and evaporator outlet
conditions
Rationale: Superheat indicates how much the refrigerant vapor temperature has
risen above its saturation temperature at the evaporator outlet and helps
identify underfeeding, overfeeding, or airflow problems.
3. A condensing unit has a high head pressure, high subcooling, and normal-
to-low suction pressure. Which condition should be investigated first?
A. Low refrigerant charge
B. Liquid-line restriction
C. Excessive evaporator airflow
D. Compressor undercompression
Correct answer: Liquid-line restriction
Rationale: A restriction can trap refrigerant upstream, causing high subcooling
and elevated condensing pressure while starving the evaporator and reducing
suction pressure.
4. What is the most important reason for maintaining proper airflow across an
air-conditioning evaporator?
A. It prevents compressor oil migration
B. It ensures proper heat transfer and prevents abnormal coil conditions
C. It increases refrigerant pressure
D. It eliminates the need for superheat measurements
,Correct answer: It ensures proper heat transfer and prevents abnormal coil
conditions
Rationale: Correct airflow is essential for transferring indoor heat to the
refrigerant. Insufficient airflow can cause coil icing, low suction pressure,
reduced capacity, and possible compressor damage.
5. A 24-volt control circuit has a 40 VA transformer. Approximately how much
current can the transformer safely supply at its rated capacity?
A. 0.6 A
B. 1.0 A
C. 1.67 A
D. 2.4 A
Correct answer: 1.67 A
Rationale: Transformer current is calculated as VA ÷ volts. 40 VA ÷ 24 V =
approximately 1.67 A.
6. What is the primary function of a crankcase heater on a refrigeration
compressor?
A. Increase compressor discharge pressure
B. Prevent refrigerant migration and dilution of compressor oil during shutdown
C. Increase evaporator pressure
D. Reduce condenser subcooling
Correct answer: Prevent refrigerant migration and dilution of compressor oil
during shutdown
Rationale: A crankcase heater keeps the compressor oil warm enough to
discourage refrigerant from migrating into and condensing in the crankcase
during off cycles.
7. When using a micron gauge to evacuate a refrigeration system, where
should the gauge ideally be connected?
, A. Only at the recovery cylinder
B. At a location representative of the system vacuum, preferably away from the
pump
C. Directly to the pump inlet only
D. On the compressor discharge line
Correct answer: At a location representative of the system vacuum, preferably
away from the pump
Rationale: Measuring only at the pump can give a misleading indication because
restrictions in hoses and fittings can cause the pump to read a deeper vacuum
than exists in the system.
8. Why should a technician avoid using the system's compressor as a vacuum
pump?
A. It produces excessive subcooling
B. Air and moisture can damage the compressor, and compressors are not
designed for deep evacuation
C. It causes the thermostat to open
D. It increases condenser airflow
Correct answer: Air and moisture can damage the compressor, and compressors
are not designed for deep evacuation
Rationale: A compressor is designed to compress refrigerant, not evacuate air
and moisture from a system. Operating under deep vacuum can cause
lubrication and electrical problems.
9. What does a high evaporator superheat combined with low suction
pressure usually indicate?
A. Evaporator starvation
B. Excessive refrigerant charge
C. Flooded evaporator
D. Excessive condenser airflow
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A heat pump operating in heating mode has a suction pressure significantly
lower than expected, while the superheat is high and the liquid-line
temperature is normal. Which condition is most likely?
A. Overcharge
B. Restricted evaporator airflow
C. Refrigerant undercharge
D. Noncondensable gases
Correct answer: Refrigerant undercharge
Rationale: An undercharged system commonly produces low suction pressure,
high superheat, and reduced evaporator capacity because insufficient
refrigerant is available to fully load the evaporator.
, 2. What is the primary purpose of measuring evaporator superheat on a fixed-
orifice refrigeration system?
A. To determine condenser subcooling
B. To verify compressor oil level
C. To evaluate refrigerant feeding and evaporator outlet conditions
D. To determine electrical phase rotation
Correct answer: To evaluate refrigerant feeding and evaporator outlet
conditions
Rationale: Superheat indicates how much the refrigerant vapor temperature has
risen above its saturation temperature at the evaporator outlet and helps
identify underfeeding, overfeeding, or airflow problems.
3. A condensing unit has a high head pressure, high subcooling, and normal-
to-low suction pressure. Which condition should be investigated first?
A. Low refrigerant charge
B. Liquid-line restriction
C. Excessive evaporator airflow
D. Compressor undercompression
Correct answer: Liquid-line restriction
Rationale: A restriction can trap refrigerant upstream, causing high subcooling
and elevated condensing pressure while starving the evaporator and reducing
suction pressure.
4. What is the most important reason for maintaining proper airflow across an
air-conditioning evaporator?
A. It prevents compressor oil migration
B. It ensures proper heat transfer and prevents abnormal coil conditions
C. It increases refrigerant pressure
D. It eliminates the need for superheat measurements
,Correct answer: It ensures proper heat transfer and prevents abnormal coil
conditions
Rationale: Correct airflow is essential for transferring indoor heat to the
refrigerant. Insufficient airflow can cause coil icing, low suction pressure,
reduced capacity, and possible compressor damage.
5. A 24-volt control circuit has a 40 VA transformer. Approximately how much
current can the transformer safely supply at its rated capacity?
A. 0.6 A
B. 1.0 A
C. 1.67 A
D. 2.4 A
Correct answer: 1.67 A
Rationale: Transformer current is calculated as VA ÷ volts. 40 VA ÷ 24 V =
approximately 1.67 A.
6. What is the primary function of a crankcase heater on a refrigeration
compressor?
A. Increase compressor discharge pressure
B. Prevent refrigerant migration and dilution of compressor oil during shutdown
C. Increase evaporator pressure
D. Reduce condenser subcooling
Correct answer: Prevent refrigerant migration and dilution of compressor oil
during shutdown
Rationale: A crankcase heater keeps the compressor oil warm enough to
discourage refrigerant from migrating into and condensing in the crankcase
during off cycles.
7. When using a micron gauge to evacuate a refrigeration system, where
should the gauge ideally be connected?
, A. Only at the recovery cylinder
B. At a location representative of the system vacuum, preferably away from the
pump
C. Directly to the pump inlet only
D. On the compressor discharge line
Correct answer: At a location representative of the system vacuum, preferably
away from the pump
Rationale: Measuring only at the pump can give a misleading indication because
restrictions in hoses and fittings can cause the pump to read a deeper vacuum
than exists in the system.
8. Why should a technician avoid using the system's compressor as a vacuum
pump?
A. It produces excessive subcooling
B. Air and moisture can damage the compressor, and compressors are not
designed for deep evacuation
C. It causes the thermostat to open
D. It increases condenser airflow
Correct answer: Air and moisture can damage the compressor, and compressors
are not designed for deep evacuation
Rationale: A compressor is designed to compress refrigerant, not evacuate air
and moisture from a system. Operating under deep vacuum can cause
lubrication and electrical problems.
9. What does a high evaporator superheat combined with low suction
pressure usually indicate?
A. Evaporator starvation
B. Excessive refrigerant charge
C. Flooded evaporator
D. Excessive condenser airflow
