Master Refrigeration Technician Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A commercial refrigeration system using R-404A is experiencing low
suction pressure, high superheat, and reduced cooling capacity. The
technician suspects a refrigerant charge issue. Which diagnostic
procedure would most accurately confirm undercharge versus a
restricted metering device?
A. Measure compressor amperage only under full load conditions
B. Compare evaporator outlet temperature with condenser subcooling and
evaluate system superheat across multiple load conditions
C. Inspect only the liquid line sight glass for bubbles and immediately add
refrigerant
D. Replace the expansion valve without performing additional diagnostics
The most reliable method is to evaluate both superheat and subcooling
across operating conditions because undercharge typically shows high
,superheat with low subcooling, while a restriction often causes abnormal
temperature drops across the metering device; relying on a single symptom
or replacing components without full analysis can lead to misdiagnosis.
2. In a vapor-compression system, what is the primary thermodynamic
purpose of the compressor?
A. To increase refrigerant enthalpy by adding latent heat
B. To decrease refrigerant temperature before entering the evaporator
C. To raise refrigerant pressure and temperature to enable heat rejection at
the condenser
D. To control refrigerant mass flow rate into the evaporator
The compressor’s primary function is to elevate refrigerant pressure and
temperature so that it can reject heat effectively in the condenser; it does
not directly add latent heat or regulate evaporator flow.
3. A technician observes frost forming only on the first half of an
evaporator coil while the rest remains warm. Which condition is most
likely responsible?
A. Overfeeding expansion valve
B. Low airflow across the evaporator
C. Uniform refrigerant distribution with correct charge
D. Excessively high condenser subcooling
,Partial frost formation on the inlet section of the evaporator typically
indicates restricted refrigerant flow or low charge, causing early boiling
and insufficient refrigerant distribution throughout the coil.
4. What is the most likely effect of excessive subcooling in a refrigeration
system?
A. Increased evaporator pressure and reduced compressor load
B. Reduced flash gas in the liquid line and improved metering stability
C. Increased superheat and reduced cooling capacity
D. Immediate compressor failure due to liquid slugging
Excessive subcooling generally ensures a solid column of liquid refrigerant
with minimal flash gas, improving expansion device performance and
system stability, though excessively high values may indicate overcharging
or condenser issues.
5. A scroll compressor is making abnormal noise and has intermittent
capacity loss. Which failure mode is most consistent with internal
scroll damage?
A. High evaporator airflow
B. Loss of suction pressure due to overcharge
C. Worn or damaged scroll elements causing internal bypassing of refrigerant
D. Excessive condenser fan speed
, Damaged scroll elements can allow internal leakage paths, reducing
compression efficiency and causing noise and fluctuating capacity as
refrigerant bypasses compression stages.
6. In a refrigeration cycle, what is the function of the thermostatic
expansion valve (TXV)?
A. To increase refrigerant pressure before the condenser
B. To regulate evaporator superheat by controlling refrigerant flow
C. To compress refrigerant vapor into liquid state
D. To remove moisture from the refrigerant
A TXV maintains proper evaporator performance by modulating
refrigerant flow based on superheat, ensuring efficient boiling without
flooding or starving the coil.
7. A system operating with a dirty condenser coil will most likely
experience which condition?
A. Low head pressure and high subcooling
B. High head pressure and increased compressor work
C. Low suction pressure and reduced evaporator frost
D. Reduced refrigerant charge requirement
A dirty condenser restricts heat rejection, raising head pressure and forcing
the compressor to work harder, increasing energy consumption and system
stress.
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A commercial refrigeration system using R-404A is experiencing low
suction pressure, high superheat, and reduced cooling capacity. The
technician suspects a refrigerant charge issue. Which diagnostic
procedure would most accurately confirm undercharge versus a
restricted metering device?
A. Measure compressor amperage only under full load conditions
B. Compare evaporator outlet temperature with condenser subcooling and
evaluate system superheat across multiple load conditions
C. Inspect only the liquid line sight glass for bubbles and immediately add
refrigerant
D. Replace the expansion valve without performing additional diagnostics
The most reliable method is to evaluate both superheat and subcooling
across operating conditions because undercharge typically shows high
,superheat with low subcooling, while a restriction often causes abnormal
temperature drops across the metering device; relying on a single symptom
or replacing components without full analysis can lead to misdiagnosis.
2. In a vapor-compression system, what is the primary thermodynamic
purpose of the compressor?
A. To increase refrigerant enthalpy by adding latent heat
B. To decrease refrigerant temperature before entering the evaporator
C. To raise refrigerant pressure and temperature to enable heat rejection at
the condenser
D. To control refrigerant mass flow rate into the evaporator
The compressor’s primary function is to elevate refrigerant pressure and
temperature so that it can reject heat effectively in the condenser; it does
not directly add latent heat or regulate evaporator flow.
3. A technician observes frost forming only on the first half of an
evaporator coil while the rest remains warm. Which condition is most
likely responsible?
A. Overfeeding expansion valve
B. Low airflow across the evaporator
C. Uniform refrigerant distribution with correct charge
D. Excessively high condenser subcooling
,Partial frost formation on the inlet section of the evaporator typically
indicates restricted refrigerant flow or low charge, causing early boiling
and insufficient refrigerant distribution throughout the coil.
4. What is the most likely effect of excessive subcooling in a refrigeration
system?
A. Increased evaporator pressure and reduced compressor load
B. Reduced flash gas in the liquid line and improved metering stability
C. Increased superheat and reduced cooling capacity
D. Immediate compressor failure due to liquid slugging
Excessive subcooling generally ensures a solid column of liquid refrigerant
with minimal flash gas, improving expansion device performance and
system stability, though excessively high values may indicate overcharging
or condenser issues.
5. A scroll compressor is making abnormal noise and has intermittent
capacity loss. Which failure mode is most consistent with internal
scroll damage?
A. High evaporator airflow
B. Loss of suction pressure due to overcharge
C. Worn or damaged scroll elements causing internal bypassing of refrigerant
D. Excessive condenser fan speed
, Damaged scroll elements can allow internal leakage paths, reducing
compression efficiency and causing noise and fluctuating capacity as
refrigerant bypasses compression stages.
6. In a refrigeration cycle, what is the function of the thermostatic
expansion valve (TXV)?
A. To increase refrigerant pressure before the condenser
B. To regulate evaporator superheat by controlling refrigerant flow
C. To compress refrigerant vapor into liquid state
D. To remove moisture from the refrigerant
A TXV maintains proper evaporator performance by modulating
refrigerant flow based on superheat, ensuring efficient boiling without
flooding or starving the coil.
7. A system operating with a dirty condenser coil will most likely
experience which condition?
A. Low head pressure and high subcooling
B. High head pressure and increased compressor work
C. Low suction pressure and reduced evaporator frost
D. Reduced refrigerant charge requirement
A dirty condenser restricts heat rejection, raising head pressure and forcing
the compressor to work harder, increasing energy consumption and system
stress.
