CO Solar Thermal Contractor Exam
Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant
Download Pdf.
1. Which component in a closed-loop solar thermal system is primarily
responsible for transferring heat collected by the solar collectors to
the building’s domestic hot-water or space-heating system without
mixing the two fluids?
A. Expansion tank
B. Differential controller
C. Heat exchanger
D. Air separator
C. Heat exchanger
A heat exchanger transfers thermal energy between the solar loop and
the load loop while keeping the two fluids physically separated. This is
especially important when the collector loop contains glycol or other
fluids that should not enter potable water.
2. In a typical active solar thermal system, what is the primary purpose
of a differential temperature controller?
,A. To maintain constant pressure in the collector loop
B. To operate the circulation pump when the collector is sufficiently
warmer than the storage tank
C. To regulate the expansion tank pressure
D. To prevent all water circulation during nighttime
B. To operate the circulation pump when the collector is sufficiently
warmer than the storage tank
A differential controller compares collector and storage temperatures
and activates the pump when there is a useful temperature difference,
allowing heat to move from the collectors to storage efficiently.
3. What is the principal purpose of an expansion tank in a closed-loop
solar thermal system?
A. To remove air from the system
B. To absorb fluid expansion caused by temperature increases
C. To increase collector efficiency
D. To reduce solar radiation
B. To absorb fluid expansion caused by temperature increases
Solar thermal fluids can expand substantially as system temperature
rises. A properly sized expansion tank accommodates this volume
change and helps prevent excessive pressure and relief-valve discharge.
4. Which type of solar thermal collector is generally most appropriate
for producing domestic hot water in moderate climates because of
its relatively simple construction and good performance?
,A. Flat-plate collector
B. Photovoltaic panel
C. Wind turbine
D. Evacuated electrical resistance panel
A. Flat-plate collector
Flat-plate collectors are widely used for domestic water heating because
they are durable, comparatively simple, and effective for the
temperature ranges commonly required for water heating.
5. What is the primary purpose of propylene glycol in many closed-
loop solar thermal systems?
A. To increase electrical conductivity
B. To provide freeze protection
C. To eliminate the need for an expansion tank
D. To prevent solar radiation from reaching the absorber
B. To provide freeze protection
Propylene glycol lowers the freezing point of the heat-transfer fluid,
helping protect collector piping and other components from freezing
damage in climates where temperatures can fall below 32°F (0°C).
6. Why must the concentration of glycol in a solar thermal system be
controlled carefully?
A. Excessive glycol concentration can reduce heat-transfer performance
and increase fluid viscosity
B. Glycol concentration has no effect on system operation
, C. Higher glycol concentration always increases efficiency
D. Glycol concentration determines the collector orientation
A. Excessive glycol concentration can reduce heat-transfer performance
and increase fluid viscosity
Increasing glycol concentration provides greater freeze protection but
also increases viscosity and can reduce heat-transfer efficiency. Proper
concentration must therefore balance freeze protection with pumping
and thermal performance.
7. Which device is normally installed to protect a pressurized solar
thermal system from excessive pressure?
A. Pressure relief valve
B. Check valve only
C. Thermometer
D. Balancing valve
A. Pressure relief valve
A pressure relief valve opens when system pressure reaches its set point,
protecting piping, collectors, storage tanks, and other components from
dangerous overpressure.
8. What is the main function of a check valve in a solar thermal
circulation system?
A. To measure fluid temperature
B. To prevent unwanted reverse flow
Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant
Download Pdf.
1. Which component in a closed-loop solar thermal system is primarily
responsible for transferring heat collected by the solar collectors to
the building’s domestic hot-water or space-heating system without
mixing the two fluids?
A. Expansion tank
B. Differential controller
C. Heat exchanger
D. Air separator
C. Heat exchanger
A heat exchanger transfers thermal energy between the solar loop and
the load loop while keeping the two fluids physically separated. This is
especially important when the collector loop contains glycol or other
fluids that should not enter potable water.
2. In a typical active solar thermal system, what is the primary purpose
of a differential temperature controller?
,A. To maintain constant pressure in the collector loop
B. To operate the circulation pump when the collector is sufficiently
warmer than the storage tank
C. To regulate the expansion tank pressure
D. To prevent all water circulation during nighttime
B. To operate the circulation pump when the collector is sufficiently
warmer than the storage tank
A differential controller compares collector and storage temperatures
and activates the pump when there is a useful temperature difference,
allowing heat to move from the collectors to storage efficiently.
3. What is the principal purpose of an expansion tank in a closed-loop
solar thermal system?
A. To remove air from the system
B. To absorb fluid expansion caused by temperature increases
C. To increase collector efficiency
D. To reduce solar radiation
B. To absorb fluid expansion caused by temperature increases
Solar thermal fluids can expand substantially as system temperature
rises. A properly sized expansion tank accommodates this volume
change and helps prevent excessive pressure and relief-valve discharge.
4. Which type of solar thermal collector is generally most appropriate
for producing domestic hot water in moderate climates because of
its relatively simple construction and good performance?
,A. Flat-plate collector
B. Photovoltaic panel
C. Wind turbine
D. Evacuated electrical resistance panel
A. Flat-plate collector
Flat-plate collectors are widely used for domestic water heating because
they are durable, comparatively simple, and effective for the
temperature ranges commonly required for water heating.
5. What is the primary purpose of propylene glycol in many closed-
loop solar thermal systems?
A. To increase electrical conductivity
B. To provide freeze protection
C. To eliminate the need for an expansion tank
D. To prevent solar radiation from reaching the absorber
B. To provide freeze protection
Propylene glycol lowers the freezing point of the heat-transfer fluid,
helping protect collector piping and other components from freezing
damage in climates where temperatures can fall below 32°F (0°C).
6. Why must the concentration of glycol in a solar thermal system be
controlled carefully?
A. Excessive glycol concentration can reduce heat-transfer performance
and increase fluid viscosity
B. Glycol concentration has no effect on system operation
, C. Higher glycol concentration always increases efficiency
D. Glycol concentration determines the collector orientation
A. Excessive glycol concentration can reduce heat-transfer performance
and increase fluid viscosity
Increasing glycol concentration provides greater freeze protection but
also increases viscosity and can reduce heat-transfer efficiency. Proper
concentration must therefore balance freeze protection with pumping
and thermal performance.
7. Which device is normally installed to protect a pressurized solar
thermal system from excessive pressure?
A. Pressure relief valve
B. Check valve only
C. Thermometer
D. Balancing valve
A. Pressure relief valve
A pressure relief valve opens when system pressure reaches its set point,
protecting piping, collectors, storage tanks, and other components from
dangerous overpressure.
8. What is the main function of a check valve in a solar thermal
circulation system?
A. To measure fluid temperature
B. To prevent unwanted reverse flow
