CO HVAC Contractor Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which condition most directly causes a furnace heat exchanger to
operate with excessive flue-gas condensation and increased
corrosion risk?
A. Excessively high return-air temperature
B. Excessively low return-air temperature
C. Excessively high supply-air velocity
D. Excessively low blower speed
Answer: B. Excessively low return-air temperature
Excessively low return-air temperature can reduce combustion-product
temperatures below the dew point, allowing acidic condensate to form
on heat-exchanger surfaces and accelerating corrosion.
2. In a forced-air HVAC system, what is the primary purpose of a
return-air system?
A. To increase combustion air
B. To return conditioned air to the air-handling equipment for
recirculation or treatment
,C. To exhaust refrigerant gases
D. To provide outdoor combustion air to the furnace
Answer: B. To return conditioned air to the air-handling equipment for
recirculation or treatment
The return-air system carries air from conditioned spaces back to the
furnace, air handler, or heat pump so that it can be filtered, heated,
cooled, dehumidified, or otherwise conditioned.
3. Which refrigerant property is most important when determining
whether a refrigerant can safely be used with a particular
compressor and system design?
A. Paint color of the equipment
B. Refrigerant pressure-temperature characteristics
C. Length of the electrical conduit
D. Size of the condensate drain
Answer: B. Refrigerant pressure-temperature characteristics
Refrigerant pressure-temperature relationships determine operating
pressures, saturation temperatures, component ratings, and the
appropriate metering and control strategy for the system.
4. What is the principal purpose of superheat measurement at the
evaporator outlet?
A. To determine condenser subcooling
B. To verify that liquid refrigerant is not returning to the compressor
,C. To determine furnace efficiency
D. To measure electrical resistance
Answer: B. To verify that liquid refrigerant is not returning to the
compressor
Superheat indicates how much the refrigerant vapor temperature
exceeds its saturation temperature, helping establish that refrigerant
leaving the evaporator is vapor rather than liquid.
5. What does subcooling primarily indicate in a refrigeration system?
A. The amount of sensible heating in the evaporator
B. The temperature difference between saturated liquid and actual liquid
refrigerant leaving the condenser
C. The amount of air leakage through ductwork
D. The electrical load of the compressor
Answer: B. The temperature difference between saturated liquid and
actual liquid refrigerant leaving the condenser
Subcooling measures how far liquid refrigerant has been cooled below
its saturation temperature and is commonly used to evaluate proper
condenser operation and refrigerant charge.
6. A TXV-controlled refrigeration system has very high evaporator
superheat and normal condenser subcooling. Which condition
should be investigated first?
A. Restricted refrigerant flow through the metering device
B. Excessive condenser airflow
, C. Oversized supply duct
D. Excessive return-air temperature
Answer: A. Restricted refrigerant flow through the metering device
High superheat can occur when insufficient refrigerant enters the
evaporator, and a restricted or improperly operating TXV can produce
this condition.
7. What is the primary purpose of an HVAC equipment disconnecting
means?
A. To increase motor horsepower
B. To provide a means of safely disconnecting equipment from its
electrical supply
C. To control refrigerant pressure
D. To increase airflow
Answer: B. To provide a means of safely disconnecting equipment from
its electrical supply
A disconnecting means allows electrical power to equipment to be
isolated for servicing, maintenance, and emergency purposes.
8. Which component removes moisture from liquid refrigerant before
it reaches a metering device?
A. Accumulator
B. Filter-drier
C. Condenser fan
D. Crankcase heater
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which condition most directly causes a furnace heat exchanger to
operate with excessive flue-gas condensation and increased
corrosion risk?
A. Excessively high return-air temperature
B. Excessively low return-air temperature
C. Excessively high supply-air velocity
D. Excessively low blower speed
Answer: B. Excessively low return-air temperature
Excessively low return-air temperature can reduce combustion-product
temperatures below the dew point, allowing acidic condensate to form
on heat-exchanger surfaces and accelerating corrosion.
2. In a forced-air HVAC system, what is the primary purpose of a
return-air system?
A. To increase combustion air
B. To return conditioned air to the air-handling equipment for
recirculation or treatment
,C. To exhaust refrigerant gases
D. To provide outdoor combustion air to the furnace
Answer: B. To return conditioned air to the air-handling equipment for
recirculation or treatment
The return-air system carries air from conditioned spaces back to the
furnace, air handler, or heat pump so that it can be filtered, heated,
cooled, dehumidified, or otherwise conditioned.
3. Which refrigerant property is most important when determining
whether a refrigerant can safely be used with a particular
compressor and system design?
A. Paint color of the equipment
B. Refrigerant pressure-temperature characteristics
C. Length of the electrical conduit
D. Size of the condensate drain
Answer: B. Refrigerant pressure-temperature characteristics
Refrigerant pressure-temperature relationships determine operating
pressures, saturation temperatures, component ratings, and the
appropriate metering and control strategy for the system.
4. What is the principal purpose of superheat measurement at the
evaporator outlet?
A. To determine condenser subcooling
B. To verify that liquid refrigerant is not returning to the compressor
,C. To determine furnace efficiency
D. To measure electrical resistance
Answer: B. To verify that liquid refrigerant is not returning to the
compressor
Superheat indicates how much the refrigerant vapor temperature
exceeds its saturation temperature, helping establish that refrigerant
leaving the evaporator is vapor rather than liquid.
5. What does subcooling primarily indicate in a refrigeration system?
A. The amount of sensible heating in the evaporator
B. The temperature difference between saturated liquid and actual liquid
refrigerant leaving the condenser
C. The amount of air leakage through ductwork
D. The electrical load of the compressor
Answer: B. The temperature difference between saturated liquid and
actual liquid refrigerant leaving the condenser
Subcooling measures how far liquid refrigerant has been cooled below
its saturation temperature and is commonly used to evaluate proper
condenser operation and refrigerant charge.
6. A TXV-controlled refrigeration system has very high evaporator
superheat and normal condenser subcooling. Which condition
should be investigated first?
A. Restricted refrigerant flow through the metering device
B. Excessive condenser airflow
, C. Oversized supply duct
D. Excessive return-air temperature
Answer: A. Restricted refrigerant flow through the metering device
High superheat can occur when insufficient refrigerant enters the
evaporator, and a restricted or improperly operating TXV can produce
this condition.
7. What is the primary purpose of an HVAC equipment disconnecting
means?
A. To increase motor horsepower
B. To provide a means of safely disconnecting equipment from its
electrical supply
C. To control refrigerant pressure
D. To increase airflow
Answer: B. To provide a means of safely disconnecting equipment from
its electrical supply
A disconnecting means allows electrical power to equipment to be
isolated for servicing, maintenance, and emergency purposes.
8. Which component removes moisture from liquid refrigerant before
it reaches a metering device?
A. Accumulator
B. Filter-drier
C. Condenser fan
D. Crankcase heater
