CO HVAC Contractor Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A Colorado HVAC contractor is preparing to install a new gas-fired
forced-air furnace in a residential building. Before selecting the
furnace, which factor is most important for determining the
required heating capacity?
A. The electrical service rating only
B. The number of supply registers regardless of building characteristics
C. A properly calculated building heating load based on the structure's
envelope, climate, infiltration, and internal conditions
D. The furnace capacity of the previous heating system
Answer: C
The heating capacity should be based on a calculated heat loss rather
than the size of the existing equipment. Load calculations account for
insulation, windows, infiltration, outdoor design temperature, and other
factors that determine actual heating demand.
2. A contractor is sizing a central air-conditioning system for a
Colorado residence. The calculated cooling load is 36,000 Btu/h.
, Which nominal equipment size most closely corresponds to this
calculated load?
A. 1.5 tons
B. 2 tons
C. 3 tons
D. 5 tons
Answer: C
One ton of refrigeration is nominally equal to 12,000 Btu/h. Therefore,
36,000 Btu/h corresponds to approximately 3 tons of cooling capacity.
3. An HVAC contractor discovers that a furnace has a cracked heat
exchanger. What is the primary safety concern associated with
operating the furnace in this condition?
A. Excessive refrigerant pressure
B. Carbon monoxide entering the occupied space
C. Increased domestic water pressure
D. Reduced electrical grounding
Answer: B
A cracked heat exchanger can allow combustion products, including
carbon monoxide, to enter the air stream and potentially be distributed
throughout the occupied space. The furnace should not be operated
until the unsafe condition is corrected.
4. A natural-gas furnace is installed in a mechanical room. Which
condition is essential for safe combustion?
,A. The room must always be maintained below 40°F
B. The furnace must receive adequate combustion and dilution air when
required by its design
C. The furnace must share its flue with a clothes dryer
D. The furnace must have a return-air grille directly above the burner
Answer: B
Fuel-burning appliances require adequate air for combustion and safe
operation unless they are specifically designed as sealed-combustion or
direct-vent appliances. Insufficient combustion air can cause incomplete
combustion and unsafe operation.
5. During commissioning of a gas furnace, the contractor measures
manifold gas pressure. What is the purpose of this measurement?
A. To determine the static pressure of the duct system
B. To verify that the burner is receiving gas at the pressure specified by
the manufacturer
C. To determine the refrigerant charge
D. To measure the furnace's electrical resistance
Answer: B
Manifold pressure affects burner input and combustion performance. It
must be checked against the manufacturer's specified value to ensure
proper and safe furnace operation.
6. A forced-air HVAC system has a return-air filter that is heavily
clogged. Which condition is most likely to result?
, A. Increased airflow and reduced blower load
B. Reduced airflow and potentially increased equipment stress
C. Increased refrigerant volume
D. Higher combustion-air availability
Answer: B
A restricted filter increases resistance on the return side of the system,
reducing airflow. This can increase blower operating stress and cause
heating or cooling equipment to operate outside its intended conditions.
7. An HVAC contractor is evaluating excessive static pressure in a
residential duct system. Which instrument is most appropriate for
measuring duct static pressure?
A. Manometer
B. Hygrometer
C. Tachometer
D. Thermocouple only
Answer: A
A manometer or digital differential-pressure instrument is commonly
used to measure static pressure in HVAC duct systems. Static-pressure
measurements help identify airflow restrictions and duct-system
problems.
8. A furnace has a temperature rise specification of 35°F to 65°F. The
contractor measures a 75°F temperature rise during operation.
What is the most appropriate conclusion?
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A Colorado HVAC contractor is preparing to install a new gas-fired
forced-air furnace in a residential building. Before selecting the
furnace, which factor is most important for determining the
required heating capacity?
A. The electrical service rating only
B. The number of supply registers regardless of building characteristics
C. A properly calculated building heating load based on the structure's
envelope, climate, infiltration, and internal conditions
D. The furnace capacity of the previous heating system
Answer: C
The heating capacity should be based on a calculated heat loss rather
than the size of the existing equipment. Load calculations account for
insulation, windows, infiltration, outdoor design temperature, and other
factors that determine actual heating demand.
2. A contractor is sizing a central air-conditioning system for a
Colorado residence. The calculated cooling load is 36,000 Btu/h.
, Which nominal equipment size most closely corresponds to this
calculated load?
A. 1.5 tons
B. 2 tons
C. 3 tons
D. 5 tons
Answer: C
One ton of refrigeration is nominally equal to 12,000 Btu/h. Therefore,
36,000 Btu/h corresponds to approximately 3 tons of cooling capacity.
3. An HVAC contractor discovers that a furnace has a cracked heat
exchanger. What is the primary safety concern associated with
operating the furnace in this condition?
A. Excessive refrigerant pressure
B. Carbon monoxide entering the occupied space
C. Increased domestic water pressure
D. Reduced electrical grounding
Answer: B
A cracked heat exchanger can allow combustion products, including
carbon monoxide, to enter the air stream and potentially be distributed
throughout the occupied space. The furnace should not be operated
until the unsafe condition is corrected.
4. A natural-gas furnace is installed in a mechanical room. Which
condition is essential for safe combustion?
,A. The room must always be maintained below 40°F
B. The furnace must receive adequate combustion and dilution air when
required by its design
C. The furnace must share its flue with a clothes dryer
D. The furnace must have a return-air grille directly above the burner
Answer: B
Fuel-burning appliances require adequate air for combustion and safe
operation unless they are specifically designed as sealed-combustion or
direct-vent appliances. Insufficient combustion air can cause incomplete
combustion and unsafe operation.
5. During commissioning of a gas furnace, the contractor measures
manifold gas pressure. What is the purpose of this measurement?
A. To determine the static pressure of the duct system
B. To verify that the burner is receiving gas at the pressure specified by
the manufacturer
C. To determine the refrigerant charge
D. To measure the furnace's electrical resistance
Answer: B
Manifold pressure affects burner input and combustion performance. It
must be checked against the manufacturer's specified value to ensure
proper and safe furnace operation.
6. A forced-air HVAC system has a return-air filter that is heavily
clogged. Which condition is most likely to result?
, A. Increased airflow and reduced blower load
B. Reduced airflow and potentially increased equipment stress
C. Increased refrigerant volume
D. Higher combustion-air availability
Answer: B
A restricted filter increases resistance on the return side of the system,
reducing airflow. This can increase blower operating stress and cause
heating or cooling equipment to operate outside its intended conditions.
7. An HVAC contractor is evaluating excessive static pressure in a
residential duct system. Which instrument is most appropriate for
measuring duct static pressure?
A. Manometer
B. Hygrometer
C. Tachometer
D. Thermocouple only
Answer: A
A manometer or digital differential-pressure instrument is commonly
used to measure static pressure in HVAC duct systems. Static-pressure
measurements help identify airflow restrictions and duct-system
problems.
8. A furnace has a temperature rise specification of 35°F to 65°F. The
contractor measures a 75°F temperature rise during operation.
What is the most appropriate conclusion?
