California HVAC C-20 Contractor Exam 2026 – 190 Practice
Questions with Answers & Detailed Rationales, Planning &
Estimating, HVAC Installation, Fabrication, Startup,
Troubleshooting, Maintenance, Repair & Safety
Section 1: Planning and Estimating
Question 1
A residential HVAC system is being designed for a 2,400 sq ft home in Climate Zone 12. The
calculated heating load is 48,000 BTU/h and the cooling load is 36,000 BTU/h. What is the
minimum heating equipment capacity that should be selected?
A. 36,000 BTU/h
B. 42,000 BTU/h
C. 48,000 BTU/h
D. 60,000 BTU/h
Correct Answer: C
Explanation: Equipment must be sized to meet or exceed the calculated load. Undersizing
heating equipment prevents maintaining design indoor temperature during coldest
conditions.¹
Question 2
When performing a Manual J load calculation, which factor has the greatest impact on the
calculated cooling load in a home with west-facing windows?
A. Number of occupants
,B. Window U-factor
C. Solar heat gain through glass
D. Internal lighting wattage
Correct Answer: C
Explanation: West-facing glass experiences peak solar gain during afternoon hours when
outdoor temperatures are highest, significantly driving cooling load calculations.¹
Question 3
A contractor is preparing a bid for a complete HVAC system replacement. The homeowner
asks why a Manual J calculation is necessary when the old system "worked fine." What is the
best response?
A. Manual J is only required for new construction permits.
B. The old system may have been improperly sized, and correct sizing ensures comfort and
efficiency.
C. Manual J is optional for replacements under 5 tons.
D. The calculation is only needed if the ductwork is being replaced.
Correct Answer: B
Explanation: Rule-of-thumb sizing often results in oversized equipment that short-cycles,
fails to control humidity, and wastes energy.¹
Question 4
What does the term "sensible heat" refer to in HVAC load calculations?
,A. Heat that causes a change in moisture content
B. Heat that causes a change in temperature
C. Heat generated by electrical resistance
D. Heat lost through building envelope
Correct Answer: B
Explanation: Sensible heat changes dry-bulb temperature without altering moisture content,
while latent heat changes moisture content without temperature change.¹
Question 5
A duct system is being designed with a total equivalent length of 180 feet and a friction rate
of 0.08 inches W.C. per 100 feet. What is the total static pressure loss due to friction?
A. 0.008 inches W.C.
B. 0.08 inches W.C.
C. 0.144 inches W.C.
D. 1.44 inches W.C.
Correct Answer: C
Explanation: Friction loss equals (friction rate per 100 ft) × (total equivalent length / 100) =
0.08 × 1.8 = 0.144 inches W.C.¹
Question 6
Which of the following best describes the purpose of a psychrometric chart in HVAC design?
, A. To calculate electrical load requirements
B. To determine duct velocity limitations
C. To analyze air properties including temperature, humidity, and enthalpy
D. To size refrigerant lines
Correct Answer: C
Explanation: Psychrometric charts graphically represent thermodynamic properties of moist
air, enabling analysis of heating, cooling, humidification, and dehumidification processes.¹
Question 7
A contractor is estimating the cost for a commercial rooftop unit installation. Which factor is
most likely to cause the largest cost overrun?
A. Minor duct modifications
B. Crane rental for unit placement
C. Discovery of asbestos-containing duct insulation
D. Thermostat replacement
Correct Answer: C
Explanation: Hazardous material abatement requires certified contractors, specialized
procedures, and significant additional costs not typically anticipated in standard estimates.¹
Question 8
Questions with Answers & Detailed Rationales, Planning &
Estimating, HVAC Installation, Fabrication, Startup,
Troubleshooting, Maintenance, Repair & Safety
Section 1: Planning and Estimating
Question 1
A residential HVAC system is being designed for a 2,400 sq ft home in Climate Zone 12. The
calculated heating load is 48,000 BTU/h and the cooling load is 36,000 BTU/h. What is the
minimum heating equipment capacity that should be selected?
A. 36,000 BTU/h
B. 42,000 BTU/h
C. 48,000 BTU/h
D. 60,000 BTU/h
Correct Answer: C
Explanation: Equipment must be sized to meet or exceed the calculated load. Undersizing
heating equipment prevents maintaining design indoor temperature during coldest
conditions.¹
Question 2
When performing a Manual J load calculation, which factor has the greatest impact on the
calculated cooling load in a home with west-facing windows?
A. Number of occupants
,B. Window U-factor
C. Solar heat gain through glass
D. Internal lighting wattage
Correct Answer: C
Explanation: West-facing glass experiences peak solar gain during afternoon hours when
outdoor temperatures are highest, significantly driving cooling load calculations.¹
Question 3
A contractor is preparing a bid for a complete HVAC system replacement. The homeowner
asks why a Manual J calculation is necessary when the old system "worked fine." What is the
best response?
A. Manual J is only required for new construction permits.
B. The old system may have been improperly sized, and correct sizing ensures comfort and
efficiency.
C. Manual J is optional for replacements under 5 tons.
D. The calculation is only needed if the ductwork is being replaced.
Correct Answer: B
Explanation: Rule-of-thumb sizing often results in oversized equipment that short-cycles,
fails to control humidity, and wastes energy.¹
Question 4
What does the term "sensible heat" refer to in HVAC load calculations?
,A. Heat that causes a change in moisture content
B. Heat that causes a change in temperature
C. Heat generated by electrical resistance
D. Heat lost through building envelope
Correct Answer: B
Explanation: Sensible heat changes dry-bulb temperature without altering moisture content,
while latent heat changes moisture content without temperature change.¹
Question 5
A duct system is being designed with a total equivalent length of 180 feet and a friction rate
of 0.08 inches W.C. per 100 feet. What is the total static pressure loss due to friction?
A. 0.008 inches W.C.
B. 0.08 inches W.C.
C. 0.144 inches W.C.
D. 1.44 inches W.C.
Correct Answer: C
Explanation: Friction loss equals (friction rate per 100 ft) × (total equivalent length / 100) =
0.08 × 1.8 = 0.144 inches W.C.¹
Question 6
Which of the following best describes the purpose of a psychrometric chart in HVAC design?
, A. To calculate electrical load requirements
B. To determine duct velocity limitations
C. To analyze air properties including temperature, humidity, and enthalpy
D. To size refrigerant lines
Correct Answer: C
Explanation: Psychrometric charts graphically represent thermodynamic properties of moist
air, enabling analysis of heating, cooling, humidification, and dehumidification processes.¹
Question 7
A contractor is estimating the cost for a commercial rooftop unit installation. Which factor is
most likely to cause the largest cost overrun?
A. Minor duct modifications
B. Crane rental for unit placement
C. Discovery of asbestos-containing duct insulation
D. Thermostat replacement
Correct Answer: C
Explanation: Hazardous material abatement requires certified contractors, specialized
procedures, and significant additional costs not typically anticipated in standard estimates.¹
Question 8
