California C-20 Warm-Air Heating, Ventilating and Air-Conditioning Examination
California C-20 HVAC Contractor Practice Test
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Questions updated at Sep 5, 2026, 10:29 PM CDT
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Today's 10 California C-20 HVAC Contractor questions
Use this California C-20 HVAC Contractor practice test to review California C-20 HVAC Contractor Examination. Questions rotate daily and each answer links back to the source used to write it.
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Question 1 of 10
Objective Official C-20 blueprint: Diagnose HVAC system performance using systematic tests and measurements — Item 128
Troubleshooting, Repair and Maintenance
A technician measures a large temperature difference between the furnace supply plenum and room registers, with ducts routed through an attic. What should be checked?
Temperature loss between plenum and registers can indicate duct heat loss, leakage, or low airflow in unconditioned space.
Concept tested:
Question 2 of 10
Objective Official C-20 blueprint: Calculate component heating and cooling loads — Item 1
Planning and Estimating
A contractor is sizing a replacement system for a bedroom addition. One exterior wall has 240 ft² of area, an overall U-factor of 0.08 Btu/h·ft²·°F, and a 38°F winter design temperature difference. Using Q = U × A × ΔT and ignoring other loads, what is the wall's conductive heat loss?
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Question 3 of 10
Objective Official C-20 blueprint: Calculate labor, material, overhead, and profit in an HVAC estimate — Item 42
Planning and Estimating
For a multi-zone retrofit, four technicians are budgeted for 6 hours each at $75/hour. Equipment costs $7,200 and other materials $1,400. Applying a 14% overhead-and-profit markup, what is the estimated project price before taxes and permits?
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Question 4 of 10
Objective Official C-20 blueprint: Apply Cal/OSHA job-site safety requirements — Item 183
Safety
A portable power tool has a damaged cord with visible conductor insulation. What should be done?
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Question 5 of 10
Objective Official C-20 blueprint: Design duct systems for required airflow and pressure — Item 28
Planning and Estimating
A flex-duct branch is sized correctly on paper but will be installed with deep sag between supports and several compressed bends. What is the best design response?
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Question 6 of 10
Objective Official C-20 blueprint: Maintain and repair HVAC equipment and systems — Item 153
Troubleshooting, Repair and Maintenance
A technician replaces a contactor with a device that fits physically but has lower current and voltage ratings than the original. What should be done?
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Question 7 of 10
Objective Official C-20 blueprint: Apply Cal/OSHA job-site safety requirements — Item 172
Safety
A cord-and-plug condensate pump is being repaired. The technician unplugs it and keeps the plug under exclusive control during the repair. Which safety principle applies?
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Question 8 of 10
Objective Official C-20 blueprint: Calculate component heating and cooling loads — Item 3
Planning and Estimating
A ceiling below a vented attic has 900 ft² of area and an overall U-factor of 0.03 Btu/h·ft²·°F. At the winter design condition, the temperature difference across the ceiling is 40°F. Approximately how many Btu/h are lost by conduction through the ceiling?
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Question 9 of 10
Objective Official C-20 blueprint: Fabricate and assemble duct systems — Item 52
Fabrication, Installation and Startup
A technician is cutting sheet metal for a plenum and repeatedly measures from the previous cut instead of the original reference line. What fabrication risk does this create?
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Question 10 of 10
Objective Official C-20 blueprint: Calculate required supply airflow from sensible load — Item 12
Planning and Estimating
Before selecting branch duct sizes, a contractor converts a 22,032 Btu/h sensible zone load to airflow. With a 24°F supply-to-room temperature difference, what CFM results from Q = 1.08 × CFM × ΔT?
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C-20 California C-20 HVAC Contractor
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Question 1 A technician measures a large temperature difference between the furnace supply plenum and room registers, with ducts routed through an attic. What should be checked?
Answer choices
- A. Gas pressure only, because duct conditions cannot change delivered-air temperature
- B. Duct leakage, insulation condition, and airflow distribution between the plenum and registers
- C. Refrigerant subcooling only, even though the system is in heating mode
- D. Thermostat calibration only, because plenum temperature is always equal to register temperature
Correct answer
Duct leakage, insulation condition, and airflow distribution between the plenum and registers
Temperature loss between plenum and registers can indicate duct heat loss, leakage, or low airflow in unconditioned space.
Wrong-answer review
- A. Gas pressure only, because duct conditions cannot change delivered-air temperature: Incorrect. Duct conditions can materially alter delivered air.
- C. Refrigerant subcooling only, even though the system is in heating mode: Incorrect. Subcooling is not the first diagnostic for a furnace supply-temperature drop.
- D. Thermostat calibration only, because plenum temperature is always equal to register temperature: Incorrect. Thermostat calibration does not explain duct-path temperature loss.
Extra learning features
Why candidates miss this
The distractor “Gas pressure only, because duct conditions cannot change delivered-air temperature” can look plausible because it focuses attention on a familiar number, component, or shortcut rather than the controlling requirement. Follow the symptom through the system sequence and use measurements to isolate the root cause before replacing or adjusting components. On the exam, select the choice that solves the stated problem directly and preserves the required safety, code, design, or measurement logic. Likely wrong answer: Gas pressure only, because duct conditions cannot change delivered-air temperature Review focus: ASHRAE Handbooks
Why this matters
A measured diagnostic process prevents unnecessary parts replacement, identifies unsafe conditions faster, and reduces the chance that a symptom is mistaken for the root cause.
Question 2 A contractor is sizing a replacement system for a bedroom addition. One exterior wall has 240 ft² of area, an overall U-factor of 0.08 Btu/h·ft²·°F, and a 38°F winter design temperature difference. Using Q = U × A × ΔT and ignoring other loads, what is the wall's conductive heat loss?
Answer choices
- A. Approximately 548 Btu/h
- B. Approximately 730 Btu/h
- C. Approximately 912 Btu/h
- D. Approximately 1,095 Btu/h
Correct answer
Approximately 730 Btu/h
Question 3 For a multi-zone retrofit, four technicians are budgeted for 6 hours each at $75/hour. Equipment costs $7,200 and other materials $1,400. Applying a 14% overhead-and-profit markup, what is the estimated project price before taxes and permits?
Answer choices
- A. Approximately $10,670
- B. Approximately $11,856
- C. Approximately $13,042
- D. Approximately $14,227
Correct answer
Approximately $11,856
Question 4 A portable power tool has a damaged cord with visible conductor insulation. What should be done?
Answer choices
- A. Apply electrical tape over the damaged insulation and continue using the tool without restoring the cord's listed integrity.
- B. Continue using the tool through a GFCI because the device is assumed to protect against the damaged cord insulation.
- C. Remove the damaged tool from service until properly repaired or replaced.
- D. Use the tool only in dry areas until the cord can be repaired.
Correct answer
Remove the damaged tool from service until properly repaired or replaced.
Question 5 A flex-duct branch is sized correctly on paper but will be installed with deep sag between supports and several compressed bends. What is the best design response?
Answer choices
- A. Correct the flex-duct layout and support to eliminate excess sag and compression.
- B. Keep the same layout because flex-duct friction is independent of installation condition
- C. Increase register size only, leaving the restrictive flex run unchanged
- D. Add a larger thermostat anticipator to compensate for reduced branch airflow
Correct answer
Correct the flex-duct layout and support to eliminate excess sag and compression.
Question 6 A technician replaces a contactor with a device that fits physically but has lower current and voltage ratings than the original. What should be done?
Answer choices
- A. Keep it because physical fit is more important than electrical rating
- B. Install a larger fuse to protect the undersized contactor
- C. Use a contactor with the required coil and contact ratings.
- D. Lower thermostat temperature so the contactor carries less current
Correct answer
Use a contactor with the required coil and contact ratings.
Question 7 A cord-and-plug condensate pump is being repaired. The technician unplugs it and keeps the plug under exclusive control during the repair. Which safety principle applies?
Answer choices
- A. Exclusive control of an unplugged cord can meet the cord-and-plug exception.
- B. The plug must remain connected because lockout applies only to energized equipment
- C. The technician must energize the pump every few minutes while hands are inside
- D. A thermostat lock is always required even when the unplugged plug is under exclusive control
Correct answer
Exclusive control of an unplugged cord can meet the cord-and-plug exception.
Question 8 A ceiling below a vented attic has 900 ft² of area and an overall U-factor of 0.03 Btu/h·ft²·°F. At the winter design condition, the temperature difference across the ceiling is 40°F. Approximately how many Btu/h are lost by conduction through the ceiling?
Answer choices
- A. Approximately 810 Btu/h
- B. Approximately 1,080 Btu/h
- C. Approximately 1,350 Btu/h
- D. Approximately 1,620 Btu/h
Correct answer
Approximately 1,080 Btu/h
Question 9 A technician is cutting sheet metal for a plenum and repeatedly measures from the previous cut instead of the original reference line. What fabrication risk does this create?
Answer choices
- A. It increases refrigerant pressure because the plenum volume changes
- B. It automatically strengthens each subsequent seam through added overlap
- C. Measurement error can make the finished plenum drift out of tolerance.
- D. It lowers electrical resistance in the blower circuit by reducing metal length
Correct answer
Measurement error can make the finished plenum drift out of tolerance.
Question 10 Before selecting branch duct sizes, a contractor converts a 22,032 Btu/h sensible zone load to airflow. With a 24°F supply-to-room temperature difference, what CFM results from Q = 1.08 × CFM × ΔT?
Answer choices
- A. Approximately 850 CFM
- B. Approximately 700 CFM
- C. Approximately 1,000 CFM
- D. Approximately 1,150 CFM
Correct answer
Approximately 850 CFM
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