Free practice test — 12 questions with full explanations
Original CraftPATH practice questions. These are not real exam questions. Every answer includes the reasoning, why each wrong option fails, the code area it comes from, and the misconception it targets.
Question 1. A fixed-orifice split system shows suction superheat of 30F on a 95F day. The most likely cause is:
Refrigeration Cycle and Charging · Medium · Objective: Interpret superheat.
- A. Overcharge
- B. Undercharge or low airflow across the evaporator (correct)
- C. A failed reversing valve
- D. Oversized condenser
Correct answer: B. Undercharge or low airflow across the evaporator
Why this is right: High superheat means the refrigerant finishes boiling well before the end of the evaporator. On a fixed-orifice system the usual causes are an undercharge or restricted airflow starving the coil of heat.
Why the other options are wrong:
- A. Overcharge — An overcharge drives superheat down, not up, and raises subcooling.
- C. A failed reversing valve — A failed reversing valve produces poor capacity in both modes and abnormal line temperatures, not simply high superheat.
- D. Oversized condenser — Condenser size affects head pressure and subcooling, not evaporator superheat in this pattern.
Where this shows up on the job: Adding refrigerant to a system with a dirty filter and a blocked return is the fastest way to turn a maintenance call into a compressor replacement.
Code reference: Manufacturer charging charts; EPA Section 608 refrigerant handling requirements
Common misconception: Charging to a pressure gauge alone without confirming airflow first.
Question 2. Which measurement is used to charge a system equipped with a thermostatic expansion valve?
Refrigeration Cycle and Charging · Hard · Objective: Charge a TXV system correctly.
- A. Suction superheat
- B. Liquid line subcooling (correct)
- C. Discharge line temperature
- D. Return air wet bulb only
Correct answer: B. Liquid line subcooling
Why this is right: A thermostatic expansion valve meters refrigerant to hold superheat roughly constant, so superheat cannot indicate charge. Charge is set by liquid line subcooling against the manufacturer's target.
Why the other options are wrong:
- A. Suction superheat — Superheat is held by the valve itself, so it does not track charge on a TXV system.
- C. Discharge line temperature — Discharge temperature is a diagnostic for compression and load, not a charging target.
- D. Return air wet bulb only — Wet bulb is an input to the charging chart, not the charging measurement.
Where this shows up on the job: Techs trained only on fixed-orifice equipment routinely overcharge TXV systems by chasing superheat.
Code reference: Manufacturer installation instructions; ACCA charging procedures
Common misconception: Believing one charging method works for every metering device.
Question 3. A residential system delivers 1,200 CFM with a 20F temperature drop across the coil. Approximate sensible capacity is:
Airflow and Duct Design · Medium · Objective: Apply the sensible heat rate relationship.
- A. About 12,960 Btu/h
- B. About 25,920 Btu/h (correct)
- C. About 51,840 Btu/h
- D. About 6,480 Btu/h
Correct answer: B. About 25,920 Btu/h
Why this is right: Sensible heat equals 1.08 times CFM times the temperature difference. 1.08 x 1,200 x 20 equals 25,920 Btu/h.
Why the other options are wrong:
- A. About 12,960 Btu/h — 12,960 uses half the airflow or half the delta-T.
- C. About 51,840 Btu/h — 51,840 doubles the correct result.
- D. About 6,480 Btu/h — 6,480 is a quarter of the correct result.
Where this shows up on the job: This one equation lets you sanity-check delivered capacity on a startup before you ever open a gauge set.
Code reference: ACCA Manual S and standard psychrometric relationships
Common misconception: Using 4.5 (the total-heat constant for enthalpy) in place of 1.08 for sensible heat.
Question 4. On most California residential system changeouts, the energy code requires:
Airflow and Duct Design · Medium · Objective: Apply California duct sealing and testing rules.
- A. No duct testing if the ducts are existing
- B. Duct sealing and a leakage test verified by a third-party HERS rater where applicable (correct)
- C. Only a visual inspection by the installer
- D. Duct replacement in every case
Correct answer: B. Duct sealing and a leakage test verified by a third-party HERS rater where applicable
Why this is right: California's energy standards require duct sealing with verified leakage testing for many alterations and changeouts, and that verification is performed by a certified HERS rater who registers the result.
Why the other options are wrong:
- A. No duct testing if the ducts are existing — Existing ducts are exactly what the alteration requirements target.
- C. Only a visual inspection by the installer — Self-certified visual inspection does not satisfy HERS verification.
- D. Duct replacement in every case — Full replacement is not required; sealing and verified testing is the standard path.
Where this shows up on the job: Skipping HERS registration is one of the most common reasons a California changeout permit cannot be finaled.
Code reference: California Energy Code (Title 24, Part 6) residential alterations and HERS verification provisions
Common misconception: Assuming a like-for-like equipment swap escapes the energy code entirely.
Question 5. A natural-draft 80 percent furnace shows condensation and rust inside the vent connector. The most likely cause is:
Combustion and Venting · Hard · Objective: Diagnose venting problems.
- A. Vent is oversized or too long, letting flue gases cool below dew point (correct)
- B. Gas pressure is too high
- C. The blower is undersized
- D. The thermostat is miscalibrated
Correct answer: A. Vent is oversized or too long, letting flue gases cool below dew point
Why this is right: An oversized or excessively long vent slows flue gas velocity and lets the temperature fall below the dew point, so water condenses in a vent never designed to handle it.
Why the other options are wrong:
- B. Gas pressure is too high — Excess gas pressure raises firing rate and flue temperature rather than causing condensation.
- C. The blower is undersized — Blower sizing affects supply air temperature rise, not vent gas dew point directly in this failure pattern.
- D. The thermostat is miscalibrated — Thermostat calibration changes cycling, not vent temperature profile.
Where this shows up on the job: Orphaned water heaters left on an oversized common vent after a furnace upgrade are the textbook version of this failure.
Code reference: California Mechanical Code venting provisions; appliance venting tables
Common misconception: Treating a bigger vent as inherently safer than a correctly sized one.
Question 6. A gas furnace is installed in a small closet. Combustion air must be provided because:
Combustion and Venting · Medium · Objective: Size combustion air openings.
- A. It improves efficiency ratings
- B. The space does not have enough volume to supply air for combustion, ventilation, and dilution (correct)
- C. It is only needed for electric equipment
- D. It reduces refrigerant charge
Correct answer: B. The space does not have enough volume to supply air for combustion, ventilation, and dilution
Why this is right: A confined space lacks the volume needed to supply combustion air, ventilation, and draft-hood dilution air, so openings to an adequate interior space or to outdoors must be provided and sized to the appliance input.
Why the other options are wrong:
- A. It improves efficiency ratings — Combustion air is a safety requirement, not an efficiency rating input.
- C. It is only needed for electric equipment — Electric equipment does not burn fuel and needs no combustion air.
- D. It reduces refrigerant charge — Combustion air has nothing to do with refrigerant charge.
Where this shows up on the job: Closet installations without proper openings produce spillage and carbon monoxide, and inspectors check opening sizes and locations closely.
Code reference: California Mechanical Code combustion air provisions
Common misconception: Counting a louvered door as adequate without calculating free area.
Question 7. A condensing unit nameplate lists a minimum circuit ampacity of 24.6 A and a maximum overcurrent protection of 40 A. The correct installation is:
Electrical and Controls · Medium · Objective: Interpret motor and circuit protection data.
- A. 10 AWG copper conductors on a 40 A maximum breaker (correct)
- B. 14 AWG copper on a 40 A breaker
- C. 10 AWG copper on a 50 A breaker
- D. Any conductor size as long as the breaker is 40 A
Correct answer: A. 10 AWG copper conductors on a 40 A maximum breaker
Why this is right: Conductors must be sized to at least the minimum circuit ampacity, and the overcurrent device must not exceed the maximum listed on the nameplate. 10 AWG copper covers 24.6 A and a 40 A breaker respects the maximum.
Why the other options are wrong:
- B. 14 AWG copper on a 40 A breaker — 14 AWG cannot carry the required 24.6 A minimum circuit ampacity.
- C. 10 AWG copper on a 50 A breaker — A 50 A breaker exceeds the nameplate maximum overcurrent protection.
- D. Any conductor size as long as the breaker is 40 A — Conductor size is never arbitrary; it is set by the minimum circuit ampacity.
Where this shows up on the job: Nameplate MCA and MOCP mismatches are the most frequent electrical correction on HVAC final inspections.
Code reference: California Electrical Code air conditioning and refrigeration equipment provisions
Common misconception: Sizing the conductor to the breaker instead of to the minimum circuit ampacity.
Question 8. Before replacing a run capacitor, a technician must:
Electrical and Controls · Easy · Objective: Identify safe service practice.
- A. Open the disconnect and discharge the capacitor through a resistor (correct)
- B. Only turn the thermostat off
- C. Only shut the gas valve
- D. Nothing; run capacitors are not energized
Correct answer: A. Open the disconnect and discharge the capacitor through a resistor
Why this is right: A run capacitor stores charge after power is removed. The disconnect is opened and the capacitor is safely discharged, ideally through a resistor, before it is handled.
Why the other options are wrong:
- B. Only turn the thermostat off — A thermostat call is a control signal; line voltage remains present.
- C. Only shut the gas valve — The gas valve has nothing to do with the electrical hazard.
- D. Nothing; run capacitors are not energized — Capacitors absolutely retain a dangerous charge after shutdown.
Where this shows up on the job: Capacitor shock is one of the most common injuries among newer service techs.
Code reference: Manufacturer service literature; OSHA 29 CFR 1910 electrical safe work practices
Common misconception: Assuming that removing the thermostat call de-energizes the unit.
Question 9. A technician servicing a residential split system with refrigerant must hold:
Refrigerant Handling and Environmental · Medium · Objective: Apply EPA Section 608 rules in California work.
- A. No certification for residential work
- B. EPA Section 608 Type II certification for high-pressure appliances (correct)
- C. A Section 609 motor vehicle certification
- D. Only a state contractor license
Correct answer: B. EPA Section 608 Type II certification for high-pressure appliances
Why this is right: Servicing high-pressure appliances such as residential split systems requires EPA Section 608 Type II certification. Universal certification also covers it.
Why the other options are wrong:
- A. No certification for residential work — Federal law requires certification to open a system containing regulated refrigerant.
- C. A Section 609 motor vehicle certification — Section 609 applies to motor vehicle air conditioning.
- D. Only a state contractor license — A CSLB license authorizes contracting, not refrigerant handling under federal rules.
Where this shows up on the job: Distributors verify certification before selling refrigerant, and venting violations carry federal penalties.
Code reference: 40 CFR Part 82, Subpart F (EPA Section 608)
Common misconception: Believing the contractor license substitutes for federal technician certification.
Question 10. Which sequence reflects correct residential design practice?
Load Calculation and Equipment Selection · Hard · Objective: Select equipment from a load calculation.
- A. Match the old equipment's tonnage, then design ducts
- B. Manual J load calculation, then Manual S equipment selection, then Manual D duct design (correct)
- C. Duct design first, then pick equipment to fit
- D. Select equipment by square footage rule of thumb
Correct answer: B. Manual J load calculation, then Manual S equipment selection, then Manual D duct design
Why this is right: The load calculation establishes the actual sensible and latent loads, equipment is then selected to match those loads at design conditions, and the duct system is designed to deliver the required airflow.
Why the other options are wrong:
- A. Match the old equipment's tonnage, then design ducts — Replacing tonnage for tonnage perpetuates whatever sizing error already existed.
- C. Duct design first, then pick equipment to fit — Ducts cannot be sized before the required airflow is known.
- D. Select equipment by square footage rule of thumb — Square-foot rules of thumb routinely oversize systems, hurting comfort and humidity control.
Where this shows up on the job: California permits for changeouts increasingly require a documented load calculation rather than a like-for-like match.
Code reference: ACCA Manual J, Manual S, and Manual D; California Energy Code sizing provisions
Common misconception: Assuming an oversized system simply cools faster with no downside.
Question 11. An applicant for a C-20 license must normally pass:
Law and Business · Medium · Objective: Understand the CSLB two-exam structure for C-20.
- A. Only the trade exam
- B. The Law and Business exam plus the C-20 trade exam (correct)
- C. A federal HVAC exam
- D. A city mechanical exam only
Correct answer: B. The Law and Business exam plus the C-20 trade exam
Why this is right: CSLB applicants generally sit two examinations: the Law and Business exam covering contracting law, safety, employment, and financial management, and the trade exam for the classification applied for.
Why the other options are wrong:
- A. Only the trade exam — The trade exam alone does not complete the requirement for most applicants.
- C. A federal HVAC exam — There is no federal contractor licensing exam; EPA 608 is a technician certification, not a license exam.
- D. A city mechanical exam only — Cities do not administer CSLB licensing examinations.
Where this shows up on the job: Applicants who prepare only for the trade half lose a full retake cycle, often several weeks.
Code reference: CSLB applicant examination information
Common misconception: Assuming field experience waives the Law and Business exam.
Question 12. The C-20 classification covers a contractor who:
Law and Business · Easy · Objective: Recall CSLB scope of a C-20 classification.
- A. Installs and services warm-air heating, ventilating, and air-conditioning systems, including related ducts and controls (correct)
- B. Only installs residential furnaces
- C. Performs any electrical work in a building
- D. Installs plumbing drainage systems
Correct answer: A. Installs and services warm-air heating, ventilating, and air-conditioning systems, including related ducts and controls
Why this is right: C-20 is the Warm-Air Heating, Ventilating and Air-Conditioning classification and covers the installation and service of those systems together with the ducts, vents, and controls that make them work.
Why the other options are wrong:
- B. Only installs residential furnaces — The classification is not limited to furnaces or to residential work.
- C. Performs any electrical work in a building — General electrical work belongs to the C-10 classification.
- D. Installs plumbing drainage systems — Plumbing drainage belongs to C-36.
Where this shows up on the job: Working outside your classification is a citable offense even when the work is technically competent.
Code reference: CSLB contractor license classifications
Common misconception: Treating incidental work in another trade as automatically permitted without checking the incidental-and-supplemental rule.
How to study for the CSLB C-20 HVAC contractor exam
Study Title 24 as its own subject
California's energy code is what separates the C-20 exam from a generic HVAC test. Duct sealing and leakage testing, HERS verification, equipment efficiency minimums, and sizing documentation all come from Title 24, Part 6. Spend dedicated time on the residential alterations requirements, because those govern the changeout work that makes up most California HVAC revenue.
Get fluent with the two constants
Sensible heat equals 1.08 times CFM times temperature difference. Total heat equals 4.5 times CFM times enthalpy difference. Candidates lose easy points by swapping them. Work a dozen problems with each until you pick the right one without thinking about it.
Know charging by metering device
Fixed orifice systems are charged on superheat, thermostatic expansion valve systems on subcooling. Learn what high and low readings of each indicate, and practice reasoning from a pair of readings to a diagnosis rather than memorizing single symptoms.
Do not skip combustion and venting
Venting, combustion air, and draft questions carry real weight and real consequences. Learn how to size combustion air openings for a confined space, how vent category affects material, and why an oversized vent condenses. Orphaned appliance scenarios appear often.
A 30-day plan
Week one: take this practice test cold, then work refrigeration cycle and charging. Week two: airflow, duct design, and the Title 24 alteration requirements. Week three: combustion, venting, electrical nameplate data, and load calculation, then retake this test in quiz mode. Week four: Law and Business exclusively from the CSLB reference book, with two days of mixed review at the end.