Free practice for the California C-20 warm-air heating, ventilating and air-conditioning contractor exam (CSLB, PSI) — planning, installation, troubleshooting and safety, with a written explanation on every answer.
The C-20 is California's warm-air heating, ventilating and air-conditioning contractor license classification, and its trade exam is given for the CSLB by PSI: closed book, multiple choice, four answer choices per question, 3.5 hours. The official study guide splits it into four sections — planning and estimating, fabrication, installation and startup, troubleshooting, repair and maintenance, and safety — with fabrication and installation alone worth 38 percent of the questions. Practice it below: free, no sign-up, with a written explanation on every question.
No account needed. Pick an answer to see whether it's right and read the explanation — the same explanations you get on every question in the full course.
Every question tells you why the correct answer is correct and defines the terms it uses — so you learn the rule, not just the answer.
Questions are written from scratch against the official codes and agency publications for this exam — never copied from the real exam.
Every question and explanation is fully translated, with the English exam term kept alongside — not a shallow machine translation.
LICENA is a practice tool, not a school. We don't promise a pass — we help you understand the material and walk in prepared.
The full C-20 course is 500 questions across 5 blocks, built on these four sections of the official CSLB C-20 study guide.
Twenty-two percent of the exam, and it is design plus arithmetic: sizing equipment from a load calculation, working psychrometric problems, laying out duct runs, and pricing the job. California stacks its own rules on top of the trade math. A residential heating load has to be calculated at a 68°F indoor design temperature under the Energy Code, and a split-system air conditioner installed here has to meet the Southwest region's SEER2 14.3 minimum rather than the 13.4 national floor. The trap in this section is the rule of thumb — sizing by square footage instead of by a real Manual J load calculation gives you the wrong answer on the exam and an oversized, short-cycling system in the field.
At 38 percent this is the largest section by a wide margin, and it is where most candidates win or lose. It spans duct fabrication, equipment installation, electrical and mechanical components, plumbing and refrigeration components, air distribution, and system startup. Expect the California duct rules in detail: R-6 minimum insulation on supply and return ducts in unconditioned space, and no cloth-backed rubber-adhesive duct tape as a sealing method unless it is used together with mastic and draw bands. Expect electrical questions too — the disconnecting means for a condensing unit belongs within sight of the unit, not behind a panel you have to pull to reach the equipment. If the electrical side is where you feel thin, the C-10 Electrical practice test drills the same code logic from the other direction.
Twenty percent, and it rewards diagnostic reasoning rather than recall: reading pressures and temperatures, isolating a failed component, and knowing what the law allows while you work. Refrigerant handling turns up constantly here. A high-pressure system holding under 200 pounds of charge only has to come down to atmospheric pressure — zero inches of mercury vacuum — before it is opened, but knowingly venting refrigerant is prohibited outright and recovery equipment has to be certified. Watch the questions that describe a symptom and ask for the most likely cause: more than one option will be a genuine fault, and only one fits the exact conditions named in the stem, so read the stem twice before you look at the answers.
Twenty percent, split between personal protective equipment, Cal/OSHA jobsite requirements, and handling hazardous materials. California is stricter than federal OSHA in places, and the exam knows it: fall protection is triggered above seven and a half feet, not the federal six, and shade must be present once the work-area temperature passes 80°F. Refrigerant, refrigerant oil, and any asbestos-containing material you disturb around old ductwork all fall under hazardous handling. If refrigerant rules are your weak spot, the EPA 608 practice test covers that side in far more depth.
You take the C-20 on a computer at a PSI testing center, closed book, with four answer choices per question and 3.5 hours for the exam. Some questions require mathematical computation and a calculator is provided; there is no penalty for guessing, so nothing should be left blank. Results are pass or fail on the spot, and a failing report breaks your score down by section so you can see exactly where you lost it. You may retake after 21 calendar days, paying a re-examination fee to PSI, as long as you are still inside your application's 18-month window. Read the official CSLB C-20 study guide before you book — it lists the sections, the weights and the reference books. One thing worth knowing early: CSLB publishes official Spanish versions of ten exams and C-20 is not one of them, so for the C-20 you either test in English or request an approved translator through CSLB.
The LICENA C-20 course is 500 questions across five blocks. At 30 a day that is roughly three weeks — one full pass, then a second pass over everything you missed. Weight your time the way the exam weights itself: most of it belongs in fabrication, installation and startup, because 38 percent of the questions live there. Read the explanation on every question you get wrong, and on the ones you guessed right too; the exam rewords facts, so remembering that duct insulation is R-6 matters far less than knowing which rule that number comes from and what the exceptions are. Everyone applying also sits the CSLB Law & Business exam, so plan for two exams rather than one. And treat any prep service promising a guaranteed pass as a warning sign — nobody honest can promise that.
The full 500-question C-20 bank with a written explanation on every answer, weak-area practice and a timed final exam, in EN·ES·RU. California exam-prep schools list programs from about $250 to $1,200 — this is $20/month, on your phone, cancel anytime.
Create free account The free sample above stays free. Creating an account is free — no card needed.LICENA gives you practice questions to study with. We are not an accredited school and we do not guarantee that you will pass any exam.
LICENA provides online practice only. Registration, exam scheduling and licensing are handled by the CSLB and its exam vendor PSI — not by LICENA. LICENA is not affiliated with the CSLB or PSI.