CA C-20 HVAC study guide
CA C-20 HVAC · Work through your exam, one topic at a time.
The CSLB C-20 Warm-Air Heating, Ventilating and Air-Conditioning Contractor license is the California credential that allows a business to contract for the installation, alteration, and repair of warm-air heating, ventilating, air-conditioning, and refrigeration systems. It is aimed at working technicians and installers who are ready to move into ownership or qualifier roles, and at existing businesses adding a specialty. The CA C-20 HVAC study guide has 9 sections and about 2,626 words.
01Planning, Layout, and Estimating
A C-20 project begins with a room-by-room load calculation (ACCA Manual J or an approved equivalent), never a rule of thumb. Sensible and latent loads are computed separately; equipment is then selected (Manual S) to meet both at design conditions, and the air distribution system (Manual D) must be able to deliver that capacity.
300 words, about 2 min02Ductwork and Sheet Metal Fabrication and Installation
Duct systems are sized by a recognized method, usually equal friction or the static pressure budget. Compute available static pressure (fan total minus drops across coil, filter, grilles, and heat exchanger), divide by total effective length, and you get a friction rate in inches of water per 100 ft.
292 words, about 1 min03Refrigeration Cycle and System Components
The vapor-compression cycle: the compressor raises pressure and temperature, the condenser rejects heat and subcools the liquid, the metering device drops pressure and temperature, and the evaporator absorbs heat, producing superheated vapor. Saturation temperature tracks pressure; a pressure-temperature chart converts one to the other.
284 words, about 1 min04Heating Equipment and Heat Pump Systems
Gas furnace sequence of operation: thermostat calls for heat, the inducer energizes and proves at the pressure switch, ignition (hot surface or spark) lights the burners, the flame is proved by flame rectification, the blower comes on after a delay, and it runs past shutdown on blower-off delay. Safety devices include the high-limit switch, rollout switch, flame sensor, and on condensing units the blocked-vent and condensate switches.
298 words, about 1 min05Electrical Systems, Motors, and Controls
Start with Ohm's law and power relationships for single and three phase, then apply them to actual parts: contactors and relays, heat sequencers, defrost boards, 24 V transformers, thermostats and the common wire, run and start capacitors, and motor overloads. Motor types you must recognize: PSC, ECM constant torque, ECM constant airflow, and three-phase induction.
287 words, about 1 min06Piping, Refrigerant Handling, and Brazing
Refrigerant lines are sized from manufacturer tables using equivalent length, which includes fittings and vertical risers, so that pressure drop and oil return both stay acceptable. Use ACR copper, cut with a tubing cutter, deburr, and keep dry nitrogen flowing through the line while brazing.
301 words, about 2 min07Testing, Evacuation, Charging, and Startup
Order of operations is test, evacuate, charge, start. Pressure-test with dry nitrogen to the manufacturer's limit, often 300 to 550 psig, and hold it.
291 words, about 1 min08Troubleshooting, Maintenance, and Repair
Use a consistent order: verify the complaint, check thermostat settings and power, confirm airflow through filter, blower, belt, and coil, then measure pressures, temperatures, superheat, subcooling, temperature split, static pressures, and amp draw. Most no-cooling calls are air-side problems, such as a loaded filter, dirty evaporator, collapsed flex duct, or closed damper.
281 words, about 1 min09Safety Practices and Code Compliance
The license carries legal and safety obligations. Personal protection first: eye protection and gloves, arc-rated clothing where required, lockout and tagout before electrical work, and awareness that liquid refrigerant causes frostbite and vapor displaces oxygen and decomposes into toxic products near flame.
292 words, about 1 min