California C-20 HVAC Contractor Course Notes

HIGH-YIELD CLIFF NOTES: This section is about turning building/job data into a defensible design and price. Use Q = U×A×ΔT for simple conduction; Qs = 1.08×CFM×ΔT for standard-air sensible-load questions; ventilation CFM = volume×ACH/60; duct area ft² = CFM/fpm and ×144 for in². Distinguish sensible from latent heat and ventilation from infiltration. Read psychrometric properties correctly. Use Manual J for residential loads, Manual S plus OEM expanded data for equipment selection, and Manual D for residential duct design. For 2025 California residential sizing, indoor design temperatures are 68°F heating and 75°F cooling. Build estimates from direct cost, then apply the stated overhead/profit method; markup and margin are not the same.

• Using 3.41 instead of 1.08 in the sensible-airflow equation.

• Read all four choices before selecting the BEST answer.

HIGH-YIELD CLIFF NOTES: This is the largest C-20 section. Fabricate ducts to the approved design using suitable materials, joints, reinforcement, supports, sealing, and fitting geometry; account for flex-duct compression/sag and fitting losses. Install equipment to applicable code, listing/labeling, approved plans, and manufacturer instructions—never invent a hierarchy to excuse a conflict. Apply V=IR and P=VI, use equipment nameplate ratings, and diagnose low-voltage/control issues from measurements. Refrigerant work requires proper recovery before opening, nitrogen pressure testing (never oxygen), leak testing, evacuation/dehydration, manufacturer charging procedures, and correct piping/insulation. Establish airflow, measure static, balance the distribution system, test safeties and controls, and complete required California Energy Code field-verification/commissioning documentation before acceptance.

• Measuring each cut from the prior cut and accumulating layout error.

• Read all four choices before selecting the BEST answer.

HIGH-YIELD CLIFF NOTES: Diagnose in order: verify complaint/mode, inspect, verify inputs, measure, isolate root cause, repair, and retest. Use sequence-of-operation logic for furnaces and controls. High static/low airflow points toward air-side restriction; one weak branch with normal trunk conditions points local. Correct airflow before judging refrigerant charge; low suction pressure alone is not proof of undercharge. Never bypass safeties. For maintenance, clean/repair the actual defect, use correctly rated parts, restore ducts/insulation/wiring permanently, follow Section 608 for refrigerant circuit work, and document final airflow, electrical, combustion/refrigerant, and safety checks.

• Replacing parts before measuring the failed step.

• Read all four choices before selecting the BEST answer.

HIGH-YIELD CLIFF NOTES: Match PPE to the hazard and replace damaged PPE. Required tight-fitting respirators need a respiratory program, medical evaluation before use/fit test, and fit testing for the exact facepiece model/style/size. Control hazardous energy before service; damaged ladders, cords, and tools come out of service. Cal/OSHA outdoor heat rules require water and shade provisions; shade must be present above 80°F and high-heat procedures apply at 95°F or above, with acclimatization protections. Keep work areas clear and workers out from under suspended loads. HazCom requires a written program, labels, accessible SDSs, and training. Section 608 generally prohibits intentional refrigerant venting; qualifying apprentices must be closely and continuously supervised by an appropriately certified technician. Use regulated dry nitrogen—not oxygen—for refrigeration pressure testing.

• Choosing PPE by habit rather than hazard.

• Read all four choices before selecting the BEST answer.