California C-10 Electrical Contractor Course Notes

EXAM WEIGHT: about 28% — the largest C-10 domain. Existing systems: verify actual field conditions, service/panel/bus/OCPD ratings, conductor sizes, terminations, available fault-current/interrupting ratings, and usable capacity before pricing modifications. Load evaluation: a nameplate or one utility bill is not proof of spare capacity. Use the applicable CEC load calculation or qualifying maximum-demand method when its conditions are met. Documents: work from the current issued drawings, specifications, schedules, addenda, approved submittals, and equipment data. If documents conflict, flag the conflict and obtain the governing clarification; do not assume a universal precedence rule. Core formulas: V = I×R; P = V×I for basic single-phase problems; balanced 3φ apparent power VA = √3×V(line)×I(line); battery energy Wh = V×Ah. Continuous loads: general sizing pattern = 125% of continuous load + 100% of noncontinuous load before other required adjustments/corrections. General small-conductor trap: 12 AWG copper is normally protected at no more than 20 A unless a specific CEC exception applies. Wet locations: NM/NM-B is not a wet/damp-location wiring method; conductors in wet raceway interiors must have wet-location insulation/listing.

• Using panel nameplate rating or a single bill as proof of spare capacity.

• Prioritize this domain: it is approximately 28% of the official CSLB outline.

EXAM WEIGHT: about 27% — essentially tied with Planning/Estimating. Working space: verify CEC 110.26 width, depth, height, access, and unobstructed use. Width is generally 30 in. or equipment width, whichever is greater; depth depends on voltage-to-ground and the applicable Condition; height is generally 6.5 ft or equipment height, whichever is greater, subject to exceptions. Do not use required working space for storage, and coordinate doors, ducts, cabinets, ceilings, and other trades so final access remains compliant. Raceway bends: generally no more than 360° total between pull points for raceways subject to that rule. Raceway fill: common Chapter 9 percentages are 53% for one conductor, 31% for two, 40% for more than two. Do not apply raceway-fill percentages to panelboards or box fill. Pull/junction boxes: for a straight pull, the common minimum is 8× the trade size of the largest raceway in the direction of pull; angle/U pulls use different rules. Boxes/conduit bodies containing wiring must remain accessible. Coordinate access before hard ceilings, ducts, or finishes close the space. PVC: provide expansion/movement fittings where thermal movement requires them; use the physical-damage-rated raceway/schedule where the CEC requires it.

• Thinking grounding to earth alone clears line-to-case faults.

• Grounding/bonding and raceway/access questions are high-value C-10 study time.

EXAM WEIGHT: about 11%. Final device selection must match rating, location, listing, and required protection: GFCI, AFCI, tamper-resistant, weather-resistant, and in-use covers are common traps. Bathroom/dwelling and outdoor/wet-location receptacle rules are location-specific; read the location before selecting the feature. Boxes at combustible surfaces must meet the CEC flush/setback rule; a faceplate cannot hide a noncompliant setback. Switches and required disconnects must remain readily accessible; fixed cabinets or building features cannot make them unusable. Motor/HVAC equipment: verify voltage, phase, nameplate/markings, disconnect location, conductor/protection data, and manufacturer instructions before connection. Panel directories and equipment labels must be legible, durable, clear, and specific; 'lights/plugs/misc.' is not an adequate circuit directory. Specified terminal torque is applied with an approved means; 'tight by feel' and deliberate overtightening are both wrong.

• Assuming an eave makes an outdoor receptacle a dry-location device.

• Think like a final inspector: device type, location, labeling, enclosure integrity, disconnect, and torque.

EXAM WEIGHT: about 16%. Startup sequence: inspect, verify mechanical/electrical completion, establish safe energization, then measure voltage/phase and test protective/control functions. Normal voltage does not prove a GFCI works—operate the test function and verify trip/reset. 120 V phase-to-neutral and about 208 V phase-to-phase is consistent with a 120/208 V three-phase wye system. Wrong motor rotation after safe startup points to phase sequence; use a phase-rotation instrument and approved correction procedure. Troubleshooting flow: define symptom → make safe → verify source → inspect connections → isolate section → select test → compare expected/measured → repair cause → retest. Moisture-related tripping: after safe isolation, insulation-resistance testing can help identify leakage/insulation degradation; isolate sensitive equipment first when the test could damage it. Underground feeder faults: sectionalize and use appropriate fault-location methods before replacing/excavating the entire run.

• Replacing parts before verifying the source or fault.

• Ask 'what measurement would most directly confirm or eliminate the suspected fault?'

EXAM WEIGHT: about 18%. Cal/OSHA questions reward hazard identification and positive control—not warnings or improvised workarounds. Lockout/tagout: notify affected workers, shut down, identify/isolate all energy sources, apply locks/tags, release or restrain stored energy, verify isolation/de-energization, perform work, then follow controlled restoration procedures. If an isolating device can be locked out, lockout is the default unless the applicable Cal/OSHA rule allows a tagout method that demonstrably provides equivalent protection. Group energy control must preserve protection equivalent to each worker's personal lockout/tagout control. PPE: employer hazard assessment drives selection. Damaged PPE is removed from service. Training covers when/what/how, limitations, care, and retraining when hazards or worker understanding change. Face protection does not automatically replace required primary eye protection; select the complete PPE ensemble for the hazard. Cord-and-plug metal-cased tools require grounding where applicable unless a valid listed/labeled exception such as double insulation applies.

• Using tagout for convenience when a lockable isolating device should be locked out.

• Safety is 18%—larger than Finish Wiring and Startup individually.