Cert III Electrician cheat sheet

Hierarchy of control, highest to lowest: eliminate the hazard, substitute, isolate, engineer controls, administrative controls, then PPE; PPE is the last line of defence.

Isolation before work on electrical equipment follows test-before-touch: identify, isolate, lock and tag, prove the tester on a known source, test for dead at all conductors, then re-prove the tester.

Arc flash risk rises with fault current and clearing time; incident energy is expressed in cal/cm² and sets the arc-rated clothing category required.

A safety observer is required for live low-voltage work; the observer must be competent in rescue and resuscitation and must not perform the work.

Residual current devices with a 30 mA rating protect people against earth-leakage shock; the operating time at rated residual current must not exceed 300 ms.

Fire extinguisher selection: CO2 or dry chemical for energised electrical fires; water must never be applied to live electrical equipment.

Approach distances to exposed live low-voltage conductors are governed by state WHS regulations; any work inside the restricted zone requires a risk assessment and permit.

Burns, falls from ladders and manual handling are the most common electrician injuries; ladder use requires a 1-in-4 set ratio and three points of contact.

The model WHS Act imposes a primary duty of care on a person conducting a business or undertaking (PCBU) to ensure health and safety so far as is reasonably practicable.

Officers of a PCBU have a due diligence duty; workers must take reasonable care of themselves and others, follow instructions and report hazards.

PCBUs must consult with workers on WHS matters, and health and safety representatives may issue provisional improvement notices after training.

Notifiable incidents include death, serious injury or illness, and dangerous incidents such as electric shock or plant collapse; the regulator must be notified immediately.

Waste streams: fluorescent tubes and HID lamps contain mercury and are hazardous waste; cable offcuts, copper and drums are recycled separately.

Lead-acid and lithium batteries require separate collection; lithium batteries present fire risk if punctured and must not enter general waste.

Spill response follows contain, absorb, clean up, dispose; absorbent material contaminated with oil or solvent is classified as hazardous waste.

Refrigerant gases are controlled substances under national ozone and greenhouse legislation; only licensed technicians may handle them, and recovery is mandatory.

Ohm's law: V = I × R. Power: P = V × I = I²R = V²/R.

Series circuit: current is common, resistances add, voltage divides in proportion to resistance. Parallel circuit: voltage is common, currents add, reciprocal resistances add.

Kirchhoff's laws: the algebraic sum of currents at a node is zero; the algebraic sum of voltages around a closed loop is zero.

Capacitive reactance Xc = 1/(2πfC) falls with frequency; inductive reactance XL = 2πfL rises with frequency.

Impedance Z = √(R² + (XL − Xc)²); power factor = R/Z = cos φ.

Three-phase star: line voltage = √3 × phase voltage, line current = phase current. Delta: line current = √3 × phase current, line voltage = phase voltage.

RMS value = peak/√2 for a sine wave; average value of a full sine wave is zero, half-cycle average = 0.637 × peak.

A clamp meter reads current by magnetic induction around a single conductor; clamping both active and neutral of a circuit reads zero.

Cable current-carrying capacity is derated by ambient temperature, grouping, thermal insulation and installation method; AS/NZS 3008.1.1 tables give the base and correction factors.

Voltage drop limits in AS/NZS 3000: 5% for consumer mains and 5% from the point of supply to any point of installation for low-voltage installations.

Protective device selection requires In ≥ Ib (design current), In ≤ Iz (cable capacity), and I2 ≤ 1.45 × Iz for the overload condition.

Cable bending radius is typically 8 × overall diameter for fixed thermoplastic-insulated cables; tighter bends damage insulation and conductors.

Cable support spacing for horizontal fixed wiring is generally not more than 300 mm for vertical and 900 mm for horizontal runs, subject to the standard's tables.

Sheath colours: orange for fire-rated cable used in emergency circuits; the active, neutral and earth cores retain standard colours within.

Segregation: communications and data cables must be separated from low-voltage power cables to limit induced noise and maintain insulation integrity.

Underground wiring requires minimum cover depths (typically 500 mm for direct-buried low-voltage cable) and warning tape or marker above the cable.

IP rating: first digit is solids protection 0–6, second digit is liquids protection 0–8; IPX4 is splash-resistant and suits bathrooms.

Switchboards require a main switch, circuit protection, and clear labelling of every circuit; a main switch must be capable of being locked in the off position.

Socket outlets in domestic installations require 30 mA RCD protection; AS/NZS 3000 specifies zones for bathrooms and wet areas.

Lighting efficacy is measured in lumens per watt; LED lamps typically achieve 80–150 lm/W compared with 10–15 lm/W for incandescent.

Lamp colour temperature: 2700–3000 K warm white, 4000 K neutral, 5000–6500 K daylight; colour rendering index above 80 is required for task areas.

Class I equipment relies on protective earthing; Class II is double-insulated and does not require an earth; Class III operates at safety extra-low voltage.

Motor circuits require a disconnecting means, short-circuit protection and overload protection sized to the motor's full-load current and duty.

Luminaire installation must respect manufacturer clearance from thermal insulation; recessed downlights require free air space to dissipate heat.

Synchronous speed Ns = 120 × f / P, where P is the number of poles; induction motors run slightly below synchronous speed at slip.

Slip s = (Ns − Nr)/Ns; typical full-load slip for a standard induction motor is 2–5%.

Direct-on-line starting draws 5–8 times full-load current; star-delta reduces starting current and torque to one third.

A contactor provides frequent switching; an overload relay provides sustained protection; a circuit breaker provides short-circuit protection.

Control circuit symbols: normally open contact closes on energisation; normally closed contact opens; a seal-in (holding) contact maintains the coil circuit after the start button is released.

An emergency stop must be a normally closed, latching, manually reset device wired so that a broken control circuit de-energises the coil.

Single-phasing protection is critical: a three-phase motor running on two phases draws excessive current in the remaining windings and overheats.

Motor direction is reversed by swapping any two of the three supply phases; this can be done with two contactors interlocked mechanically and electrically.

Insulation resistance test at 500 V DC for low-voltage circuits; the minimum acceptable value is 1 MΩ for the installation.

Continuity of protective earthing and equipotential bonding must be verified; the measured resistance must be low enough to operate the protective device within the required disconnection time.

Earth fault loop impedance determines disconnection time; maximum values are tabulated in AS/NZS 3000 for each protective device type and rating.

Polarity testing confirms actives are switched, not neutrals, and that socket outlet wiring is correct at each point.

RCD testing verifies trip time at rated residual current and at half rated current (no trip) and at five times rated current (fast trip).

Fault finding sequence: gather symptoms, form a hypothesis, divide the circuit, test at accessible points, isolate and repair the faulty section, then retest.

Verification includes visual inspection, testing, and issue of a Certificate of Electrical Safety or equivalent compliance document.

Phase rotation must be checked before connecting a three-phase motor to confirm the direction of rotation.

AS/NZS 3000 is the Wiring Rules; it is called up by state and territory electrical safety legislation, and the current edition governs new work.

The Wiring Rules define a MEN (multiple earthed neutral) system: the neutral is earthed at the transformer and at the installation's main earthing point.

Compliance with AS/NZS 3000 is mandatory for electrical installation work; departures require documented equivalent safety justification.

Electrical work must be performed by a licensed electrician, and a Certificate of Compliance must be issued for the work performed.

AS/NZS 3012 covers construction and demolition sites; AS/NZS 3760 covers in-service inspection and testing of electrical equipment.

AS/NZS 4836 sets safe working practice for low-voltage electrical work; AS/NZS 5601 covers gas installations and is not electrical.

Prescribed work, such as consumer mains and metering, requires notification to the supply authority and inspection by the relevant regulator.

A single-line diagram shows the electrical distribution in simplified form: supply, main switchboard, sub-boards, and protective devices.

A wiring schematic shows control circuits with each component drawn in its de-energised state and identified by a reference designator.

A block plan shows the physical layout of equipment and cable routes; a schedule of quantities lists materials and quantities.

Symbols follow AS/NZS 60617; the legend sheet defines all symbols used on the drawing set.

Cable schedules list cable size, type, length, and route; they must match the drawing and the installed installation.

As-built drawings record the final installed configuration and must be updated for every variation and issued to the client at handover.

A specification defines the quality of materials, workmanship, standards and testing requirements; it takes precedence over drawings where conflict exists, subject to the stated order of precedence.

Revision control: the drawing number, revision letter and date identify the current issue; superseded drawings must be withdrawn from site.

Effective handover uses the SBAR structure: situation, background, assessment, recommendation.

A job safety analysis (JSA) is completed before work starts, with the crew consulted and the controls recorded and signed off.

Work orders should record the scope, materials used, hours, and any variations; variations require written approval before proceeding.

Customer communication includes an agreed appointment window, notification of power interruption, and a clear explanation of the fault and the remedy.

Conflict resolution steps: address the issue directly and privately, use neutral language, agree on the outcome, document the agreement.

Toolbox talks are short, documented pre-work briefings covering hazards, controls and the day's tasks.

Time management on site: plan the job, gather materials first, sequence tasks to minimise travel and repeated isolation, and record actual times.

A grid-connected solar PV system uses an inverter to convert DC to AC and must disconnect automatically when the grid is lost (anti-islanding).

PV array sizing: array kWp × peak sun hours × system efficiency gives daily energy in kWh.

Battery energy storage systems require specific installation clearances, ventilation, and fire separation; lithium batteries must be protected from overcharge and thermal runaway.

Power factor correction reduces reactive power and lowers demand charges; capacitors are switched in steps to avoid overcorrection.

Energy efficiency measures: LED lighting, variable speed drives on pumps and fans, power factor correction, and improved insulation.

Heat pump hot water and reverse-cycle air conditioning achieve coefficients of performance of 3–5 compared with resistive heating at 1.

Electric vehicle supply equipment requires dedicated circuit protection, RCD type A or B as specified, and load management to avoid exceeding supply capacity.

Demand response and smart metering allow load shifting; tariffs with time-of-use pricing reward consumption outside peak periods.