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Foundation
16 pages- 28 Sept 2026 · 4 min readConduit fill and installation methods
How the conduit space factor works, what the fill percent means against the 40 % limit, and how the install method names on site map to the 3008 columns.Conduit FillCable Size - 19 Sept 2026 · 5 min readCurrent-carrying capacity and derating
Why one cable size has many ratings. Install method, ambient, grouping, soil and depth, with a 25 A circuit that needs 10 mm² once the factors apply.Cable Size - 9 Oct 2026 · 3 min readDownlights and insulation: IC-4, CA90 and Non‑IC
The six recessed luminaire classes, what insulation may do around each, which a NZ or AU home may have, the default clearances, and the roof space warning sign.Downlight ClearanceCorrection Factors - 8 Oct 2026 · 3 min readHome batteries and AS/NZS 5139
How a home solar battery is sized in kWh, what usable, nominal, depth of discharge and round-trip efficiency mean, and where AS/NZS 5139 lets one go.Home BatteryBatteryDC Cable Size - 13 Oct 2026 · 4 min readHome battery location and clearances
Where AS/NZS 5139 lets an all-in-one home battery go. Restricted places, 600 and 900 mm zones, the habitable room barrier, ceiling, IP codes and working space.Battery Location CheckHome Battery - 7 Oct 2026 · 3 min readHow many circuits can go on one RCD
The AS/NZS 3000 Cl 2.6.2.4 arrangement rules in plain words, which circuits need a 30 mA RCD in NZ and AU homes, how RCBOs count, and why the rules exist.RCD ArrangementRCD Selection - 20 Oct 2026 · 3 min readIP ratings explained: each digit and letter
What the two numerals of an IP code mean, what X, the letters A to D and H, M, S, W add, why IP67 is not better than IP65 for jets, and where 3000 sets a code.IP RatingWet Area Zones - 22 Sept 2026 · 4 min readMEN system: multiple earthed neutral explained
MEN means multiple earthed neutral. In NZ, earth and neutral join at the main switchboard. A fault on a 32 A C curve circuit then draws 343.8 A and clears.Loop ImpedanceCable SizeFault Rating - 28 Oct 2026 · 6 min readOhm's law and power on d.c. and a.c.
Ohm's law and the power formulas on d.c., single‑phase and three‑phase a.c.: how power factor and impedance change them, and how any two values give the rest.Ohm's LawThree Phase PowerFull Load Current - 12 Oct 2026 · 3 min readPower points near a cooktop, gas bottle and sink
The AS/NZS 3000 zones that keep power points, switches and lights away from cooktops, gas cylinders, gas vents and regulators, and where sinks are checked.Accessory LocationWet Area Zones - 22 Oct 2026 · 2 min readSwitchboard labels and circuit charts
What AS/NZS 3000 asks a switchboard to carry: a chart tying each device to what it supplies, MAIN SWITCH, MAIN SWITCHBOARD, solar labels and marked neutrals.Circuit ChartSwitchboard Form - 6 Oct 2026 · 3 min readThe 5 % voltage drop limit from supply to load
What AS/NZS 3000 Cl 3.6.2 limits, how the drop of the mains, submains and final subcircuits adds by percent, the four exceptions and why any split is yours.Total Voltage DropVoltage DropCable Size - 21 Oct 2026 · 2 min readThe order of verification tests
Why AS/NZS 3017 tests earth continuity before insulation and loop impedance before RCDs, which circuits take which test, and where each limit comes from.Test ScheduleTest Results - 19 Sept 2026 · 4 min readVoltage drop basics
Ohm's law on a cable, the mV/A·m shortcut, the percent limit and the maximum length, worked on a 25 A run over 35 m of 4 mm² copper.Voltage DropVoltage RiseCable Size - 6 Oct 2026 · 4 min readWho may do electrical work in NZ
The regulations that govern prescribed electrical work and its certification in New Zealand, named by number, with the paperwork abbreviations explained.Regulatory PathwayMaximum Demand - 19 Oct 2026 · 2 min readWire colours in NZ and Australia, old and new
The active, neutral and earth colours of AS/NZS 3000 Table 3.4, the NZ black neutral, older yellow and green conductors, and flexible cord colours.Conductor ColoursTest and Tag
Working
30 pages- 27 Sept 2026 · 4 min readAS/NZS 3008.1.1:2025: what the AU part covers
What AS/NZS 3008.1.1:2025 covers, a.c. to 0.6/1 kV and d.c. to 1500 V at 40 °C air and 25 °C soil, how its sections run, and where the d.c. tables are.Cable SizeDC Cable Size - 29 Oct 2026 · 5 min readBattery classes and arc flash in AS/NZS 5139
How AS/NZS 5139 classes a battery system by hazard and decisive voltage class, works its arc flash energy, and sets the PPE, consequence and home limits.Battery Arc Flash and ClassHome BatteryArc Flash - 23 Oct 2026 · 4 min readCable tray fill: one layer, tiers and grouping
How cables lie on a tray or ladder for AS/NZS 3008.1, touching or spaced, when a run needs another tier, and why there is no fill percentage to work to.Cable Tray FillCable SizeCorrection Factors - 8 Oct 2026 · 5 min readChecking an existing circuit
The five checks AmpSize runs on an installed circuit, from Iz and voltage drop to Zs and fault withstand, and what a site test adds that a calculation cannot.Circuit CheckCable SizeLoop Impedance - 30 Oct 2026 · 4 min readChoosing a comms cable: length and screen
Check a comms cable run before you order it. Length limits for RS-485 and Ethernet, the 4–20 mA loop and the screen rule, with three worked runs.Comms Cable SelectorLoop Power Budget - 2 Nov 2026 · 6 min readConstruction site supplies: AS/NZS 3012
What AS/NZS 3012:2019 asks of the electrical supply on a construction or demolition site, from the supply and the RCDs to cords, generators and testing.Construction Site SupplySite Cord LengthTest and TagHand-held SupplyShow and Carnival Wiring - 10 Oct 2026 · 4 min readControl panels and PLC wiring
Segregation of LV and ELV in a control panel, terminal and numbering practice, panel earthing, and the 24 V DC voltage drop that long instrument loops fail on.Voltage DropBatteryFull Load CurrentScreen and Drain Earthing - 8 Oct 2026 · 5 min readCorrection factors in the 2017 and 2025 editions
What each AS/NZS 3008 correction factor does, how the factors multiply, and which values changed when AS/NZS 3008.1.1:2025 replaced the 2017 tables.Correction FactorsCable Size - 6 Oct 2026 · 5 min readDamp situations: the Section 6 zones
How AS/NZS 3000 Section 6 zones the space around baths, showers, basins, spas, pools, fountains and saunas, how to read an IP code, and what A2 changed.Wet Area ZonesRCD Selection - 8 Oct 2026 · 5 min readDC voltage drop and conductor resistance
Why d.c. drop is 2 × I × R × L, why it has no reactance or power factor, and how the hot resistance, the cable tables, the limit and parallel cables change it.Voltage DropDC Cable Size - 8 Oct 2026 · 3 min readEarthing an outbuilding: earth or its own MEN
When a shed or sleep-out takes an earth with its submain and when it may have its own MEN link and electrode, the PEN size, and the electrode depths to use.Outbuilding EarthingEarthing and Bonding - 26 Oct 2026 · 5 min readGenerator sizing for motor starting
Why a motor's start, not its running load, often sets a generator's size. Running and starting kVA, voltage dip, starting methods and derating.Generator SizingGenerator CurrentMotor - 19 Sept 2026 · 3 min readIB ≤ IN ≤ IZ: the overload rule on a 32 A circuit
The overload rule is IB ≤ IN ≤ IZ. A grouped 32 A circuit fails on 6 mm² and passes on 10 mm², with an IZ of 37.6 A. Why the order matters.Cable SizeFault RatingLoop Impedance - 27 Sept 2026 · 4 min readIEC 60364 and the Wiring Rules
IEC 60364 is the international series that AS/NZS 3000 stays aligned with. See how its parts are numbered, what TN-C-S, TT and IT mean, and where MEN fits.Loop ImpedanceMaximum DemandCable Size - 2 Nov 2026 · 4 min readLighting layout and the lumen method
How many luminaires does a room need? The lumen method from target lux to a grid, worked on an 8 m by 6 m office, with the checks the tool applies.Lighting Lumen Method - 19 Sept 2026 · 5 min readLoop impedance and disconnection time
Ze, R1+R2, Zs and Ia, and the two disconnection times, worked on a 32 A curve C circuit over 30 m that returns 0.79 Ω against a 0.96 Ω limit.Loop ImpedanceCable Size - 19 Sept 2026 · 4 min readMaximum demand and diversity
Why consumer mains are smaller than the sum of the loads. The four methods of Cl 2.2.2, the Table C1 groups, and a house that lands on 70.18 A.Maximum DemandThree Phase Power - 11 Oct 2026 · 4 min readMotor circuits and starting
How full load current sizes the cable and starting current sizes the device on a motor circuit, with a worked 22 kW 400 V motor and the cable the tool selects.MotorFull Load CurrentCable SizeVoltage Drop - 14 Oct 2026 · 4 min readMotor starters, contactors and overload relays
How to choose a motor starter: locked-rotor current, star-delta, soft starters, AC-3 and AC-23 duty, the overload relay and when motor protection applies.Motor CircuitMotorCable Size - 15 Oct 2026 · 3 min readMotor starting methods: current and torque
Why a cage motor draws six or seven times full load current at start, and how star-delta, an autotransformer, a soft starter and a drive trade it for torque.Motor Starting MethodsMotor - 2 Nov 2026 · 4 min readObtrusive light and the 4282 zones
How AS/NZS 4282 limits spill light from outdoor lighting at a neighbour's window, by environmental zone A0 to A4, curfew, intensity and upward light ratio.Obtrusive Light - 8 Oct 2026 · 4 min readPower factor and reactive power
What power factor is, why a low one costs current and capacity, how a capacitor bank corrects it in steps, and when harmonics call for a detuned bank.Power Factor CorrectionFull Load CurrentThree Phase Power - 15 Oct 2026 · 4 min readPV and inverter basics
How a grid-connected PV system connects to an installation, why voltage rise sets the inverter cable, and which standards the AmpSize tools cannot quote.Voltage RiseCable SizeBatteryMaximum Demand - 16 Oct 2026 · 4 min readPV array isolators and earthing
How parallel strings feed a fault, what Ithe, Ie and make and break mean for a d.c. isolator, and how AS/NZS 5033 earths and alarms a PV array.PV Array Isolator and EarthingPV String SizingDC Cable Size - 16 Oct 2026 · 3 min readPV string voltage and temperature
Why a PV string's voltage rises in the cold and falls in the heat, how AS/NZS 5033 limits it, and how the string current, fuses and isolator follow.PV String SizingDC Cable Size - 27 Oct 2026 · 4 min readRCD leakage and nuisance tripping
Why an RCD trips with no fault. Where standing leakage comes from, the one-third and one-half points of Cl 2.6.2.1, class limits against measured figures.RCD Leakage BudgetRCD ArrangementTest and Tag - 23 Sept 2026 · 5 min readRCD types and where they are required
Type AC, A, F and B, what each one detects, and the clauses that place them. The fault path behind them, worked on a 20 A circuit over 25 m.RCD SelectionLoop Impedance - 24 Sept 2026 · 4 min readShort-circuit withstand and the k factor
The adiabatic check in plain terms: prospective fault current, clearing time and k, worked on 25 mm² copper XLPE at 10 kA for 0.1 s.Fault RatingCable SizeTransformer - 29 Sept 2026 · 4 min readTesting to Section 8: what each test proves
The Section 8 test sequence, what each test shows, and how a calculated earth fault loop impedance compares with the value a tester reads on site.Test ResultsLoop Impedance - 16 Oct 2026 · 4 min readUnderground cables and civil interfaces
Burial categories, depth of cover, bedding and separation for underground cables, with a worked 100 A submain that changes size when the trench changes.Underground CableCable SizeConduit Fill
Advanced
4 pages- 22 Oct 2026 · 4 min readArc flash basics
Arcing current, incident energy, boundary and working distance explained, with three engine runs that show clearing time beating fault current every time.Arc FlashFault RatingIDMT ProtectionTransformer - 5 Oct 2026 · 4 min readHarmonics and neutral sizing
Why third harmonic current adds in the neutral of a four‑wire circuit, what the 0.86 factor does, and how to apply it by hand to a cable size result.Cable SizeThree Phase Power - 19 Sept 2026 · 4 min readIndustrial switchboards: fault rating, form, IP
What the three ratings on an industrial switchboard or motor control centre mean, how each one is chosen, and which AmpSize tools feed the numbers behind them.Fault RatingMotorFull Load Current - 8 Oct 2026 · 3 min readProspective fault current at a board
How the fault current at a board comes from the source impedance and the submain, why the cold cable gives the maximum, and what to compare it with.Fault Level at a BoardFault Rating