Commercial guide
Pag-size ng sub-mains at final circuit, at pagbasa ng maximum demand ayon sa AS/NZS 3000 Table C2.
- 5 min basahinBuilder's pole: supply, RCDs and cord lengthsA builder's pole for a house build, worked to AS/NZS 3012:2019. The supply it may take, the 30 mA RCDs, the Table 1 cord lengths and the test intervals.
- 4 min basahinCar-park floodlight: obtrusive light at a boundaryTwo 10 000 lm floodlights 10 m from a neighbour's window in zone A2, checked against AS/NZS 4282 for lux at the window, candela and the upward light ratio.
- 3 min basahinCommercial kitchen kW to amps full load currentTurning a 30 kW commercial kitchen nameplate load into 45.58 A at 400 V three phase, with the power factor step that a plain kW to amps sum leaves out.
- 3 min basahinLighting circuit loop impedance, B curve 10 AA 60 m shop lighting circuit on 1.5 mm² cable with a B curve 10 A device, showing Zs, the maximum Zs, the fault current and the longest run that passes.
- 5 min basahinCable tray fill for a plant room: a second tierLay ten multicore cables on a 300 mm perforated tray in one layer, see when it takes a second tier, and carry the grouping factor into the cable size.
- 4 min basahinSwitchboard fault rating at 25 kA for 1 sA 1 second withstand check at 25 kA on 185 mm² copper XLPE, returning a 174.83 mm² minimum size and a 26.46 kA withstand, with a thin margin explained.
- 3 min basahinGenerator full load current: 200 kVA to ampsA 200 kVA 400 V standby set converted to 288.68 A of full load current, 160 kW of real power and 2,405.63 A of initial fault current from 12 percent reactance.
- 3 min basahinOffice maximum demand per phase with Table C2An office fitout load schedule assessed against AS/NZS 3000 Table C2, group by group, landing on 413.7 A across three phases and 137.9 A per phase.
- 1 min basahinHow far can 4 mm² run on a 25 A circuit?4 mm² copper on a 25 A curve C circuit can run 41 m at full load before it reaches the 5 % voltage drop limit. At 20 A of load it can run 51.25 m.
- 1 min basahinHow many amps can 10 mm² cable carry?10 mm² copper multicore PVC cable carries 50 A enclosed in air at 30 °C in NZ, so a 50 A breaker protects it. Clipped direct, it carries 58 A.
- 1 min basahinHow many amps can 16 mm² cable carry?16 mm² copper multicore PVC cable carries 66 A enclosed in air at 30 °C in NZ, so it takes a 63 A breaker. Grouped with two circuits, it carries 46.2 A.
- 1 min basahinHow many amps can 6 mm² cable carry?6 mm² copper multicore PVC cable carries 38 A enclosed in air at 30 °C in NZ, so it takes a 32 A breaker. At 40 °C it carries 33.44 A.
- 1 min basahinHow many 2.5 mm² cables fit in 20 mm conduit?Six single-core 2.5 mm² cables fit in 20 mm conduit at 34.56 % fill, inside the 40 % limit of AS/NZS 3000 Appendix C. A seventh takes it to 40.32 %.
- 1 min basahinMaximum Zs for a 16 A curve C breakerAS/NZS 3000 Table 8.1 allows a maximum Zs of 1.92 Ω for a 16 A curve C breaker at 230 V. A 30 m run of 2.5 mm² cable reads 0.89 Ω.
- 1 min basahinVoltage drop on 2.5 mm² over 30 m20 A on 2.5 mm² copper over 30 m drops 10.81 V, which is 4.7 % at 230 V and close to the 5 % limit. The run can reach 31.91 m.
- 1 min basahinWhat size cable for a 22 kW EV charger?A 22 kW three-phase EV charger on a 32 A circuit takes 6 mm² copper over 20 m, with 38 A of derated capacity and a 1.04 % drop. At 60 m it takes 10 mm².
- 1 min basahinWhat size cable for a 25 A circuit?A 25 A single-phase circuit takes 4 mm² copper on a typical NZ route, with 29 A of derated capacity. 2.5 mm² stops at 23 A, short of the breaker.
- 3 min basahinSubmain voltage drop estimate for a 160 A tenderA price stage check on a 160 A submain over 80 m on 70 mm² XLPE. See the mV/A·m figure, the 1.89 percent drop and the length the budget allows.
- 3 min basahinSubmain cable size for 3‑phase 100 A over 60 mA 100 A tenancy submain on tray over 60 m at 40 °C. See the derating chain, the four checks and why the loop impedance check sets the size at 70 mm².
- 3 min basahinThree‑phase power: kVA to amps at 400 VThe root three relation between amps, kVA and kW on a 400 V board, worked at 50 A and a 0.9 power factor, with the kvar figure the engine returns.
- 3 min basahinFactory power factor correction: 250 kW at 0.78A 250 kW factory load at 0.78 power factor lifted to 0.95. The kvar, the capacitor steps, the current saved, the kVA released and why the bank is detuned.
- 3 min basahinFault level at a sub‑board, 300 kVA transformerWork the prospective fault current at a sub-board 45 m from a 300 kVA transformer, three-phase and phase-earth, and check 6 kA and 10 kA breakers against it.
- 5 min basahinThree circuits in a hot ceiling: correction factorThree 32 A circuits in conduit across a 40 °C and a 50 °C ceiling space, worked with the NZ 2017 tables and again with AS/NZS 3008.1.1:2025.
- 5 min basahinWhat size breaker for 4 mm² cable4 mm² copper enclosed in air takes a 25 A breaker, and 32 A fails at an Iz of 29 A. Grouping, a hot ceiling, insulation and a long run lower it.
- 3 min basahin22 kW EV charger amps at 400 V three‑phaseA 22 kW three-phase EV charger draws 31.75 A at 400 V. See the inputs, the clause, the arithmetic and the current that feeds cable sizing and demand.
- 3 min basahinGenerator sizing for a 150 kVA holiday parkA 150 kVA three-phase standby set at 400 V gives 216.51 A full load current, 120 kW real power and 1443.38 A fault current from one nameplate.
- 4 min basahinElectrical estimating calculators NZ roundupA roundup of the calculators a New Zealand estimator uses at price stage, with a Table C2 fitout worked through to a demand of 102.95 A per phase.
- 4 min basahinCable size for a 20 A heat pump circuit in summerA 20 A heat pump circuit over 18 m in a 40 °C roof space needs 4 mm², with a derated capacity of 22.88 A and a voltage drop of 1.59 percent.
- 4 min basahinAmpSize vs jCalc vs free cable sizing toolsCompare AmpSize with jCalc and other free cable sizing tools. One 63 A three-phase submain shows which checks decide a size, and what AmpSize leaves out.
- 4 min basahinAS/NZS 3000 Appendix C: conduit space factorWhat the conduit space factor in AS/NZS 3000 Appendix C governs, which tool reads it, and a worked 50 mm conduit that reaches 52.95 % fill against a 40 % limit.
- 4 min basahinAS/NZS 3008.1.2 Table 52: the k factorWhat Table 52 governs, how the adiabatic check uses k, and a 10 kA fault cleared in 0.1 s that needs 22.11 mm² against an installed 25 mm² conductor.
- 3 min basahinAS/NZS 3000 Tables C1 and C2: demand groupsWhat the demand group letters govern, when to use Table C1 or Table C2, and a commercial assessment that returns 276.26 A total and 92.09 A per phase.
- 4 min basahinAS/NZS 3008.1.2 Tables 22 to 29: deratingWhat the derating tables govern, how ambient and grouping combine into one factor, and a 63 A feeder whose capacity falls to 78.85 A on 35 mm² copper.
- 6 min basahinAS/NZS 3008.1.1 table numbers: 2017 to 2025Each AS/NZS 3008.1.1 table AmpSize reads, with its 2017 number, its 2025 number and whether its values moved, and one submain that cites both sets.
- 4 min basahinAS/NZS 3008.1.1 vs 3008.1.2: AU and NZ conditionsThe AU part of AS/NZS 3008.1 rates cable at 40 °C air and the NZ part at 30 °C. One 32 A circuit needs 6 mm² in Australia and 4 mm² in New Zealand.
- 4 min basahinAS/NZS 3008.1.2 Tables 4 to 21: current ratingsWhat the current rating tables govern, which table AmpSize reads today, and a 40 A circuit that lands on 10 mm² with a derated capacity of 50 A.
- 4 min basahinAS/NZS 3008 Table 13 (now 3.18): multicore ratingsWhat AS/NZS 3008 Table 13 gives, why the 2025 AU part calls it Table 3.18, how to read its columns into the calculator, and what moved for buried cable.
- 3 min basahinAS/NZS 3008 Table 22 (now 3.33): bunched groupingAS/NZS 3008 Table 22 is the grouping table for bunched circuits, not a temperature table. The 2025 AU part calls it Table 3.33. Read it in the calculator.
- 3 min basahinAS/NZS 3008 Table 27 (now 3.44, 3.45): temperatureAS/NZS 3008 Table 27 corrects a cable rating for the air or soil temperature. The 2025 AU part splits it into Tables 3.44 and 3.45 and re-derives the factors.
- 5 min basahinAS/NZS 3008 vs BS 7671: cable sizing comparedHow BS 7671 and AS/NZS 3000 with AS/NZS 3008.1 size a cable, where they differ, and why a BS current rating never converts into an AS/NZS one.
- 4 min basahinAWG and the NEC for NZ and AU electriciansAWG sizes and the NEC set against AS/NZS 3000 and 3008.1. A gauge converts to mm², but its rating does not, and the NEC 3 % drop figure is only a note.
- 3 min basahinConduit fill: 4 x 6 mm² singles in 25 mmFour 6 mm² single-core cables in 25 mm conduit, with the fill percent, the space factor and the smallest conduit the tool recommends for the bundle.
- 3 min basahinCommercial maximum demand with Table C2A tender-stage demand assessment for a commercial building using AS/NZS 3000 Table C2, with each group demand and the per-phase figure the tool returns.
- 3 min basahinProspective fault current at a main switchboardA 16 kA fault cleared in 0.1 s on 70 mm² copper XLPE, with the minimum conductor size, the withstand current and the k factor the adiabatic check returns.
- 3 min basahinAS/NZS 3000 Table 8.1: max Zs by curve and ratingTable 8.1 max Zs for a 16 A device, by curve. B allows 3.59 Ω, C allows 1.92 Ω and D allows 1.15 Ω. See why, with a 30 m circuit at 0.89 Ω.
- 5 min basahinAS/NZS 3008.1.1:2025: what changed from 2017The 2025 AU part adds d.c. ratings to 1500 V, renumbers every table and moves some ratings. Four circuits, each run on both editions, show what moves.
- 3 min basahinAS/NZS 3000 Clause 3.6.2: voltage drop limitWhat Clause 3.6.2 governs, how the 5 percent budget splits across mains and subcircuits, and a 25 A run over 35 m that returns 2.6 percent from the engine.
- 4 min basahinCable size for a 32 A single‑phase 25 m runWork through a 32 A single-phase circuit over 25 metres in New Zealand. See every derating factor, the check that sets the size, and the result the tool gives.
- 4 min basahinEarth fault loop impedance and maximum ZsWhat earth fault loop impedance measures, how the maximum Zs check works, and a 32 A circuit on 6 mm² over 25 m that lands on 0.67 ohms against a 0.96 limit.
- 3 min basahinVoltage drop with the mV/A·m methodHow the millivolt per amp metre method works, with a 32 A run over 25 metres on 6 mm² copper and the exact drop, percent and maximum length the tool returns.
Mga calculator na ginagamit ng mga guide na ito
- Site cord length calculatorAng pinakamahabang run ng cord o cable na puwede sa construction site.
- Obtrusive light checkerTingnan ang outdoor light sa boundary window ayon sa AS/NZS 4282.
- Full load current calculatorKalkulahin ang full load current mula sa power, voltage at phase.
- Earth fault loop impedance calculatorTingnan ang earth fault loop impedance laban sa maximum Zs.
- Cable tray at ladder fillLapad ng tray o ladder, mga tier, kg/m at ang grouping factor.
- Cable fault rating calculatorTingnan kung kayang tiisin ng conductor ang fault current.
- Generator current calculatorFull load at fault current ng generator mula sa kVA nito.
- Maximum demand calculatorI-estimate ang maximum demand para sa domestic o non‑domestic loads.
- Maximum circuit length calculatorPinakamahabang run na pinapayagan ng voltage drop at ng fault loop.
- Pagsusuri ng umiiral na circuitTingnan ang naka-install na circuit: cable, device, drop at Zs.
- Conduit fill calculatorTingnan kung kasya ang cable bundle sa conduit.
- Voltage drop calculatorKalkulahin ang voltage drop sa cable run at tingnan ang limit.
- Cable size calculatorHanapin ang pinakamaliit na cable size na pumapasa sa bawat check.
- Three phase power calculatorI-convert sa pagitan ng power, current, voltage at power factor.
- Power factor correction calculatorHanapin ang capacitor kvar para itaas ang power factor.
- Fault level calculatorProspective fault current sa board mula sa source nito.
- Correction factor calculatorBasahin ang bawat correction factor at ang rating na kailangan ng cable.
- Imperial cable size converterHanapin ang device rating para sa lumang imperial cable.