Glossary
The terms the calculators and the guides use, each in AmpSize's own words. A term names a clause or a table by number only. No text of a standard is reproduced here.
A
- Adiabatic check
- A fault check that assumes no heat leaves the conductor during the fault. It gives the minimum size from S = √(I²t) / k.
- Fault rating calculatorShort-circuit withstand and the k factor
- AWGAmerican Wire Gage
- The North American system of wire sizes. A smaller gauge number is a larger wire.
- AWG and the NEC for NZ and AU electriciansImperial cable calculator
C
- Cable group
- Circuits that run close enough together to heat one another. AS/NZS 3008.1.1:2025 defines the term, and a grouping factor applies to it.
- GroupingAS/NZS 3008 Table 22 (now 3.33): bunched groupingCable size calculator
- Circuit
- The conductors that one protective device protects, from the switchboard to the load. The AS/NZS 3008.1 grouping tables count circuits.
- Cable size calculatorCurrent-carrying capacity and derating
- Consumer mains
- The conductors between the point of supply and the main switchboard.
- Cable size calculatorPoint of supply
- Correction factorCF, derating factor, rating factor
- A multiplier that adjusts a tabulated rating for a condition that differs from the reference. AS/NZS 3008.1.1:2025 uses this term, where 2017 said derating factor.
- Current-carrying capacity and deratingAS/NZS 3008.1.1:2025: what changed from 2017AS/NZS 3008.1.2:2017 on the standards page
- Current-carrying capacityCCC, current rating
- The current a cable carries continuously before its insulation reaches its temperature limit. It changes with the installation and the site conditions.
- Current-carrying capacity and deratingCable size calculator
D
- d.c.direct current
- Current that flows in one direction only, as from a battery or a PV array. AmpSize writes it as d.c.
- Battery calculatorIEC 60364 and the Wiring Rules
- Diversity
- The allowance for loads that do not all run at full load at the same time. It makes the maximum demand less than the connected load.
- Maximum demand and diversityMaximum demand calculator
E
- ELVextra-low voltage
- A voltage of 50 V a.c. or less, or 120 V ripple-free d.c. or less. AS/NZS 3000:2018 Cl 1.4.128 sets the bands.
- Voltage drop calculator
F
- Final subcircuit
- A circuit that runs from a switchboard to points of use, such as socket-outlets and lights.
- Cable size calculatorCable size for a 32 A single-phase 25 m run
G
- Grouping
- Cables that run close together heat each other, so each one carries less current. A grouping factor applies that reduction.
- Current-carrying capacity and deratingCable size calculator
H
- Harmonics
- Currents at whole multiples of the supply frequency, drawn by electronic loads. Third harmonic currents add together in the neutral of a three-phase circuit.
- Cable size calculator
I
- Ib, In and Iz
- Ib is the design current, In is the device rating and Iz is the cable capacity. A circuit needs Ib ≤ In ≤ Iz.
- Ib, In and Iz
- IEC 60364
- The international series of standards for low voltage installations in buildings. AS/NZS 3000 stays aligned with it.
- IEC 60364 and the Wiring RulesMEN system: multiple earthed neutral explained
- Installation method
- How and where a cable is installed, such as enclosed, unenclosed or buried. It sets the rating column that applies.
- Conduit fill and installation methodsCable size calculator
K
- k factor
- A constant for a conductor and its insulation in the adiabatic check. It depends on the material and the start and final temperatures.
- Short-circuit withstand and the k factorFault rating calculator
M
- Maximum demand
- The highest load that an installation or a circuit is expected to draw. AS/NZS 3000 gives methods to estimate it.
- Maximum demand and diversityMaximum demand calculator
- MEN systemmultiple earthed neutral
- The earthing system of New Zealand and Australia. Neutral and earth join at the main switchboard, so an earth fault returns through the neutral.
- MEN system: multiple earthed neutral explainedTN-C-S
- mV/A·mmillivolts per ampere metre
- The voltage drop of a cable for each ampere and each metre of route. Multiply it by the current and the length to get the drop.
- The mV/A·m methodVoltage drop calculator
P
- Point of supply
- The point where the network conductors meet the consumer mains. AS/NZS 3000 measures voltage drop from this point.
- AS/NZS 3000 Clause 3.6.2: voltage drop limit
- Prospective fault current
- The current that flows in a fault of negligible impedance at a point. The devices and the cables there must withstand it.
- Prospective fault current at a main switchboardFault rating calculator
R
- RCDresidual current device
- A device that switches off when the current that leaks to earth goes above a set value. It protects people against electric shock.
- RCD types and where they are requiredRCD selection calculator
- Reference ambient
- The air or soil temperature that a rating table assumes. NZ uses 30 °C air and 15 °C soil, and AU uses 40 °C and 25 °C.
- AS/NZS 3008.1.1 vs 3008.1.2: AU and NZ conditionsCurrent-carrying capacity and derating
- Route length
- The length of a cable along its path, one way. AS/NZS 3008.1.1:2025 defines the term, and voltage drop and loop impedance grow with it.
- Voltage drop calculatorDC cable size: 48 V battery and 600 V PV arrayMaximum circuit length calculator
S
- Soil thermal resistivity
- How strongly soil resists the flow of heat, in K·m/W. Both parts of AS/NZS 3008.1 assume 1.2 K·m/W.
- AS/NZS 3008 vs BS 7671: cable sizing comparedUnderground cable calculator
T
- TN-C-S
- One conductor does the neutral and protective jobs in part of the system, and separate conductors in the rest. MEN is a TN-C-S system.
- IEC 60364 and the Wiring RulesMEN system: multiple earthed neutral explained
V
- Voltage drop
- The fall in voltage along a cable that carries current. AS/NZS 3000:2018 Cl 3.6.2 limits it to 5 % from the point of supply.
- Voltage drop basicsVoltage drop calculator
- Voltage rise
- The increase in voltage along a cable when an inverter sends current out to the network. It is the opposite of voltage drop.
- Voltage rise calculatorSolar inverter voltage rise at 5 kW
W
- Wiring enclosure
- A conduit, duct or trunking around a cable. A multicore cable in thermal insulation has a lower rating inside one.
- Cable size calculatorConduit fill and installation methods
Z
- Zeexternal earth fault loop impedance
- The part of the earth fault loop impedance that is outside the installation. Zs is Ze plus the impedance of the circuit conductors.
- Loop impedance calculatorZs
- Zsearth fault loop impedance
- The impedance of the path that an earth fault current takes, from the supply and back. A low Zs lets the device clear the fault in time.
- Earth fault loop impedance and disconnection timeLoop impedance calculator