Arotake ara iahiko o nāianei
Tirohia tētahi ara iahiko kua whakatūria: te taura, te taputapu, te heke me te Zs.
Reads AS/NZS 3008.1.2:2017 (NZ), AS/NZS 3008.1.1:2017 and 2025 (AU) and AS/NZS 3000:2018. Tables checked 27 Sept 2026.
Whakamātau mahi 7
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- Check the breaker on a 4 mm² circuitWhether a 32 A breaker suits 4 mm² cable, and the largest breaker the cable allows.
- Check an existing three‑phase submainWhether 16 mm² on a 63 A breaker over 80 m passes the cable, drop and Zs checks.
- Check a 20 A breaker on 2.5 mm²Whether a 20 A breaker suits a 2.5 mm² circuit.
- Check a 32 A breaker on 6 mm²Whether a 32 A breaker suits a 6 mm² circuit.
- Check a 16 A breaker on 1.5 mm²Whether a 16 A breaker suits a 1.5 mm² circuit.
- Check a 63 A breaker on 16 mm²Whether a 63 A breaker suits 16 mm² mains.
- Check a 10 A breaker on 1 mm²Whether a 10 A breaker suits a 1 mm² lighting circuit.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Ngā wāhanga
- Wāhanga kotahi
- Voltage
- 230 V
- Iahiko hoahoa
- 20 A
- Power factor
- 0.9
- Paerewa
- NZ · AS/NZS 3008.1.2
- Roa rerenga
- 30 m
- Tikanga whakaurunga
- Kua kōpakina ki te hau
- Pāmahana taiao
- 30 °C
- Ngā ara iahiko whakarōpū
- 1
- Rahi uaua kua whakauruhia
- 2.5 mm²
- Rauemi
- Parahi
- Insulation
- PVC 75 °C
- Ngā matua
- Multicore
- Ngā waea i te whakarite
- 1
- Rohe heke voltage
- 5 %
- Impedance waho Ze
- 0.35 Ω
- Iahiko hapa ka puta pea
- 0 kA
- Kauwhata taputapu
- Kauwhata C
- Reiti taputapu
- 20 A
Ara iahiko 2.5 mm²
Ka whai
- Reiti whakatika Iz
- 23A
- Heke voltage
- 4.25%
- Earth fault loop impedance
- 0.89Ω
- Zs nui rawa mō te taputapu
- 1.53Ω
- Te rahi iti rawa e pai ana
- 2.5mm²
- Taputapu nui rawa o te ara C e whakaaetia ana e te uaua
- 20A
- Tauwehe whakatika kua whakakotahi
- ×1.00
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Rahi kaikawe kua whakaurua2.5mm²
AS/NZS 3008.1.2:2017 Table 13 p.62–64
- Whakatauhanga ripanga o 2.5 mm²23A
AS/NZS 3008.1.2:2017 Table 13 p.62–64
- Tauutu whakatika pāmahana taiao×1.00
AS/NZS 3008.1.2:2017 Tables 27(1), 27(2) p.88
- Tauwehe whakatika whakarōpū×1.00
One circuit, no grouping factor
- Tauwhiwhi whakatika kua whakakotahitia×1.00
- Ine whakatika Iz23A
AS/NZS 3000:2018 Cl 3.4
- Heke whakahiato9.78V
- Heke whakahiato ōrau4.25%
AS/NZS 3000:2018 Cl 3.6.2
- Reiti taputapu In20A
AS/NZS 3000:2018 Cl 2.5.3.1
- Rahi kaikawe whenua2.5mm²
AS/NZS 3000:2018 Table 5.1
- Ārai ara hapa whenua i 230 V wae ki te whenua0.89Ω
AS/NZS 3000:2018 Table 8.1
- Zs teitei rawa mō te taputapu1.53Ω
AS/NZS 3000:2018 Table 8.1
- Rahi iti rawa e eke ana2.5mm²
AS/NZS 3000:2018 Cl 3.4
Mō tēnei tātaitai
How this is calculated
The tool takes a circuit that is already installed and runs the five checks of the cable size calculator at its size. It uses the same code, so the two tools agree on every size.
- Current capacity. It reads the tabulated rating of the installed size for your material, insulation, core count and installation method. It multiplies the rating by the correction factors for the route to get Iz. Iz must be at or above the design current Ib.
- Voltage drop. It works out the drop for the run length, the power factor and the conductor. It compares the drop with the limit you set.
- Breaker rating. The breaker rating In must sit between the two: Ib at or below In, and In at or below Iz. The tool gives both margins.
- Loop impedance. It adds the active and earth conductor resistance to the external impedance Ze. The total Zs must stay under the maximum for the breaker curve and rating.
- Fault withstand. If you enter a prospective fault current, the conductor must withstand it for the clearing time.
- Result. The circuit passes when every check it runs passes. The tool gives the smallest standard size that passes with the same breaker, and the largest breaker of the same curve that the cable allows.
| Step | Table or clause | What it decides |
|---|---|---|
| Current rating | Table 13 or 14 for multicore, Tables 4, 5, 7 and 8 for single core | The tabulated rating of the installed size |
| Correction factors | Tables 22 to 29 and Table 2 | The factors for the route |
| Voltage drop | Tables 30, 34 and 35, AS/NZS 3000 Cl 3.6.2 | The drop over the run and its limit |
| Breaker rating | AS/NZS 3000 Cl 2.5.3.1 | That In sits between Ib and Iz |
| Earth and Zs | AS/NZS 3000 Table 5.1 and Table 8.1 | The earth conductor size and the maximum loop impedance |
| Fault withstand | Table 52 and Cl 5.3 | The fault current the conductor survives |
Tables without a standard named are in the part of AS/NZS 3008.1 you pick. AS/NZS 3008.1.1:2025 numbers them by section.
Common circuits, worked with the tool
Each line states its circuit. Every line uses multicore copper cable with PVC insulation and one circuit on the route, enclosed in air at 30 °C. Every breaker is a C curve and Ze is 0.35 Ω, on the New Zealand tables.
- Socket‑outlets, 2.5 mm² on a 20 A breaker over 30 m. It passes every check. The drop is 4.25 %, close to the 5 % limit.
- The same cable on a 32 A breaker with a 25 A load. It fails the current, drop and breaker checks. 6 mm² is the smallest size that passes.
- 4 mm² on a 32 A breaker over 20 m. It fails the breaker check, because Iz is 29 A. The largest breaker the cable allows is 25 A, and 6 mm² is the smallest size that passes on 32 A.
- Three‑phase submain, 16 mm² on a 63 A breaker over 80 m. It fails on loop impedance: Zs is 0.76 Ω against a maximum of 0.49 Ω. With this breaker, 70 mm² is the smallest size that passes.
New Zealand and Australia
The Standard select picks the part of AS/NZS 3008.1 the tool reads. For Australia, the Edition select picks 2025 or the superseded 2017 edition. The breaker and Zs rules come from AS/NZS 3000, which is the same in both countries.
What the tool does not check
The tool works from the inputs, not from a test. Measure Ze and Zs on site and compare the reading with the maximum it gives. It does not check RCD rules or discrimination between breakers.
To size a new circuit, use the cable size calculator. To read the factors for a route on their own, use the correction factors calculator.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He rahi circuit-breaker pēhea ka taea te whakamahi ki te taura 4 mm²?
Ka whakawhirinaki ki te ara. Ina kōpakina ki te hau 30 °C anake, ka reiti te parahi 4 mm² ki te 29 A i Aotearoa, nō reira ko te 25 A circuit-breaker te rahi paerewa nui rawa. Ka iti iho i te whakarōpūtanga, i te wera, i te insulation rānei. Uruhia tō ara kia pānuitia te circuit-breaker nui rawa e whakaae ana te taura.
He aha te tikanga o Ib ≤ In ≤ Iz?
Ko Ib te iahiko hoahoa o te uta, In te reiti breaker, ā, Iz te reiti taura i muri i te whakatika. Me kawe e te breaker te uta, ā, me kawe e te taura te reiti breaker. Ko te ture e whakatakotoria ana e AS/NZS 3000 Clause 2.5.3.1.
He aha te ara iahiko roa e hinga ai i te loop impedance?
He nui te earth fault loop impedance o tētahi taura roa, iti rānei. Nā reira he iti rawa te iahiko hapa hei whakahoki i te breaker i tōna tautuhi magnetic i te wā tika. Whakamahia he taura nui ake, he reiti breaker iti ake, he B curve, me te tirotiro i ngā ture RCD mō te ara iahiko.
Ka ine te taputapu i taku ara iahiko?
Kāo. Ka mahi ia mai i te rahi taura, te ara, me te impedance o waho Ze ka uru e koe. Ruri i te Ze me te Zs i te wāhi, ā, whakatauritea te panui ki te Zs teitei rawa e whakaatu ana te taputapu.
He rahi pēhea e whakaaro ai te taputapu ina hinga te ara iahiko?
Te rahi paerewa iti rawa e pahi ana i ngā tirotiro katoa ki te breaker ōrite, te ara me te uta ōrite. Koia te whakautu e hoatu ana e te taputapu rahi taura mō taua ara iahiko ōrite.
Ngā tauira mahi
- A circuit chart for a house board with solarThe circuit chart and labels for a six-circuit house board with a solar inverter: ways, devices, RCDs, MAIN SWITCH, MAIN SWITCH SOLAR and a shared neutral.
- What 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.
Kōrero o muri
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- AS/NZS 3000:2018 Cl 2.5.3.1Protective device coordination
- AS/NZS 3000:2018 Cl 3.4Current-carrying capacity
- AS/NZS 3000:2018 Cl 3.6.2Voltage drop limit
- AS/NZS 3000:2018 Table 5.1Minimum earthing conductor size by active conductor size
- AS/NZS 3000:2018 Table 8.1Maximum earth fault loop impedance multipliers by MCB curve
- AS/NZS 3008.1.2:2017 Table 4Current ratings, single‑core cable, two cables per circuit, thermoplastic 75 °C
- AS/NZS 3008.1.2:2017 Table 5Current ratings, single‑core cable, two cables per circuit, cross-linked 90 °C
- AS/NZS 3008.1.2:2017 Table 7Current ratings, single‑core cable, three cables per circuit, thermoplastic 75 °C
Ia Clause me Table, me te pēhea i manatokotia ai ia tētahi
Ngā tūtohi i arotakehia whakamutunga i te 27 Sept 2026.
Ngā taputapu hononga
- Tātaitai rahi tauraFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai earth fault loop impedanceCheck earth fault loop impedance against the maximum Zs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Kōwhiri taura māmāRead the Appendix C device rating and voltage drop tables.AS/NZS 3000
He whai hua tēnei?
He pātai, he uara rānei e kitea ana he hē? Whakapā mai.