Tātaitai Te Roa Nui Rawa o te Ara Iahiko
Te ara roa rawa e whakaaetia ana e te heke voltage me te fault loop.
Reads AS/NZS 3008.1.2:2017 (NZ) and AS/NZS 3000:2018. Tables checked 26 Sept 2026.
Whakamātau mahi 6
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- Find the longest run for a lighting circuitThe longest route a 1.5 mm² lighting circuit on a 10 A breaker can take.
- Find the longest socket circuitThe longest run for a 20 A circuit on 2.5 mm².
- Find the longest oven circuitThe longest run for a 32 A circuit on 6 mm², by voltage drop.
- Find the longest motor circuitThe longest three‑phase run on a 16 A D‑curve breaker.
- Find the longest run at 3 %The longest run when the drop limit is 3 %.
- Find the longest heat pump runThe longest run for a 16 A C‑curve circuit on 2.5 mm².
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Kaikawe active
- 2.5 mm²
- Kaikawe whenua
- 2.5 mm²
- Insulation
- PVC
- Taputapu whakamarutanga
- Pōwhiri momo B
- Reiti taputapu
- 20 A
- Ngā wāhanga
- Wāhanga kotahi
- Voltage wāhanga ā-ingoa
- 230 V
- Iahiko hoahoa
- 20 A
- Power factor
- 0.9
- Rohe heke voltage
- 5 %
Roa teitei rawa o te huarahi
35.26m
- Te roa o te ara o te loop hapa
- 128m
- Te roa o te ara o te heke voltage
- 35.26m
- Tirotiro whakahaere
- Heke voltage
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Te roa o te ara o te loop hapa128m
AS/NZS 3000:2018 Table B1
- Ōkeroa o te kaikawe parahi i te pāmahana mahi9.01Ω/km
AS/NZS 3008.1.2:2017 Table 30, Tables 34 to 35
- Reactance0.1Ω/km
AS/NZS 3008.1.2:2017 Table 30, Tables 34 to 35
- Heke hiko ia amp mita16.31mV/A·m
AS/NZS 3008.1.2:2017 Table 30, Tables 34 to 35
- Hiko e tangohia ana te rohe heke mai i230V
AS/NZS 3000:2018 Cl 3.6.2
- Rohe heke whakahiato11.5V
AS/NZS 3000:2018 Cl 3.6.2
- Te roa o te ara o te heke voltage35.26m
AS/NZS 3000:2018 Cl 3.6.2
- Roa whakahaereHua35.26m
AS/NZS 3000:2018 Cl 3.6.2
Mō tēnei tātaitai
How this is calculated
The tool finds the longest final subcircuit route that two limits each allow. It reports which limit governs. It reads AS/NZS 3000:2018 and AS/NZS 3008.1.2:2017.
- Fault loop length. The tool reads the route length for your breaker, size and earth size from Table B1.
- Resistance and reactance. It reads these for the active conductor. The tables are Table 30 and Tables 34 and 35, for copper at operating temperature.
- Millivolts per ampere metre. It combines both values with your power factor.
- Voltage drop limit. Cl 3.6.2 sets the limit. You enter it as a percentage of the supply voltage.
- Voltage drop length. It finds the route length at which the drop equals the limit for your design current.
- Governing length. The shorter of the two lengths is the maximum route length.
| Step | Table or clause | What it decides |
|---|---|---|
| Fault loop length | AS/NZS 3000:2018 Table B1 | The longest route for the breaker to trip |
| Cable data | AS/NZS 3008.1.2:2017 Tables 30, 34 and 35 | Resistance and reactance |
| Voltage drop length | AS/NZS 3000:2018 Cl 3.6.2 | The longest route within the drop limit |
Worked example
- 2.5 mm² on a 20 A type B breaker. The earth is 2.5 mm², with PVC insulation, on a single‑phase 230 V supply. The design current is 20 A at a power factor of 0.9. The fault loop route length is 128 m. The voltage drop route length is 35.26 m. The voltage drop governs, so the maximum route length is 35.26 m.
Limits
The tool assumes copper conductors. The reactance is the Table 30 value for a multicore cable. A single‑core run reads a higher reactance for its formation.
The tool does not check the current rating of the cable. It does not add correction factors. Use the cable size calculator for the full check.
See also: Maximum length of a 20 A final subcircuit, The voltage drop limit in Cl 3.6.2 and the voltage drop calculator.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He aha te mahi a te taputapu Te Roa Nui Rawa o te Ara Iahiko?
Ka whakaatu te taputapu i ngā roa e rua. Ko te tuatahi te roa o te ara e whakaae tonu ana ki te taputapu whakamaru kia whakawehe i te wā tika. Ko te tuarua te roa e tae ana te heke voltage ki tō tepe. Ko te poto o ngā roa e rua e whakahaere ana i te ara taura.
Nō hea mai ngā roa e rua?
Ka ahu mai te roa fault loop i AS/NZS 3000:2018 Table B1 mō te wā disconnection 0.4 s i te 230 V, ka tāia ki tō voltage nominal. Ko te roa heke voltage ka whakamahi i te aukati me te reactance o AS/NZS 3008.1.2:2017 Tables 30, 34 me 35, e whakatauritea ana ki Clause 3.6.2.
He aha te takirua e kore ai e whakaatu i te fault loop length?
Ko Table B1 e tūtohi ana i tētahi rārangi tino takirua kaikawe me ngā reiti taputapu. Ko te takirua kāore i tā ki te tūtohi, kāore he roa tūtohia, nō reira ka pūrongo te taputapu i te roa heke voltage anake. Whakamahia te taputapu loop impedance hei arotake i taua takirua hei utu.
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- B1Maximum route lengths for conductor sizes and protective devices
- AS/NZS 3008.1.2:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
Ia Clause me Table, me te pēhea i manatokotia ai ia tētahi
Ngā tūtohi i arotakehia whakamutunga i te 26 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 heke voltageCalculate voltage drop on a cable run and check the limit.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
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