Tātaitai correction factor
Pānuitia ia tauwehe whakatika me te reiti e hiahiatia ana e tētahi taura.
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.
- Find the correction factors in a hot ceilingThe factor for four circuits in a 50 °C ceiling space, and the rating the cable needs.
- Find the correction factors for a buried cableThe soil, depth and grouping factors for two buried three‑phase circuits.
- Find the factor for nine circuitsThe grouping factor for nine circuits on a tray.
- Find the factor on a 50 °C roofThe ambient factor at 50 °C.
- Find the factors in poor soilThe soil and depth factors at 2.5 K·m/W and 1 m.
- Find the factor for a harmonic loadThe factor for 40 % third harmonic in a four‑core cable.
- Compare the factors in AustraliaThe factors for 45 °C and four grouped circuits on the Australian tables.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Paerewa
- NZ · AS/NZS 3008.1.2
- Tikanga whakaurunga
- Kua kōpakina ki te hau
- Pāmahana taiao
- 40 °C
- Ngā ara iahiko whakarōpū
- 3
- Ngā wāhanga
- Wāhanga kotahi
- Iahiko hoahoa
- 32 A
- Rahi taura
- 6 mm²
- Rauemi
- Parahi
- Insulation
- PVC 75 °C
- Ngā matua
- Multicore
- Ngā waea i te whakarite
- 1
Tauwehe whakatika kua whakakotahi
0.62x
- Au ripanga hiahiatia
- 51.95A
- Reiti ripanga o te 6 mm²
- 38A
- Reiti whakatika Iz
- 23.41A
- Tauutu whakatika pāmahana taiao
- ×0.88
- Tauwehe whakatika whakarōpū
- ×0.70
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Tauutu whakatika pāmahana taiao×0.88
AS/NZS 3008.1.2:2017 Table 27(1) p.88
- Tauwehe whakatika whakarōpū×0.70
AS/NZS 3008.1.2:2017 Tables 22, 25(1), 25(2) p.79, p.84–85
- Tauwhiwhi whakatika kua whakakotahitiaHua×0.62
- Au ripanga e hiahiatia ana51.95A
AS/NZS 3000:2018 Cl 3.4
- Whakatauhanga ripanga o 6 mm²38A
AS/NZS 3008.1.2:2017 Table 13 p.62–64
- Ine whakatika Iz23.41A
AS/NZS 3000:2018 Cl 3.4
Mō tēnei tātaitai
How this is calculated
The tool reads every factor that lowers or raises the current a cable can carry on your route. It is the same code the cable size calculator runs before it tests each size.
- Ambient. It reads the factor for the air temperature, or the soil temperature on a buried route. AS/NZS 3008.1.2 rates New Zealand cables for 30 °C air and 15 °C soil. AS/NZS 3008.1.1 rates Australian cables for 40 °C air and 25 °C soil, so a cooler route gives a factor above 1.
- Grouping. It reads the factor for the circuits that share the route, by how they sit. On a tray, ladder, rack or cleats, pick the cable support. Each parallel cable set counts as a circuit.
- Buried cable. For a buried route it reads the soil thermal resistivity factor and the burial depth factor. Cable buried direct reads its depth factor by conductor size.
- Harmonics. On three phases with third harmonic current, it reads the reduction factor. Above 33 %, it sizes on the neutral current.
- Product. It multiplies the factors into one correction factor (derating factor in 2017). It divides the design current by that factor to give the tabulated current the cable needs.
- One size. It reads the tabulated rating of the size you pick and multiplies it by the factor. The result is Iz, which it checks against the design current.
| Step | Table or clause | What it decides |
|---|---|---|
| Ambient | Tables 27(1) and 27(2) | The factor for the air or soil temperature |
| Grouping | Tables 22, 25(1) and 25(2) | The factor for circuits run together |
| Cable support | Tables 23 and 24 | The factor on a tray, ladder, rack or cleats |
| Buried cable | Table 29, Tables 28(1) and 28(2) | The factors for soil resistivity and depth |
| Harmonics | Table 2 and Cl 3.5.9 | The reduction for third harmonic current in the neutral |
| Required current | AS/NZS 3000 Cl 3.4 | The current the cable must carry in the table |
| Current rating | Table 13 or 14 for multicore, Tables 4, 5, 7 and 8 for single core | The tabulated rating of the size you pick |
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, such as Table 3.44 for Table 27(1).
Common routes, worked with the tool
Each line states its route. Every line uses multicore copper cable with PVC insulation, except where a line names single‑core cable.
- Three circuits enclosed in 40 °C air, 32 A on 6 mm². The factors multiply to 0.62 x. The cable needs a tabulated 51.95 A, and 6 mm² carries only 23.41 A on this route.
- The same route on 16 mm². The factors still multiply to 0.62 x, and the cable needs a tabulated 51.95 A. 16 mm² carries 40.66 A, above the 32 A design current.
- Buried direct in Australia, 100 A on 35 mm² single‑core. Soil at 20 °C with a resistivity of 2 K·m/W, 1 m deep. The factors multiply to 0.8 x, and the cable needs a tabulated 125.31 A.
- Four three‑phase circuits touching, 80 A with 40 % third harmonic on 50 mm². The neutral carries 96 A, so the tool sizes on it. The factors multiply to 0.56 x, and the cable needs a tabulated 171.74 A.
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 2025 edition changed several ambient and grouping factors, so run both when you check an older design.
To size the cable from these factors, use the cable size calculator. To check a cable that is already installed, use the circuit check.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He rite te correction factor ki te derating factor?
Āe. Ka kīia e AS/NZS 3008.1.1:2025 he correction factors. Ka kīia e ngā wāhanga 2017 he derating factors. Ka whakareatia e ngā mea e rua te reiti tūtohi kia riro ai te iahiko e kawea ana e te taura i tōu ara.
Me pēhea te whakakotahi i ngā tauwehe?
Whakareatia ērā. Ka hāngai te taiao, te whakarōpū, te aukati oneone, te hōhonu tanu me te tauwehe harmonic ki te reiti. Wehea te iahiko hoahoa ki te hua kia tiki ai i te iahiko ripanga e hiahiatia ana e te taura.
He aha te taura Ahitereiria i te 30 °C e tika ai te tauwehe nui ake i te 1?
Ka whakatauhia e AS/NZS 3008.1.1 ngā taura mō te hau 40 °C me te oneone 25 °C. Ka taea e te ara mātao te kawe nui ake i te taura. Ka whakatauhia e AS/NZS 3008.1.2 ngā taura o Aotearoa mō te hau 30 °C me te oneone 15 °C.
Ka tatauria ngā taura parallel hei ara iahiko whakarōpūtanga?
Āe. Ka tatauria ia huinga taura o tētahi ara iahiko parallel hei ara iahiko i te rōpū. Ko ngā ara iahiko e toru o ngā huinga parallel e rua ka pānui i te tauwehe mō ngā ara iahiko e ono.
He aha te rerekē o te depth factor mō tētahi taura nui ake?
Mō tētahi taura tanu tōtika, ka wehea e te ripanga hōhonu te tauwehe e te rahi kaikawe: tae atu ki te 50 mm², neke atu i te 50 tae atu ki te 300 mm², ā, neke atu i te 300 mm². Ka pānui te taputapu i te wehenga o te rahi e kōwhiria ana e koe.
Ngā tauira mahi
- Cable 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.
- Downlights in an insulated ceilingRe-insulate a NZ ceiling with downlights in it. Check which may be covered, which only abutted, which must come out, and the clearances and roof space sign.
- Three 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.
Kōrero o muri
- Downlights and insulation: IC-4, CA90 and Non‑ICThe 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.
- Cable tray fill: one layer, tiers and groupingHow 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.
- Correction factors in the 2017 and 2025 editionsWhat 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.
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- AS/NZS 3000:2018 Cl 3.4Current-carrying capacity
- AS/NZS 3008.1.2:2017 Cl 3.5.9Third harmonic current in the neutral
- AS/NZS 3008.1.2:2017 Table 2Reduction factors for harmonic currents in 4- and 5‑core cables
- AS/NZS 3008.1.2:2017 Table 13Current ratings, multicore cable with three or four cores, thermoplastic 75 °C
- AS/NZS 3008.1.2:2017 Table 22, 25(1), 25(2)Grouping factors for bunched circuits, buried circuits and underground wiring enclosures
- AS/NZS 3008.1.2:2017 Table 23Grouping factors for single‑core circuits on trays, ladder supports, racks and cleats in air
- AS/NZS 3008.1.2:2017 Table 24Grouping factors for multicore cables on trays, ladder supports, racks and cleats in air
- AS/NZS 3008.1.2:2017 Table 27(1), 27(2)Rating factors for air and soil ambient temperature
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 heke voltageCalculate voltage drop on a cable run and check the limit.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Whakakī cable tray me te ladderTray or ladder width, tiers, kg/m and the grouping factor.AS/NZS 3008.1
He whai hua tēnei?
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