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Construction site supply calculator

Supply, RCD and test rules for a construction site.

AS/NZS 3012

Reads AS/NZS 3012:2019. Tables checked 1 Oct 2026.

Try a job 6

Each job fills in example values. Replace them with your values.

Inputs

Worked example with the default inputs. The live calculator replaces it when the page loads.

Country
New Zealand
Supply source
An electricity distributor's main
Circuit
A final sub-circuit that starts at the construction switchboard
Exception that applies
None
What you are verifying
Portable gear you carry to the job: tools and appliances, leads, cord extension sets, generators and inverters
The RCD is a portable RCD
Yes
This is hire equipment
No
An arc welder is incorporated into the generating set
No

RCD-based additional protection

Required, 30 mA

Supply clause
AS/NZS 3012:2019 Cl 2.1.1(a)
Protection clause
AS/NZS 3012:2019 Cl 2.4.6.1
Inspection and test interval
3months
RCD push-button test
Connect the portable RCD to the supply socket, then press its test button before you connect equipment. Do this again every day while it is in use
RCD operating time test
3months

This result is a design aid. Verify it against the current standard.

Calculation steps

  1. Supply arrangementAn electricity distributor's main

    AS/NZS 3012:2019 Cl 2.1.1(a)

  2. Additional protection requiredYes

    AS/NZS 3012:2019 Cl 2.4.6.1

  3. Maximum rated residual current30mA

    AS/NZS 3012:2019 Cl 2.4.6.1

  4. Inspection and test interval3months

    AS/NZS 3012:2019 Table 6

  5. RCD push-button testConnect the portable RCD to the supply socket, then press its test button before you connect equipment. Do this again every day while it is in use

    AS/NZS 3012:2019 Table 6

  6. RCD operating time test3months

    AS/NZS 3012:2019 Table 6

  7. Socket-outlets on a switchboard10A

    AS/NZS 3012:2019 Cl 2.3.4

  8. Isolating switch marking height6mm

    AS/NZS 3012:2019 Cl 2.4.4

About this calculator

How this is calculated

The tool gives the supply arrangement and the RCD protection for a construction or demolition site. It reads AS/NZS 3012:2019.

  1. Supply arrangement. You pick the source, such as a distributor main. The tool finds the supply clause, here Cl 2.1.1(a).
  2. Additional protection. It reads Cl 2.4.6.1 for the circuit type and the exceptions. It says whether RCD protection is required.
  3. Residual current. It gives the maximum rated residual current for that circuit.
  4. Test intervals. It reads Table 6 for the inspection and test interval of the equipment.
  5. RCD tests. Table 6 also gives the push-button test and the operating time test.
  6. Switchboard points. It points at Cl 2.3.4 for socket-outlets and Cl 2.4.4 for the isolating switch marking.

Worked example

Limits

The RCD must trip on every active conductor and the neutral. Where a board feeds two or more lighting circuits, spread them across the RCDs. New Zealand sites also complete a Record of Assessment in the Appendix G form. The tool does not size cable. It does not check the cord length.

The tool gives one supply arrangement at a time. Pick the arrangement that matches the board in front of you. Then read the clause the tool names. Test the RCD on the site, as the intervals say. Record the results with the date.

See also: Construction site supplies to AS/NZS 3012, Builder's pole, RCDs and cord lengths and Site cord length.

Questions

Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.

What does the construction site supply tool do?

The tool reports the supply arrangements allowed on a site under construction or demolition, the RCD protection for the circuit, and the inspection and test intervals for the equipment. It works to AS/NZS 3012:2019.

What RCD does a construction site need?

Clause 2.4.6.1 protects every final sub-circuit run from the construction switchboard with an RCD of at most 30 mA, tripping on every active conductor and the neutral. Three exceptions apply: mechanical operation at risk, SELV or PELV supply, and a safety isolating transformer.

How often are site RCDs tested?

Plug in a portable RCD, or start the generator or inverter that carries one, then press its test button before you connect equipment. Do this every day it is in use. Press a fixed RCD's test button monthly. Do the operating-time test every 3 months on a portable RCD, every 12 months on a fixed one.

Which supplies are allowed on a site?

Clause 2.1.1 allows an electricity distributor's main, an existing switchboard of the permanent installation, a low voltage generating set complying with and installed to AS/NZS 3010, or an inverter to AS/NZS 4763. That is AS/NZS 3012:2019; the 2010 edition also named AS 2790 for the generator. Isolated winding types supply only a separated circuit.

Does the tool cover insulation resistance for welders?

Yes, but only for arc welders built into generating sets, which is the scope Clause 3.5.4 gives Table 7 of AS/NZS 3012:2019. Other equipment follows AS/NZS 3760 instead; AmpSize's Test and Tag tool covers those checks.

Clauses and tables this tool reads

Every clause and table, with how each was verified

Tables last checked on 1 Oct 2026.

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