Two regulations in the Electricity (Safety) Regulations 2010 shape how a New Zealand installation is designed and recorded. Both connect to a number the maximum demand tool produces.
The question
A large house has a long load schedule. Where does its assessed maximum demand sit against the threshold named in reg 59(1)?
The inputs
- Table C1, single domestic installation
- 230 V, single phase
- A(i) Lighting: 45 points
- B(i) Socket‑outlets and connected equipment up to 10 A: 40 points
- C Ranges, cooking appliances and laundry equipment: 18 kW connected
- F Storage water heaters: 9 kW connected
The regulations and the table
Reg 57 sets the safety requirement that an installation has to meet. Reg 59 names the routes to that requirement. Reg 59(1) covers the ordinary route. Reg 59(2) opens a second route above a stated threshold. The threshold runs per phase, so a multiphase supply takes a different figure.
Reg 63 covers the certification of completed work. Reg 74C covers the record that follows that work. This page cites both by number.
Table C1 of AS/NZS 3000:2018 is the assessment method for a single domestic installation. The regulations set the threshold. The table produces the number that is compared with it.
The steps
The maximum demand tool applies the Table C1 rule for each group in turn.
- A(i) Lighting: 7 A
- B(i) Socket‑outlets and connected equipment up to 10 A: 15 A
- C Ranges, cooking appliances and laundry equipment: 39.13 A
- F Storage water heaters: 39.13 A
Groups C and F arrive in kilowatts. The tool converts each one at 230 V, then applies the group rule. An oven bank and a water heater bank can therefore land on the same current.
The tool adds the four lines and divides by the phase count. One phase carries the whole load.
The result
The assessed maximum demand is 100.26 A, and the per phase figure is the same 100.26 A.
That figure sits above the reg 59(1) threshold of 80 A per phase, so the tool raises a note. The note records the two routes that reg 59(2) then allows: Part 2 of AS/NZS 3000, or a certified Part 1 design.
The note changes nothing about the arithmetic. It marks the point where the design route in the regulations changes. It points a reader at reg 59 rather than at the standard.
The table choice matters as much as the load schedule. Table C1 covers a single domestic installation and a block of living units. Table C2 covers other installations. The tool raises the reg 59(1) note on a Table C1 assessment only, because the threshold sits in a domestic context.
The mode choice changes the arithmetic again. A block of living units divides the unit count across the phases before the group rules run. A single domestic installation does not. Set the table and the mode before entering a single load row.
Two habits keep this check honest. Enter the connected load that the installation will actually carry, because the group rules scale with it. Then re-read the current reprint of the regulations, since thresholds and regulation numbers both change between reprints.
This page is a design aid. Verify every value against the current edition of the standard.
See also: Domestic maximum demand with Table C1, AS/NZS 3000 Tables C1 and C2: demand groups and Who may do electrical work in NZ.