A tender needs a demand figure before the design exists. Table C2 of AS/NZS 3000:2018 gives one from a load count. The figure is good enough to price a supply, a main switchboard and consumer mains.
The inputs
A commercial tenancy on a three‑phase 230/400 V supply. The Table C2 commercial column applies. The tool takes the phase voltage, 230 V line to neutral, not the 400 V between lines. It converts each kW load at that voltage.
- Group A, lighting: 12 kW
- Group B(i), socket outlets up to 10 A: 60 points
- Group C(i), cooking, heating and cooling appliances: 15 kW, 10 kW and 8 kW
- Group D, motors: 30 A, 22 A and 15 A
Two of those groups take a list of individual items rather than a count. Table C2 treats the largest item in such a group differently from the rest, so the items go in separately.
The clause and the table
Cl 2.2.2 of AS/NZS 3000:2018 sets out the methods for assessing maximum demand. Table C2 is the demand table for installations other than a single domestic installation or a block of living units. It has a residential column and a commercial column.
Table C4 covers diversity applied further upstream, where several installations share a supply.
The group letters are the whole method. Each letter carries its own rule, and the rules are not the same. A sum of the connected load is not a Table C2 assessment.
The steps
The tool applies the rule for each group in turn and reports the demand it produces.
- Group A, lighting: 52.17 A
- Group B(i), socket outlets: 196.74 A
- Group C(i), appliances: 123.91 A
- Group D, motors: 54 A
Each line names Table C2 as its source. The socket outlet group carries the largest share here, which is the usual pattern in a commercial fitout.
The result
- Maximum demand, all phases: 426.82 A
- Maximum demand per phase: 142.27 A
The per-phase figure is the one the network application asks for. It is also the figure that sets the consumer mains and the main switch rating.
Read the per-phase caveat
The tool divides the total by three. That assumes the load spreads evenly over the three phases. The standard takes the heaviest loaded phase instead.
At tender stage the even split is a reasonable estimate, because the phase allocation does not yet exist. Once the board schedule is drawn, allocate each group to its phases and check the heaviest one. An uneven fitout raises the governing figure above 142.27 A while the total stays at 426.82 A.
A single‑phase item such as a 10 kW appliance lands entirely on one phase. Several of them on the same phase move the result. Motors are usually three‑phase and spread on their own.
Where the number goes next
142.27 A per phase is a design current. It feeds the cable size tool as the consumer mains load. It also sets the rating band for the main switch. The three‑phase power tool converts it to kVA for a network connection application.
Revisit the assessment when the load list firms up. A tender count of 60 socket outlets and a built count of 85 give different mains. Record the load list beside the result so the change is visible when it happens.
This page is a design aid. Verify every value against the current edition of the standard.
See also: Domestic maximum demand with Table C1, Cable size for a 32 A single‑phase 25 m run and Maximum demand and diversity.