Tables C1 and C2 of AS/NZS 3000:2018 hold the demand rules for the calculation method in Cl 2.2.2. They turn a list of connected load into a current the mains must carry.
What the tables govern
Cl 2.2.2 offers more than one way to assess maximum demand. The table method is the one most designers use, because it produces a defensible figure from a load schedule.
Each table sorts load into lettered groups. A group is a category of load, not a circuit. Lighting sits in one group, socket outlets in another, fixed heating in another, motors in another. Each group carries its own rule.
The rules differ in shape. Some groups take a count and apply an allowance per item. Some take a list of individual ratings and treat the largest differently from the rest. The designer assesses other groups directly, and those groups contribute nothing on their own.
Table C4 covers the diversity that applies upstream, where several installations share a supply.
Choosing the table
Table C1 applies to a single domestic installation or a block of living units. Table C2 applies to other installations, and it has a residential column and a commercial column.
Choose the table and the mode before you enter any load. They change which rule every group follows. A load entered under the wrong table gives a wrong figure at every line.
Which tools read the tables
The maximum demand tool reads both. It shows the demand for each group on its own line, then the total and the per-phase figure. The three-phase power tool converts that current into a kVA figure for a network connection application.
The inputs
A commercial tenancy on a three-phase supply, taken through Table C2 on the commercial column.
- Supply: 230/400 V, three phase. The tool takes the phase voltage, 230 V.
- Group A: 10 kW
- Group B(i): 45 socket-outlets
- Group C(i): two items, 9 kW and 6 kW
- Group D: two motors, 18 A and 11 A
The steps
The engine applies each group rule in turn and reports the demand per group.
- Group A: 43.48 A
- Group B(i): 147.83 A
- Group C(i): 58.7 A
- Group D: 26.25 A
Each line names the table and the column that produced it. Groups entered in kilowatts pass through the phase voltage, 230 V line to neutral, not the 400 V between lines. The group rule sets how much of the connected load counts.
The result
The total across all phases is 276.26 A. Divided across three phases, that is 92.09 A per phase.
The engine attaches a note to the per-phase figure. The figure assumes the load spreads evenly over the three phases. The standard takes the heaviest loaded phase instead.
That note matters on a real schedule. A three-phase motor spreads evenly. A bank of single-phase heaters on one phase does not. Allocate the single-phase load per phase yourself, then check the heaviest phase against the supply.
Where the figure goes next
The per-phase current sizes the consumer mains and sets the main switch rating. It also goes on the network connection application, usually converted to kVA.
The tool adds a note once the demand passes the thresholds in the Electricity (Safety) Regulations 2010 reg 59. This page cites that regulation by number only.
This page is a design aid. Verify every value against the current edition of the standard.