An estimator prices a tenancy fitout before anyone draws a cable schedule. The price still needs a demand figure, a submain size and a connection capacity. This page works one fitout through the demand tool. It then lists the calculators that carry the rest of the price stage.
The fitout
The tenancy takes a three-phase 230/400 V supply. The tool takes the phase voltage, 230 V, and converts each kW load at it. The load list holds 10 kW of lighting in group A. Group B(i) holds 48 socket-outlets. Group C(i) holds two appliances of 12 kW and 9 kW. Group D holds two motors of 18 A and 11 A. The table is C2 with the commercial column.
The clause and the table
Cl 2.2.2 of AS/NZS 3000:2018 requires the demand assessment. Table C2 gives the rule for each load group in a non-domestic installation. Table C4 covers demand upstream of a single installation.
The steps
- Group A, lighting: 43.48 A.
- Group B(i), socket-outlets up to 10 A: 157.61 A.
- Group C(i), cooking, heating and cooling appliances: 81.52 A.
- Group D, motors other than lifts: 26.25 A.
- Maximum demand, all phases: 308.86 A.
The result
The demand is 102.95 A per phase from a total of 308.86 A. The tool marks one point. The per phase figure assumes an even spread across the three phases. The standard takes the heaviest loaded phase, so allocate the loads per phase where the arrangement is uneven.
That figure sets the connection application, the main switch rating and the starting point for the submain size.
The rest of the price stage
Maximum demand turns a load list into a current, as above. Table C1 covers a house or a block of living units. Table C2 covers everything else.
Full load current converts a nameplate in kW or kVA into amperes. Use it for a chiller, a kitchen or a workplace charger before the load goes into the demand list.
Three-phase power turns the demand current back into kVA for the network application.
Voltage drop gives a price stage check on a submain length. It runs from one cable size and one length. Use it while the route is still a guess.
Cable size applies capacity, drop, device rating, loop impedance and fault withstand together. Run it once the route is fixed.
Conduit fill sets the conduit size for the civil line item.
Generator and transformer give a full load current from one rating, for the temporary supply and the substation lines.
The workflow
Every input sits in the page address. Copy the link to send the same assessment to a reviewer or an estimator on another site. An account saves a calculation under a project name, so a tender keeps its own set.
A PDF report carries the inputs, the result and the table references. The free plan holds 10 saved calculations and prints a PDF with an AmpSize footer line. Pro costs NZ$5 a month or NZ$45 a year. Pro adds unlimited saves, projects and a PDF with a branding block.
What AmpSize does not do
- It holds no labour rates, material prices or margins.
- It does not produce a bill of materials or a takeoff.
- It exports PDF reports and shareable links. A CSV schedule of a project is a Pro export.
- It does not import a drawing, a schedule or a spreadsheet.
- It does not integrate with an accounting or estimating package.
- It assesses demand by table only. It does not read metered data.
Compare it with a full estimating package on those grounds. Prices and feature lists change, so check the vendor's site for the current position before choosing one.
For cable sizing, the cable size calculators compared table sets every NZ and AU tool in it side by side.
This page is a design aid. Verify every value against the current edition of the standard.
See also: Domestic maximum demand with Table C1, Commercial maximum demand with Table C2 and Maximum demand and diversity.