Introduction
The maximum demand calculator of Cable Pro Web software is explained in this tutorial.
All the installation types including Domestic, Living Units and Industrial are covered as well as all the Load Groups from the Standard AS/NZS 3000 Wiring Rules. You can also specify custom diversity factors.
You can add any number of loads, of any type, in any order to a maximum demand calculation. The software automatically applies the rules from the standard and automatically balances the single phase loads across the phases to determine the optimal maximum demand.
Refer to the article which explains how the Automatic Maximum Demand calculations function.
In this video we explain the main user interface, how to add loads, and we perform several maximum demand calculations.
Main window explained
Starting with the main window of the maximum demand calculator.
The maximum demand calculator window is divided into two main sections: The loads summary including quantity per phase and loading per phase as well as the maximum demand results.
The load information summarises the input data for the loads, such as the description, installation type and load types. Additionally, if applicable, the input rating will be shown. The quantity per phase section shows how many points for a particular load have been assigned to a particular phase. The loading per phase section shows the calculated load current per phase for that particular load.
The Maximum Demand section shows the final results. The total loading per phase is displayed where each value is the sum of the load currents for that phase. Additionally, the phase with the highest load is also displayed and this is important because this is the Maximum Demand for the installation. The current imbalance between phases is also calculated. When automatic phase balancing mode is selected the software aims to keep the imbalance as low as possible when calculating the maximum demand.
The maximum demand results are updated when loads are added or changed. The software may also automatically adjust the quantities per phase and the loading per phase to reduce the maximum demand to as low as possible. You can change the order of the loads in the calculation or edit the load details using the drop down. Note that the order of the loads in the calculation makes no difference in the calculated results.
Adding loads
When you press the Add load button a pop-up will appear.
Firstly, there is the electrical installation drop down, which determines which table of maximum demand rules from Appendix C of AS/NZS 3000 is used. You can choose from single domestic or blocks of living units which covers Table C1 and residential institutions, or industrial facilities which covers Table C2. Note that the electrical installation type is not locked, and you can mix load groups from different installation types if needed.
Refer to the article which contains the Maximum Demand tables.
Next, the load group, lists the main types of load categories which can be added. The options in this drop-down menu will differ depending on the electrical installation you selected. Custom loads are also selected from the Load Groups dropdown – with custom loads you can enter your own diversity factor as a percentage.
Where applicable, you also need to select the Subgroup for the selected Load Group.
Once the Load Group and Subgroup is selected the relevant rule is displayed and comes from the tables in the standards. The rules will be automatically applied by the software.
Description of the load is optional but recommended. You must select whether the load is a 1-phase or a 3-phase load and you may be required to enter the rating in current or power for each individual load point.
The Quantity determines how many instances of this load will be attached to the supply. [Highlight quantity]
For single phase loads the Phase allocation dropdown is shown. This input determines whether the single-phase loads will be automatically distributed across the phases to minimise the maximum demand. Alternatively, you can specify or lock the quantities per phase by entering the quantities under the phase columns.
Example maximum demand calculations
There are five (5) worked examples taken from AS/NZS 3000 given in the video tutorial as follows:
1) Single phase domestic installation – based on Example 1 from Appendix C.
2) Three phase domestic installation – based on Example 2 from Appendix C.
3) Blocks of living units installation – based on Example 3 from Appendix C.
4) Motel complex installation – based on Example 4 from Appendix C.
5) Factory installation – based on Example 5 from Appendix C.
