Method of Maximum Demand

Method of Maximum Demand Calc's

1.   For domestic installations covered by Table C1 Columns 3 to 5 (Blocks of Living Units) the maximum demand for load groups A to G are calculated for one phase. For load groups H to M (Communal loads) the loads are distributed across three phases and balanced as accurately as possible. The largest load phase from the communal load groups (H to M) is then added to the maximum demand calculated for load groups A to G giving the final maximum demand

2.   In the particular case of load groups A, B(i), C, E and F for blocks of living units of more than 1 units per phase. The questions are framed to ask you the total number of appliances in the development as distinct from asking the total number of units in the development, which appears in the Standard.

The questions are asked in this manner so that if the number of appliances varies from the number of units then the requirements of footnote (c) to Table C1 of AS3000:2000 can be incorporated. This clause allows maximum demand to be calculated by using the number of appliances in development in lieu of the number of units.

Where the user feels that the number of units should be entered instead of the number of appliances then you should read the word units in place of the word appliances in questions for these load groups. Remember that this only applies to load groups listed above for blocks of living units with more than 1 unit per phase.

Also NOTE that the total number of units in the development should be entered, not the number of units per phase.

3.   The calculation of maximum demand for non-domestic installations is based on the requirements of clause C4.3 and Table C2. In these cases the loads are distributed across the three phases, the relevant percentage factors are applied and the loads are then balanced as far as possible by the program. The program will then display in tabular form, the maximum demand for all selected load groups and the total maximum demand on all phases. 

4.   Note should also be taken of the calculation of staggered loading factors. These occur where subsequent pieces of equipment (possibly of lesser loading) are applied at different loading factors. See for example Group B(i) (GPO's) in Column 2 of Table C2, where the first GPO applies 1000 watts, and subsequent GPO's apply 400 watts.

The staggered load factors are calculated as follows. If the number of supply phases exceeds the connected phases of the item, then the items are applied at the first loading factor until the total number of connected phases matches the supply phases.

 As an example, consider a three-phase supply with single phase GPO's. The number of supply phases is 3, and the number of connected phases is 1. Therefore the first three GPO's are applied at 1000 watts.

As another example, consider a three phase supply with single phase Fuel Dispensing motors, which is Group F in Table C2. Again, the number of supply phases is 3, and the number of connected phases is 1. Therefore the first three motors are applied at 100%, the next three are applied at 50%, and the subsequent motors are applied at 25%. Thus each band of staggered percentages applies until all the supply phases have been covered.

Please refer to Maximum Demand Templates for instructions on editing the default calculation method and creating your own.