CFEWH SERIES 1-10 /20 | INSTALLATION Manual © February 2021 MicroHeat Technologies Pty LTD
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Maximum Electrical Demand Calculation
Section C2.1 After Diversity Maximum Demand
1
As indicated in Clause 2.5 (and explained in Paragraph B3.2), the current in a circuit must not exceed the current rating
of the circuit protective device
–
and this, in turn, must not exceed the current-carrying capacity of the circuit conductors.
For circuits supplying a single item of equipment, the circuit current is simply the nominal load current of the equipment
(eg: a 10000W 230/400V three-phase heater has a full per
–
phase load current of 14.5A). The circuit conductors and the
protective device must have a current carrying capacity of not less than 16A (nearest standard rating).
Where more than one item of equipment is connected, the circuit current could be simply assessed as the sum of the
individual equipment load currents. While this would provide a safe and conservative solution, it does not take account
of the normal operating conditions during which all equipment is not operating simultaneously at full load or for long
periods (eg: submains to a distribution board associated with numerous socket outlet circuits). Under such conditions,
the circuit current is estimated using diversity factors and is
often described as the ‘after diversity maximum
demand’.
As stated (in Clause 2.2.2), maximum demand current can be determined by one of four methods
–
calculation,
assessment, measurement or limitation. The following paragraphs of the Appendix C provide information and examples
regarding the application of the calculation method for determining maximum
demand current in consumers’ mains and
submains only.
Section C2.3 Domestic Installations C2.3.1 Method
2
Table C1 provides an allocation of load for different
types of equipment connected to consumers’
mains or submains in
a single or multiple domestic installations. The load current is calculated for each equipment load group in the installation
or affected part thereof, and these contributions are added together to achieve the maximum demand current. The
accompanying notes provide clarification of certain provisions and the examples demonstrate how the calculation is
made.
1
AS/NZS 3000:007 Electrical_installations
2
AS/NZS 3000:007 Electrical_installations
TABLE C1
MAXIMUM DEMAND
– SINGLE AND MULTIPLE DOMESTIC ELECTRICAL INSTALLATIONS
