Chapter A General rules of electrical installation design

A18
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A - General rules of electrical installation design
4 Power loading of an installation
Factor of simultaneity for distribution boards
Figure A12 shows hypothetical values of ks for a distribution board supplying a
number of circuits for which there is no indication of the manner in which the total
load divides between them.
If the circuits are mainly for lighting loads, it is prudent to adopt ks values close to
unity.
Fig. A12 : Factor of simultaneity for distribution boards (IEC 60439)
Circuit function Factor of simultaneity (ks)
Lighting 1
Heating and air conditioning 1
Socket-outlets 0.1 to 0.2 (1)
Lifts and catering hoist (2) b For the most powerful
motor 1
b For the second most
powerful motor 0.75
b For all motors 0.60
(1) In certain cases, notably in industrial installations, this factor can be higher.
(2) The current to take into consideration is equal to the nominal current of the motor,
increased by a third of its starting current.
Fig. A13 : Factor of simultaneity according to circuit function
4.4 Example of application of factors ku and ks
An example in the estimation of actual maximum kVA demands at all levels of an
installation, from each load position to the point of supply is given Fig. A14 (opposite
page).
In this example, the total installed apparent power is 126.6 kVA, which corresponds
to an actual (estimated) maximum value at the LV terminals of the MV/LV transformer
of 65 kVA only.
Note: in order to select cable sizes for the distribution circuits of an installation, the
current I (in amps) through a circuit is determined from the equation:
I = kVA x 10
U
3
3
where kVA is the actual maximum 3-phase apparent-power value shown on the
diagram for the circuit concerned, and U is the phase to- phase voltage (in volts).
4.5 Diversity factor
The term diversity factor, as defined in IEC standards, is identical to the factor of
simultaneity (ks) used in this guide, as described in 4.3. In some English-speaking
countries however (at the time of writing) diversity factor is the inverse of ks i.e. it is
always u 1.
Schneider Electric - Electrical installation guide 2008
Number of Factor of
circuits simultaneity (ks)
Assemblies entirely tested 0.9
2 and 3
4 and 5 0.8
6 to 9 0.7
10 and more 0.6
Assemblies partially tested 1.0
in every case choose
Factor of simultaneity according to circuit function
ks factors which may be used for circuits supplying commonly-occurring loads, are
shown in Figure A13.