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Diversity

richard64
Good morning all.


I have a question regarding diversity calc.

So, for example, I have a office unit that has three floors.

There is a main DB feeding the block, each floor has a submain DB feeding three single dbs.

For ease I will make all the DBs the same.

So, the single dbs supply:

3 x 16A Power circuits,

2 x 32A Shower circuits feeding a 7KW shower on each,

1 x 16A Water Heater feeding a 3 KW heater,

1 x 6A Lighting circuit feeding 6 x 20W lights.


So, for diversity I have

Power - (100% x 16) + (50% x (16 + 16) = 32A

Water Heaters - (100% x 30.4) + (100% x 30.4) + (25% x 13.04) = 64.06

Lighting - (90% x 0.52) = 0.46 

Which give a total diverse loading of 96.52 A (100A supply).


Which gives a 300A supply to each submit DB and a 900A supply to the main DB


Is this correct?

Now,  line 9 of table A2 gives a diversity of final circuits.

How would, if I should, apply this.


Thank you in advance.


Richard.

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  • 0
    I do not agree with the above assessment regarding the electric showers.

    Whilst the accepted guide is indeed to take 100% of the largest two units plus 25% of the remainder, this should in my view be applied per phase and not to the total.

    Presuming a three phase supply and that the 18 showers are connected 6 to each phase, then I would calculate on the basis of the first two showers at 100%=64 amps, and the remaining four showers at 25%=32 amps. That is 96 amps per phase for the showers.


    The principle behind diversity calculations is of course the assumption that as the number of loads increases, that the chance of them being used at the same time declines. With single phase loads, the calculation should therefore be per phase, and not in my view by taking the total and then dividing by three.


    Had the supply been single phase, then in my view, to take 100% of the first two showers, and 25% of the remaining sixteen showers would be correct. In practice we may assume three phase as single phase supplies of that capacity are almost unknown.
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  • 0
    I do not agree with the above assessment regarding the electric showers.

    Whilst the accepted guide is indeed to take 100% of the largest two units plus 25% of the remainder, this should in my view be applied per phase and not to the total.

    Presuming a three phase supply and that the 18 showers are connected 6 to each phase, then I would calculate on the basis of the first two showers at 100%=64 amps, and the remaining four showers at 25%=32 amps. That is 96 amps per phase for the showers.


    The principle behind diversity calculations is of course the assumption that as the number of loads increases, that the chance of them being used at the same time declines. With single phase loads, the calculation should therefore be per phase, and not in my view by taking the total and then dividing by three.


    Had the supply been single phase, then in my view, to take 100% of the first two showers, and 25% of the remaining sixteen showers would be correct. In practice we may assume three phase as single phase supplies of that capacity are almost unknown.
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