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Topic Title: Power requirements
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Created On: 02 July 2012 10:16 AM
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 02 July 2012 10:16 AM
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Sparky64

Posts: 1
Joined: 02 July 2012

I have been asked to calculate the power requirements for a new electrical installation in order to specify cable and MCCB sizes. This is something i have never done before and would like to know how i go about it.

I was going to add up all the Motor & transformer KW/KVA ratings and then calculate my current from this, is this correct?

Do i have to calculate the power requirements for every single device, every contactor and relay?

Any help would be greatly appreciated.
 05 July 2012 11:23 AM
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neilparsons

Posts: 31
Joined: 29 October 2002

Just adding all the loads up on all but the smallest installation may give a pessimistically high maximum demand.

You need to look at diversity (how many of the loads will be on at the same time) and utilisation factors (will a load, say a motor be used to its maximum).

By applying diversity and utilisation factors you should come up with a realistic figure, you then need to add a bit (could be 25%) for future expansion.

You normally need to have a good understanding of how the installation will be used. You can also use power monitoring if you have a similar existing installation.
 16 October 2012 06:37 PM
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MAXMIRA

Posts: 78
Joined: 25 January 2011

Sparky, I'd recommend first listing all of the loads then looking at them on an individual basis before applying an overall diversification.
 23 October 2012 12:41 PM
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alexmoroz1987

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Joined: 14 October 2012

I agree with Maxmira. you have to look on an individual basis. Hope you will be able to sort it out.
 10 March 2013 05:08 PM
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deepakjnu10

Posts: 1
Joined: 10 March 2013

Just adding all the loads up on all but the smallest installation may give a pessimistically high maximum demand.

You need to look at diversity (how many of the loads will be on at the same time) and utilisation factors (will a load, say a motor be used to its maximum).

By applying diversity and utilisation factors you should come up with a realistic figure, you then need to add a bit (could be 25%) for future expansion.

You normally need to have a good understanding of how the installation will be used. You can also use power monitoring if you have a similar existing installation.
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