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Gents , For my exam i have to design the electrical installation in a house extension , upstairs is two bedrooms containing seven twin switched sockets to BS 1363 protected by BS EN 60898 type B mcb . How do i calculate the new assumed current demand of the installation if i do not know the current demand of the equipment intended to be used . There are no fixed current using appliances and no special locations. How do i come up with the design current before CF's. I can see how it works with lighting but not with power

maveric;
Depends what type of circuit your installing and area it covers, this governs your protective device size. Once you have assumed that, ie; ring circuit with 32A MCB. Then that circuit can only take the maximum your breaker allows, in this case 32A, so that is your maximum demand.
You can have, as you know as many outlets on a ring/radial circuit as you wish but you don't add up all the 13Amps to assume Maximum Demand use your breaker size.
Hope this makes sense and is helpful
KB