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The diversity of Diversity

WireWeHere

Everyone seems to have a slightly different way of calculating Diversity for sockets. I've seen it done as 100% of 'the main' circuit rating plus 40% of each subsequent circuit. Another approach is 100% of the highest power appliance on each circuit plus 40% of all the other appliances. Either way, I end up with an unrealistically high value for my calculation.

I want one circuit for each of Kitchen, Utility, rest of GF, FF and attic. Each would be 32A and so the first approach makes for 32A + 40% x 4 x 32A = 83A. If I tot up appliances and include a possible portable heater or hair dryer in each of GF, FF and attic I end up with around 80A (no shower and not including the cooker). I'm using 2kW → 8.7A for the highest power appliance in each circuit (kettle in kitchen, iron or drier in utility, heater in GF, heater or hair drier in each of FF and loft). Those items alone come to 5 * 8.7A = 44A. Adding 40% of toaster, microwave, computers etc etc ramps things up quite a bit and when I did a list it totalled 80A for sockets, but the list isn't much more than I'd expect in a general house. I used quite high values for each appliance (e.g. toaster 1400W, Drier 2kW, Iron 2.8kW, vacuum cleaner 550W)

The lights are about 3A but the electric cooker adds 30A and so the total exceeds 100A. Am I being too conscientious?

Is it reasonable to ignore (the possibility of) portable heaters if the house is well insulated and centrally heated? Doing so, and using 1kW→4.4A for the hair driers would give me a socket total or around 65A and house total of 95A so OK against the 100A max for a single main switch/fuse.

Sorry for the basic nature of my question, but everyone has a different approach and this is my first Diversity calculation.

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    Further to that, in the days when pipe smoke was popular, and loads were calculated on floor areas served,  we had 3 ‘standard circuit’ choices that allowed an unlimited number of 13A sockets these were  

    1. A ring on a 30A fuse , now a 32A breaker, served 1000 sq feet (call it 100 sqm)  now in 2.5mm cable, in the past an imperial equivalent
    2. A  30 A radial served 700sq feet or 75sqm now in 4mm cable, in the past an imperial equivalent
    3. the 2.5mmsq radial serving  400sq feet or 50sqm , originally on a 15/20A fuse wire and now on a 20A breaker.
       

    I was never really sure why the two 30 A cases were not the same area- perhaps an assumption about the building shape and circuit styles- radials for long thin buildings maybe, in any case these are no longer how we do things,  but the figures are retained as a rule of thumb that may serve to guide or as a starting point in cases of uncertainty.

    (not enforcing it however  also sidesteps silly questions like does adding a garden socket for the lawnmower increase the area served by the area of the lawn..)

    A radial does not need to be end fed, it can be centre fed (so 2 wires at the consumer unit) and can have as many branches as you like, but to do so  makes it harder to test. Note that most sockets are pretty full/ inadequate with 3 cables of 4mmsq.

    Mike.

     

     

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  • 0

    Further to that, in the days when pipe smoke was popular, and loads were calculated on floor areas served,  we had 3 ‘standard circuit’ choices that allowed an unlimited number of 13A sockets these were  

    1. A ring on a 30A fuse , now a 32A breaker, served 1000 sq feet (call it 100 sqm)  now in 2.5mm cable, in the past an imperial equivalent
    2. A  30 A radial served 700sq feet or 75sqm now in 4mm cable, in the past an imperial equivalent
    3. the 2.5mmsq radial serving  400sq feet or 50sqm , originally on a 15/20A fuse wire and now on a 20A breaker.
       

    I was never really sure why the two 30 A cases were not the same area- perhaps an assumption about the building shape and circuit styles- radials for long thin buildings maybe, in any case these are no longer how we do things,  but the figures are retained as a rule of thumb that may serve to guide or as a starting point in cases of uncertainty.

    (not enforcing it however  also sidesteps silly questions like does adding a garden socket for the lawnmower increase the area served by the area of the lawn..)

    A radial does not need to be end fed, it can be centre fed (so 2 wires at the consumer unit) and can have as many branches as you like, but to do so  makes it harder to test. Note that most sockets are pretty full/ inadequate with 3 cables of 4mmsq.

    Mike.

     

     

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