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3 phase supply upgrade required?

Jimi

Do you think the following installation would require a 3 phase supply upgrade? Here are the calculations based on the on site guide maximum demand table:

6A lights down – 66% = 4A.
6A lights up – 66% = 4A.
6A smokes – N/A.
20A sockets down – 40% of others = 8A.
20A sockets up – 40% of others = 8A.
32A sockets kitchen – 100% of largest = 32A.
32A oven and hob – 10A + 30% remaining (35A – 10A = 25A * 0.3 = 7.5A + 10A) = 17.5A.
45A water heater 1 (10.1kW) – 100% of largest = 44A.
25A water heater 2 (5.4kW) – 100% of second largest = 24A.
32A garage – 1 rad (9A), sockets (40% of others = 8A), lights (66% = 4A) = 21A.
25A or 61A heating – no diversity allowed = 25A or 61A.

Total = 188A or 224A (depending on electric radiator choice).

If the table was used seriously for every installation then nearly every house would be over the 100A standard, don't you think? But this is an all electric system so is particularly demanding of energy.

Thanks!

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  • 0

    Careful you don’t end up with this when someone rather oddly elected to go for E7 heating in an unoccupied dwelling, which has some historical significance! 


    All four transformers serve the dwelling which has four separate single-phase supplies made common at an adapted busbar chamber.

  • 0 in reply to lyledunn

    All four transformers serve the dwelling..

    Well that is pretty unusual.
    Well in this case the DNO could not easily do 3 phase, as the HV side only has 2 wires, and unless the 3rd HV phase is quite close then adding the line run afterwards for one building seems a bit much . I cannot help feeling the 4 small pole pigs and what looks like the parallel PME earthing is asking for trouble with any small imperfect matching of impedances and so on. One TX on an H bracket or at least 230-0-230 split phase may have been better, here there is a good chance that the parallel voltages are not perfectly identical. 
    I presume each one is fused at 100A and the total is not bringing any of them near full load.
    Thanks for the pic, that is quite thought provoking, and looks almost as bad as the rural American way of doing 3 phase with different 3 single phase transformers on sponsons hanging off a single pole.

    Mike.

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  • 0 in reply to lyledunn

    All four transformers serve the dwelling..

    Well that is pretty unusual.
    Well in this case the DNO could not easily do 3 phase, as the HV side only has 2 wires, and unless the 3rd HV phase is quite close then adding the line run afterwards for one building seems a bit much . I cannot help feeling the 4 small pole pigs and what looks like the parallel PME earthing is asking for trouble with any small imperfect matching of impedances and so on. One TX on an H bracket or at least 230-0-230 split phase may have been better, here there is a good chance that the parallel voltages are not perfectly identical. 
    I presume each one is fused at 100A and the total is not bringing any of them near full load.
    Thanks for the pic, that is quite thought provoking, and looks almost as bad as the rural American way of doing 3 phase with different 3 single phase transformers on sponsons hanging off a single pole.

    Mike.

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