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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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    And of course the DNO sizes the transformer/ substation on about 4 amps per house, because so long as there are enough houses in the street that so that one is off when others are on, that total 'after diversity maximum demand'  is unlikely to be exceeded long enough to set fire to anything - though it must be noted that short term (less than an hour) 100% overload (i.e. twice design current) is not totally unknown in some 'hotspots' .
    Of course if in future lots of houses have cars to charge or install heating like this, then the picture changes a lot and assumptions may need revision.
    Mike

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  • 0

    And of course the DNO sizes the transformer/ substation on about 4 amps per house, because so long as there are enough houses in the street that so that one is off when others are on, that total 'after diversity maximum demand'  is unlikely to be exceeded long enough to set fire to anything - though it must be noted that short term (less than an hour) 100% overload (i.e. twice design current) is not totally unknown in some 'hotspots' .
    Of course if in future lots of houses have cars to charge or install heating like this, then the picture changes a lot and assumptions may need revision.
    Mike

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