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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!

Parents
  • 0

    Basing things on circuits when the circuits are over-sized for the actual application will naturally give over the top results - e.g 20+20+32A = 72A  could serve a floor area of around 240m² - over two normal size houses. Ditto 6A circuits for a could of hundred watts of LED lighting. If you want to do it circuit wise (there are other methods) then base it on the minimum size/number of circuits that could have been installed to serve the actual loads. We're only worried about maximum demand at this point, not minimising inconvenience or optimising cable runs.

    What's the nature of the "25A or 61A heating" - is it off peak or 24h space heating? - 14kW feels rather a lot for heating even a fairly poorly insulated house if it could be on constantly.

       - Andy.

Reply
  • 0

    Basing things on circuits when the circuits are over-sized for the actual application will naturally give over the top results - e.g 20+20+32A = 72A  could serve a floor area of around 240m² - over two normal size houses. Ditto 6A circuits for a could of hundred watts of LED lighting. If you want to do it circuit wise (there are other methods) then base it on the minimum size/number of circuits that could have been installed to serve the actual loads. We're only worried about maximum demand at this point, not minimising inconvenience or optimising cable runs.

    What's the nature of the "25A or 61A heating" - is it off peak or 24h space heating? - 14kW feels rather a lot for heating even a fairly poorly insulated house if it could be on constantly.

       - Andy.

Children
  • 0 in reply to AJJewsbury

    Yeah minimum circuits it a good way to do it sensibly. The heaters will be oil filled electric radiators, about 8 of them around the house, either 800W or 2kW each (hasn't been decided yet). Worst case scenario but my main concern is if its cold in winter and the electric heating radiators are all put on (25A or 60A), then you have a shower (44A), someone is in the kitchen cooking (17.5A) and uses the hot tap to wash up (24A).

  • 0 in reply to AJJewsbury

    Also thanks for the minimum circuit tip, do you mind saying the other method of calculating maximum demand you mentioned or what you usually use?

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