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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

    The question though, if this was your job, would you be upgrading to 3 phase or do you think single phase 100A will be safe with these kind of loads?

    You're asking the wrong person there - if it were mine I'd spend the money on upgrading the insulation rather than the electricity supply - and so cut down drastically the space heating demand. (50mm PIR is a bit thin for a loft - roughly that's 100mm rockwool equivalent - even the current building regs ask for about 3x that IIRC). For hot water I'd likely go for an immersion setup - you can have mains pressure still (e.g. megaflow type setup), better flow rates, lower rated circuit (so lower max demand) and the option of using cheaper off-peak tariffs to do the bulk of the heating. Likewise I'd look carefully at storage heaters to be able to use off-peak for the bulk of the heating, or even heat pump(s). kW for kW electricity is several times more expensive than gas.

       - Andy.

  • 0 in reply to AJJewsbury

    Thanks, I'll look into it. What if the loads I mentioned were specified and you 'had' to install them. Would you keep a single phase 100A supply or suggest an upgrade to 3 phase?

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