3 phase supply - new dist board?

Discussion in 'Electricians' Talk' started by The Biochemist, Sep 13, 2021.

  1. The Biochemist

    The Biochemist New Member


    Not an electrician but just want some advice about which electrician seems to make most sense before I go with them.

    Situation is I would like to have installed a 3 phase ev charger at my business premises.

    Currently it has a standard domestic single phase supply and a standard simple distribution board.

    Assuming dno will install a 3 phase supply and I can get my electricity provider to meter/charge or what they need to do...

    Electrician 1 says we could keep the existing single phase dist panel as is and 'feed it' from one of the phases. Then separately connect the 3 phase ev charger across the 3 phases as necessary.

    Electrician 2 says that the existing dist panel needs to be removed and a new 3 phase panel added with the various loads 'balanced' across the phases including the 3 phase ev charger .

    Clearly they have a more technical view of what they intend to do but that is how they explained it to me.

    Cost differential is material between the two so advice on the most common sense and safe approach would be much appreciated.

    Note, minimal existing significant loads eg...

    Washer dryer

    Then the usual insignificant loads like fridge/freezer/gas water heater and heating/3 pcs/ 20 led lights/etc...

    The ev charger is likely to be 11kw or 22kw depending on supply capacity.
  2. Tony Goddard

    Tony Goddard Screwfix Select

    Electrician 1 I would suggest is a domestic sparky in the main, not used to 3 phase, his approach would work but leave the supply inbalanced, which is poor practice at best.

    Electrician 2 is (in my opinion as a commercial spark) on the money, his approach will not only give you a neatly balanced system, it should also be physically slick (ie DNO equipment feeding into a nice tidy single DB).

    Electrician 2 will cost more, the 3 phase DB alone is a cost, but consider these lines by john Ruskin

    "There is hardly anything in the world that cannot be made a little worse and sold a little cheaper, and those who consider price alone are that man's lawful prey.

    It's unwise to pay too much, but it's worse to pay too little. When you pay too much, you lose a little money - that's all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the thing it was bought to do. The common law of business balance prohibits paying a little and getting a lot - it can't be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better."
    Fusebox Wales likes this.
  3. techie

    techie Active Member

    What Tony said…
  4. MGW

    MGW Screwfix Select

    Amps used by domestic will be taken off supply amps to see size of EV charging point, is domestic split total amps will be less, so larger charging point may be possible, but until you know figures it can't be worked out.

    Safer if domestic single phase, but likely larger charge point possible with 3 phase.
  5. Comlec

    Comlec Screwfix Select

  6. The Biochemist

    The Biochemist New Member

    Thanks Tony

    Both spoke with seeming authority so very helpful for a sense check. I really appreciate you giving me a straight answer and not some flippant response, it is difficult to know what to do when two people are giving logical arguments but polar opposites of each other.

    Wholly agree with the pay what is right for the right job; not wanting to scrimp but also not wanting to be sold something unnecessary.
  7. Tony Goddard

    Tony Goddard Screwfix Select

    No problem, glad to help, I would go with option 2 (three phase DB) without hesitation, and would not have offered the first option myself.

    Enjoy driving your new EV, thinking of going electric myself!
    Starslikedust likes this.

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