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2 phase DB - allowed?

vantech

Hi, 

Planning a domestic upgrade to a 3 phase supply for the purpose of having a 22kW EV charger and an ASHP. 

To balance the phases correctly, the current EV charger supply could be utilised to feed a new DB inside of the property. The cable is a 10mm2 4 core armoured. 

Could this cable be utilised as a feed to a new DB, as follows: 

L1 

L2 

N

Earth 

We would essentially then have a 2 phase DB, rather than 3 phase. I haven’t seen a setup like this before but presume it’s ok? The DNO intake is next to the EV charger, so a small 3 phase board outside, could supply the new EV charger with a separate 2 pole / 2 phase breaker dedicated to the new indoor DB.

The existing DB would remain as is, with some circuits moved across to the new 2 phase DB. 

Any ideas / comments?

Thanks. 

Parents
  • 0

    Interesting idea!

    I think that you would want a 3-phase MCB for the distribution circuits. AFAIK, there is no obligation to connect circuits to all of the outgoing terminals. After all, at any one time, one out of three phases may be drawing no current.

    I am not sure that the phases need to be balanced so long as there is a full-size neutral.

  • 0 in reply to Chris Pearson

    Thanks. 

    The 10mm feed could be protected by a 50A 2 pole MCB, and within the new DB, the line conductors and neutral through a 3 pole main switch for complete isolation? 

    https://www.cef.co.uk/catalogue/products/40889-50a-dp-10ka-type-b-mcb

    A 3 pole switch in the DNO cupboard provides a single point of isolation for the new and existing DB. 

Reply Children
  • 0 in reply to vantech

    So if you put a 2 pole MCB in the 3 phase board, will you just blank off the 3rd phase? You might as well put in a 3 phase MCB.

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