how to use an extra phase

A three phase smart meter should be able to accomodate split phase.  there will just be unused terminals.  Split phase is really quite common in rural areas.  Tell them to send a three phase approved installer though.  If the cutouts are a problem then UKPN should change them FoC.  Why not post a picture here.

Humm Thanks - that seems to answer most of the questions. No obvious reasons why not to my eyes.

The cut-out looks to be an older type - the fuse carriers look somewhat short to me - I wonder if they take a different kind of fuse they don't carry any more?

   - Andy.

Hmm, well as far as I can see, there is nothing obviously terrible about that incomer and fuses, apart perhaps from the TNS to TNC-s conversion at some point in the past, which may hide a latent Zs issue or PILC problems to come. But that would be a DNO matter, and by the sounds of it they are happy. The incomer looks like it is one that could have been configured for  3 phase, as the right most slot (normally neutral) seems unused, but again that is not really a show stopper, any more than the few single phase incomers that have live on the right, they all need checking before connection anyway.

It is unusual to have things wired for 2 phases and not 1  or  3, but as others have said, far from unknown, especially  in slightly larger buildings or ones that have been shops with a flat above in the past.  A normal  3 phase whole-current meter will read just fine, simply recording zeros for the dead phase, just as it would if one fuse had gone,

For some reason they don't want to do it, or to send someone with the right kit Quite why is unclear, as from that photo it should be straightforward.

Mike.

Hmm, well as far as I can see, there is nothing obviously terrible about that incomer and fuses, apart perhaps from the TNS to TNC-s conversion at some point in the past, which may hide a latent Zs issue or PILC problems to come. But that would be a DNO matter, and by the sounds of it they are happy. The incomer looks like it is one that could have been configured for  3 phase, as the right most slot (normally neutral) seems unused, but again that is not really a show stopper, any more than the few single phase incomers that have live on the right, they all need checking before connection anyway.

It is unusual to have things wired for 2 phases and not 1  or  3, but as others have said, far from unknown, especially  in slightly larger buildings or ones that have been shops with a flat above in the past.  A normal  3 phase whole-current meter will read just fine, simply recording zeros for the dead phase, just as it would if one fuse had gone,

For some reason they don't want to do it, or to send someone with the right kit Quite why is unclear, as from that photo it should be straightforward.

Mike.

It is unusual to have things wired for 2 phases and not 1  or  3

I've a feeling it's more common in areas that originally has d.c. supplies - original 3-core cable carried +/0/- so conversion to a.c. meant they were one core short for proper 3-phase (at least if not doing TN-C, which they didn't in those days).

  - Andy.

I agree with Andy and Mike.

There is certainly no need to balance the phases - any suggestion that the highest phase consumption is multiplied by three is no more than a rumour.

Naturally, a 3-phase meter will be a bit wider, so may not fit on that board.

Yes, and also for that same 3 core DC mains reason I have been told that there are parts of the old Eastern Power  London region that only have 2 phases in any one street, just rotating which 2 of the 3 phases per street to balance the transformer loading over all 3. Its the sort of thing that you might think would have changed by now, as London was one of the first areas to move to AC pre-war but in practice it is so over-built that cable replacement are only done where unavoidable.

Mike.