I the situation I am describing final circuits are leaving the customers property and going into common areas.

I'd suggest that from the "common property"'s point of view it's a similar problem - having multiple sources.

Circuits leaving the original "property" aren't unknown either (depending on what you define as the property) - obviously outside lights and garden circuits leave the main building, similarly supplies to outbuildings aren't uncommon, even if that other building is rented out or even is owned by someone else (where's there's some private arrangement to pay for the electricity used). At home I have my own supply to a street lighting column - which most casual observers might thing was well outside of my curtilage but due to the obscure local arrangement of unadopted roads is actually on my land, so for anyone without access to my deeds, would certainly appear to be 'exported'. (It it labelled inside so it's clear where the supply comes from if anyone takes the outer cover off).

   - Andy.

AJJewsbury said:

I have my own supply to a street lighting column

How quaint! Isn't it more traditional to go the other way? :-)

Thanks for your reply, The Property is a block of flats there is one three phase landlord supply which serves a lift, close lighting and external lighting on the surrounding land to the boundary of the plot, There are six individual metered DNO domestic single phase supplies one in each tenants property.

It is my view that single phase 230V LV final circuits from the tenants consumer unit only serve equipment within that individual flats and that 400 / 230 LV final circuits from the landlords supply only serve equipment located in the common areas. In the situation I am dealing with there is a proposal to bundle final circuits from all installations in a single location

Hi Alan

Could you use

Alan Gray said:

400 / 230 LV final circuits from the landlords supply

to power the ASHP.  Then meter it back to the tenants?  I would also consider the Landlords supply be specified with a design consideration for EVSE.  This could help resolve the issue of differents supply in one external location with possible different CPC/Earth.

Next part of the puzzle will need to be some kind of RF to control the ASHP from within the flat. 

Alan Gray said:

In the situation I am dealing with there is a proposal to bundle final circuits from all installations in a single location

That is more worrying. I had assumed that the cables to each unit would run separately, but if by "bundle" you mean place in the same containment system, there is indeed a problem.

I think at the least it needs a policy of one flat, one electrical box, one isolator, all clearly labelled up and separated, even if in the same outbuilding.

At best it will end up looking like one of those basements you get in small blocks of flats where all the meters and sub-mains converge.

Mike