8 metre meter tails

You do not mention CPC, but I assume there is one.?

If these tails are to be protected only by the DNO fuse, then you need their buy in to that, even if they are after the meter. However I presume there is a switch fuse per flat near the metering, and if there is then downstream you can do what you like really. I have seen T and E in this situation, but the reduced earth is a bit of a pain, singles in conduit are a better choice.

Hello Thanks for the reply, at the moment there's 3 DNO 100A cut outs ( no seals) and 3 meters, 2 of which are to lashed up boards for working power but no switched fuses. Certainly am going the singles route, I've spent enough time working to get marginal disconnection times legitimate (pretty much go straight to dropping the circuit rating now)

You cannot have 8m meter tails.


Where are the meters at the origin or in the flats?

Hello John,

Apologies for the late reply. The meters and cutouts are all in the same position, one cupboard in the central flat currently being renovated. The developer wants to leave them there and extend through the conduit to CU's in the next flats,(which he'll rent out).

Peter

So yes, at the origin, and it's not possible to install an 80A switched fuse after the cutouts to protect the run to the the CU?

Thanks for your time

So it's starting to sound like this is really just a consumer-side distribution circuit, supplied by a switchfuse next to the meter, rather than meter tails in the conventional sense.


I'm not seeing any need for 'Scottish power red' for the conduit. I'm presuming this is PVC conduit rather than steel?


How is the conduit getting to/from the ceiling void? You mention of correct zones makes me suspicious that it might be concealed in a wall. If it is and it's insulating conduit then there might be the additional protection by 30mA RCD requirement to consider.


   - Andy.

Hi Andy,

Yes, I confused the issue with  'meter tails' but it's certainly the (TBC 25mm) line,neutral & CPC between the switched fuse,/8 metres/CU.

I'd anticipated running up in conduit on the outside of the wall in the cupboard into the ceiling void and continuing in conduit the 8 metres run through to the next flat. Staying in conduit on ext. of wall there straight to the new CU. 

Scottish Power Red not a regular SI unit I know...its a 5mm wall I think and yes PVC,

Thanks,

Peter

For the avoidance of a 30mA  RCD in a silly place, assuming not TT supply, then  metal trunk (2 by 2 inch or so should do it) may be a more forgiving choice of enclosure, as you can earth the trunking, and do not have to bury it so deep into the walls. (even then TT and a 100mA slow RCD and then trunking is an option that is less trippy than 30mA at origin, especially as resetting could mean going into another flat by the sound of it  which does not sound sensible.)

And if the meters go to a switch fuse per flat, even with the same fuse rating as the DNO fuse, you can then say 'there ends the DNO fuse responsibility' and do what you like after that without the DNO getting too fussy, and it is a jolly good idea for maintenance and/or if one flat falls vacant and needs to be isolated leaving the rest of the building on.

I don’t like the idea of supplying flats from a central source in another flat. I can see issues with fire compartmentation.

I can't help thinking that SWA will be easier than drawing 25mm² into conduit. Using 3-core (one core for c.p.c. in parallel with the armour) should give you as good if not better Zs results than singles in plastic conduit too. With a steel CU and steel switchfuse, glanding off the SWA would be straightforward too.

   - Andy.