concentric cable submain

[kevben]

just quoting on a job which involves some alterations.

the property is a new build block of 12 x flats (2008), each supplied with 16mm concentric cable, 60A Main switch fuse at meter position, no RCD protection and unsure on installation method etc.
The property will be converted to a 'care in the community' property, with a new office built (taken from a top floor flat), which will require a sub-supply/sub-main to provide power to lighting,sockets,panel heater & shower.
I would prefer to install a new supply but the cable run is very long & difficult.
We have the easy option of 'tapping' off the converted flat & installing a sub-meter.
We are planning on replacing the Consumer Units (16th - 17th) & installing emergency lighting for each flat.
I've not worked with concentric cable before & would appreciate any advice regarding this particular matter plus the fact the sub-mains have no RCD protion.
cheers

 

[Knobhead]

Get the correct heat shrink boots and tube to terminate them. Otherwise in E54’s immortal words it will “look like a dogs dinner”.

 

[Fin170]

We are planning on replacing the Consumer Units (16th - 17th) & installing

Replacing what with what?

I'm assuming you mean providing better discrimination & additional protection to the existing units with ~2 RCBOs? :lol:


As for the concentric, I'd try and find out where it's run. But if it's likely it's run through communal areas, maintenance/staff rooms etc then you could argue the under professional/ trained staff bit and not need it. Being it's a flat for the elderly I'd try and avoid a RCD on the sub main, if that goes it could be very awkward for a elderly resident to re-set it.....it's bad enough trying to get access to such things as the person working on them sometimes

 

[malcolmsanford]

let page 4 of the regs and the introduction to it be your guide here.

Paraphrase as

" Existing installations that have been installed in accordance with earlier editions of the Regulations may not comply with this edition in every respect. This does not necessarily mean that they are unsafe for continued use or need upgrading"

The part highlighted in bold is the main part here. As long as your work that you undertake is to the current standard of the regulations ie the tap off part, fitting the new CU etc then the way it is fed, ie by the sub main to the 16th edition should not be an issue

If you wanted to fit an extra socket off of a RFC and you buried the cable as per normal, then you are quite entitled by the regulations to just have your one socket and cable RCD protected, the remainder of the RFC does not need to be.

Though in this scenario I always felt what is the point of having say 10 sockets non RCD protected and your single one RCD protected and so a pretty poor reg, in your scenario it will allow you to make that call as per regulation 522.6.101

 

[Engineer54]

Get the correct heat shrink boots and tube to terminate them. Otherwise in E54’s immortal words it will “look like a dogs dinner”.

Think that should be ''look like a Pigs Ear'' ... lol!!!