Extending Meter Tails

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Hi
 
Just some background, I fast-tracked into being an electrician a few years ago and doing ok, however, the practical options for the following has been the interesting bit. Grateful for any thoughts...
 
Scenario:
Customer has an external flush meter box on the side of an attached garage. CU is internal about 1m above external meter. Supply is TNS, 80A
 
Customer is converting garage to a dining room and extending upwards and to the rear with a kitchen. CU to be moved to the kitchen (still on the same wall as the meter box). This will mean a horizontal distance of about 8 metres.
 
Question is how to extend the tails from the meter box to the new CU ( FYI: Customer does not want to have SWA on the outside and no obvious electrical hardware etc  in the dining room) .
 
 
 
I appreciate when it comes to costs and practicality it may be external SWA but until then..... 
 
My thoughts so far for a viable option????
1) Run the existing tails into a new external box (sitting above the current meter box) with a fused (60A) isolator
2) Using Split Concentric Cable (25mm CSA for L,N&E), Run horizontally out the rear into 25mm steel conduit and up a chase on the the inside wall. I would also have a double socket placed below the vertical chase as a belt and braces approach to prevent damage i.e the chase will then also be in a valid zone.
3) Run the Split Concentric Cable out from the wall into the new ceiling joists , through the joists to the kitchen area.
4)  In the new kitchen area, run down the wall in 25mm steel conduit and terminate in new CU.
 
So, opening myself up to any constructive thoughts...
 
  • Does this seem a practical approach?
  • I haven't used Split Concentric Cable but I understand it will run in 25mm conduit however terminating can be interesting? Thoughts?
  • I need a small external recessed box to house the fused isolator but cannot find a smaller one other than a meter box) (local wholesalers drew a blank)?
 
Thanks in advance. 
 
 
couldnt they just move the existing CU to high level and put a cabinet round it?

how do you plan on jointing all those cables without anything 'obviously electrical' being visible ?

 
install isolator next to meter. then tails through wall and up above ceiling, along to new DB then drop down. put a steel plate (note, thats a steel palte, not capping) over the cable for mechanical protection. done.

and then allt he other cables to be moved...

 
Last edited by a moderator:
Put external box to house switch fuse isolator. Knock hole at high level above new box between joists, fish cable cable upto hole then across/through joists to new position, knock another hole between joist at new position and a joke at height of cu then fish cable through top out of lower hole, simples!

 
Why are you fitting a 60a sw fuse when the supply is 80a......or has Mr Merlot been staying with me for too long?
Cue the discrimination comments I'll bet!

No point in derating the available supply with the 60A sw fuse IMO.

(Could just be the Lindeman's Tollana Shiraz Cabernet Sauvignon 2012 talking........... :Y )

 
I thought that there was something in the red or green about split con, but I can't find it.

However, you cannot treat as swa, you have to treat as flex as it does not have an earthed outer protection anyway, as you have an insulated & sheathed live conductor wrapped around the inner core.

So, you would have to protect the splitcon with a 30mA RCD.

You could always go the MICC route, that would be much less obtrusive & not need an RCD, as the outer would be earthed.

Going on manufacturers data 10mm sq MICC sheathed is good for 88A, less in BS7671, but you can use manuf'data, but you would have to confirm rating according to installation method, and it is less than 15mm diameter for a 2 core.

If you have to go to 16mm sq it is only just over 16mm dia.

Easier to hide due to size, if you got it unsheathed then it would be smaller again.

Earthed outer, so no RCD required if buried also.

 
I thought split con could be used in domestic in earthen galvanized trunking? Anyhow micc seems the best solution if you can find 8m of 10mm.

Is it worth future proofing incase they want to add a bathroom above the dining room and want an e shower?

 
Hi Guys

Many thanks for the feedback. As ever the cat has been skinned many ways. A couple of points below:

1) If I needed a small external recessed box (as a meter size box will be ridiculously large) to house a fused isolator  (local wholesalers drew a blank)?

Any thoughts who does one?

2) Following the Forum Feedbacks :

a) Didn't we settle on the fact that we can't use split concentric under 7671 as it has no armouring . ?

b) I was told last millenia by NICCY that Split Con could not be used except by DNO due to lack of circumferential armoured protection

c) So, you would have to protect the splitcon with a 30mA RCD.

My Response:

Due to the run in a wall chase via 25mm steel conduit and no additional protection when running between joists >50mm from surface (i.e. floor and ceiling) so I did not see a need for cable armour (i.e.SWA) or RCD protection (Correct me if wrong!)

Thanks again for you help

 
2) Following the Forum Feedbacks :

a) Didn't we settle on the fact that we can't use split concentric under 7671 as it has no armouring . ?

b) I was told last millenia by NICCY that Split Con could not be used except by DNO due to lack of circumferential armoured protection

c) So, you would have to protect the splitcon with a 30mA RCD.
if you cant use split con because it has no armouring, then by that logic you cant use T&E either. or flex. or DI tails. or any other cable without an armouring

split con can and is used for fixed wiring, but like i said above, its treat the same as T&E for mechanical protection

 
Hi Guys

Many thanks for the feedback. As ever the cat has been skinned many ways. A couple of points below:

1) If I needed a small external recessed box (as a meter size box will be ridiculously large) to house a fused isolator  (local wholesalers drew a blank)?

Any thoughts who does one?

2) Following the Forum Feedbacks :

a) Didn't we settle on the fact that we can't use split concentric under 7671 as it has no armouring . ?

b) I was told last millenia by NICCY that Split Con could not be used except by DNO due to lack of circumferential armoured protection

c) So, you would have to protect the splitcon with a 30mA RCD.

My Response:

Due to the run in a wall chase via 25mm steel conduit and no additional protection when running between joists >50mm from surface (i.e. floor and ceiling) so I did not see a need for cable armour (i.e.SWA) or RCD protection (Correct me if wrong!)

Thanks again for you help
1)

4 or 5 of my local wholesalers do, and 2 of them would be nationals, also try cpc, Farnell, & RS if you are stuck, maybe even Maplin.

2)

Not quite, you CAN use splitcon, but it must be treated as flex as it does not have an earthed outer, as the N conductor is only insulated & sheathed.

As I have said above you would have to protect the splitcon as a flex, and if a flex (or flat twin & cpc) needed RCD protection then the splitcon would also.

Seriously unless you can arrange earthed mechanical protection that is out of sight to meet the client requirements then MICC is probably your best bet, just make sure you make it off correctly.

 
Trouble with MICC is buying a short length unless you had some in stock , I'm guessing @ 50mts min  plus terms. 

I think we missed the fact that he's installing 25mm steel conduit so he,s good to go with the split con.

25mm steel conduit on domestic ! 

Have to say if it were my job I'd just tell him the regs don't allow the cable on the inside so its an SWA up the outer wall and through the ceiling joists .

If the DNO were doing it they'd just clip along the wall outside and everyone would accept it.

I had a customer once who put that many restrictions in our way regarding , don't want that there , can we have that over  there , I don't want to see this , I don't want to see that I went home before he got in from work & let him waste the builder's time , then gave builder quotes for all the Part Peeing about  .

It stopped after that .

 
Am I missing something here or wouldn't it be easier and less hassle to run the SWA in like he's proposed to do with the split con and galv conduit as as long as it's made off right and the armoureds earthed then everyone's happy, cheaper than pyro and quicker than messing on with 25mm galv 

you could even make the DB end off into a galv end box set back into the wall to get a sound termination and earth from that aswell

oh and as for the meter end is there no room for an isolator in the meter box??? CEF sell a nice slimline metal clad isolator that you could squeeze in there 

 
I did say that Sidey , :innocent   I thought  a metalclad Sw/fuse  , gland the SWA , but could bring it into an insulated board , just strip it back , clip it to the back of the board. 

Or fit a metalclad board too. 

 
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