extending a sub main

[tbs1983]

hi guys, I have a job in a flat where a wall is being removed to make it open plan, the wall contains a 10mm T&E sub main that feeds the DB for the flat.
In order to re-route the sub main, I will have to extend it very slightly (2m max), I'm unable to run a whole new sub main due to routes/logistics just not possible.

What is the best way to extend the cable bearing in mind it may be carrying 50A or more.
I have seen large coffin junction boxes but am not overly keen on the idea of using a JB for this purpose bearing in mind the load it may have to carry.
Any better suggestions? thanks in advance

 

[GLENNSPARK]

just a thought here...

as you will be extending and thus modifying the circuit then if its to be buried within the wall it will either need additional/fault protection by means of 30mA RCD top end..
or running within an earthed metallic enclosure...such as a conduit or trunking...

go for an armoured re-feed if you can....

 

[ExArmy]

if the new cable is not going to be chased in (i.e under the floor, above the ceiling, in a stud wall deeper than 50mm) then i'd just through crimp and extend it.

 

[Engineer54]

hi guys, I have a job in a flat where a wall is being removed to make it open plan, the wall contains a 10mm T&E sub main that feeds the DB for the flat.
In order to re-route the sub main, I will have to extend it very slightly (2m max), I'm unable to run a whole new sub main due to routes/logistics just not possible.

What is the best way to extend the cable bearing in mind it may be carrying 50A or more.
I have seen large coffin junction boxes but am not overly keen on the idea of using a JB for this purpose bearing in mind the load it may have to carry.
Any better suggestions? thanks in advance

Where are you intending to make the extension joint to this flat's supply cable, ...under the floorboards, buried in a wall, or where??

 

[GLENNSPARK]

Where are you intending to make the extension joint to this flat's supply cable, ...under the floorboards, buried in a wall, or where??

exactly...

 

[GLENNSPARK]

has the O/P carried out any investigative work as to a new cable run?

or just assumed it cant be done..?

and before the old cost card gets played...then he should have taken this into consideration ...before pricing..

 

[dazza1981]

I was thinking the same.....it would need to be accessible if you do end up joining it, although i would only do that as an absolute last resort and run a new armoured supply if you can.

 

[tbs1983]

thanks for replies guys, joint would be under a floorboard therefore deemed accessible, sub main will be RCD protected. just looking for advice on the best possible way i can carry out this joint as new sub is out of the question (we have explored the idea thouroughly!!!)

 

[davethsparky]

Don't forget you can't have the whole flat protected by the same RCD.

 

[dazza1981]

What rating is the rcd?

 

[tbs1983]

split CU in flat dave, just looking for some advice on best or safest way to create the cable joint if anyone could advise. Rest of installation is all in hand and will be carried out to BS7671 (17th ed) !!!

 

[tbs1983]

100mA at source and 2 x 30mA in CU Dazza.

 

[davethsparky]

But you just said the sub-main will have an RCD on it? Therefore it will have one RCD covering the whole installation!

 

[Sintra]

thanks for replies guys, joint would be under a floorboard therefore deemed accessible, sub main will be RCD protected. just looking for advice on the best possible way i can carry out this joint as new sub is out of the question (we have explored the idea thouroughly!!!)

split CU in flat dave, just looking for some advice on best or safest way to create the cable joint if anyone could advise. Rest of installation is all in hand and will be carried out to BS7671 (17th ed) !!!

Can't have 2 30mA RCD's in series either.

 

[davethsparky]

100mA at source and 2 x 30mA in CU Dazza.

Then you need to add mechanical protection to the submain where it is buried as it would have to be protected by a 30mA RCD and be in the safe zones to allow this to be omitted.