Extending sub main

[Yellowhammer]

Hello,

Planning some work for someone currently installing a new CU and a switch fuse in an extension, fed from a new DNO supply. Have turned up and had a look at it, mostly seems all okay other than the hockey stick being on the wrong side of the meter box.

However, the 63A switch fuse is for an annexe down the garden which I've had nothing to do with. Arrived to find a 16mm and a 6mm NYJJ buried ducting running from this building, and a garage to the new CU position, but both are lovely and short at both ends. Only about 500mm out of the floor currently. My suggestion around re-pulling a longer length was not met with any smiles or enthusiasm, understandably.

Tails are planned to come through the wall from the meter, up the wall into the board and the switch fuse, with a 3mm steel plate over them between entry to the building and the CU. The wall is being studded and boarded so there is some space to fit this all in.

Ideally I would run the NY behind this plate too, giving it suitable mechanical impact protection within the wall, however the shortness has buggered it up. Considered terminating into a box at low level and extending up, but it's messy and 63A rated terminations aren't small. (Also having 63A connections surface at that sort of level isn't something I'm wild about, if someone sticks a desk on the wall and breaks the box or something, it's not ideal. I'm contemplating using a torpedo to extend it in the wall, but it's not sitting well with me..

Any opinions on doing so, or alternatives? Would comply with 526.3, but just doesn't feel very nice at all (to me, at least).

 

[UNG]

My alternative would be walk away which is what I think someone else has done

 

[snowhead]

What about a recessed wall box for the joint (not a meter box)

There are all sorts of sizes available from different manufacturers,,

48 Range Flush-mounting junction and modular boxes range | Gewiss

The system is composed of three ranges: 48 PT / 48 PT DIN Range with moulded DIN rail, compliant to CEI 23-48, suitable to install also H&B devices;...

www.gewiss.com

 

[timhoward]

I'm not immediately baulking at the resin joint idea. If done right (crimped) it should be trouble free forever, after all they are normally buried for decades! It's then effectively the same cable and should fit behind the 3mm plate.

 

[mainline]

If the torpedo is achievable then that would be my choice, as Howard said, as long as you can be assured of solid connections within the torpedo.

 

[Yellowhammer]

My alternative would be walk away which is what I think someone else has done

I can completely see this, however the guys a nice bloke and father of a friend. I'd like to sort it out for him properly rather than just leave him high and dry and at the mercy of someone who might just rough it in.

What about a recessed wall box for the joint (not a meter box)

There are all sorts of sizes available from different manufacturers,,

48 Range Flush-mounting junction and modular boxes range | Gewiss

The system is composed of three ranges: 48 PT / 48 PT DIN Range with moulded DIN rail, compliant to CEI 23-48, suitable to install also H&B devices;...

www.gewiss.com

This is a nice solution, will definitely explore further, thanks!

I'm not immediately baulking at the resin joint idea. If done right (crimped) it should be trouble free forever, after all they are normally buried for decades! It's then effectively the same cable and should fit behind the 3mm plate.

Definitely crimped, briefly looked at the wiska pre gelled things and swiftly wrote them off given they come with screw terminals. Oddly CEF say they're rated for direct burial, but the wiska datasheet makes absolutely no reference to it.

This was my dilemma, I don't necessarily see an issue with it, fairly happy it's fine from a regs perspective, and longevity, it just feels less than perfect. Such is the way with these things sometimes, perhaps.

If the torpedo is achievable then that would be my choice, as Howard said, as long as you can be assured of solid connections within the torpedo.

Thanks, this is reassuring!

 

[KungFuTurkeyLeg]

If it's buried ducting, have you thought about digging up a section of the buried cable close by, cutting it and pulling in a few extra meters inside with the torpedo outside?