moving shower?? Can I extend wire

[wozzer438]

I have just changed the layout of my bathroom and need to move the shower unit on to the adjacent wall. I was hoping to feed a new length of cable up through the attic straight to the switch which i have easy access to, however on closer inspection the section of attic I would need to get to, to retrieve the end of the cable is completely inaccessible. The attic is converted and without removing some of the floor and the rear plasterboard walls and skirting boards I have no chance.

My plumber said I could join the existing wiring (6mm) to a new length (6mm) via a junction box and sink the JB in the wall. He advised a 40 Amp JB but I can only find 30 Amp max in my DIY shops. Is the safe and legal? what JB should I use?

 

[ColJack]

this is why plumbers should not give advice on electrics..

YOU CANNOT "SINK A JB INTO A WALL".. it will be inaccessible and it needs to be..

you need to fish in a new cable I'm affraid... so start pulling up those floorboards..

 

[electronicsuk]

That said, as long as you can make the installation comply with a longer length of cable than it was originally designed for, you can make a joint in the wall as long as it remains accessible. A double backbox and blanking plate sunk into the wall would allow you to do this. If the joint is to be in the bathroom itself then it should, as a minimum, be in zone 2 or beyond. However, it's a grey area, as you'd struggle to classify a blank plate as being rated to IP44 or greater. RCD protection would also be required on the cable, if it isn't already present, and you would also need to consult the WIKI on 'safe zones'.

 

[Spark123]

You should also notify this work to your LABC as it is notifiable under Part P of the building Regulations.

What size fuse and what size shower?

 

[Chri5]

1st- A 6mm cable is unlikely to cope with a new shower (esp if over 9 kw).
2nd- RCD protection is mandatory
3rd- If 6mm copes, could you not rerun the feed from the shower switch / ceiling isolation point onward
4th- Notifiable

 

[ColJack]

3RD - that's what he was trying to do.. read the OP more cerefully next time..

 

[sparkysm]

on my recent 17th ed regs course, i asked a similar question about joining cables. and it is perfectly legal and correct to join unaccessible joints but you must use through crimps/lugs. and if in a wall greater than 50mm deep

 

[rebuke]

It is permissible to bury through crimps (although many people, myself included, think it's bad practice), but if doing so you have to comply with 522.6.6, which basically means your cable must either be at >50mm from the surface (not really practical in a house), or be in a safe zone, or be in earthed steel conduit or trunking (i'm assuming here we're talking about T&E so armoured cable etc isn't relevant)...

 

[ban-all-sheds]

on my recent 17th ed regs course, i asked a similar question about joining cables. and it is perfectly legal and correct to join unaccessible joints but you must use through crimps/lugs. and if in a wall greater than 50mm deep

If the person teaching you thought that a joint in a cable imposed a depth requirement all of its very own you should have asked for your money back...

 

[bernardgreen]

however on closer inspection the section of attic I would need to get to, to retrieve the end of the cable is completely inaccessible.

It isn't always necessary to get yourself into the dead space. Pushing loops of string up into the dead space from underneath and then using a hook on a stick to hook the string and pull it between the joists to where you can get to. So if the joists run at a right angle to the wall across the dead space (the rear plasterboard walls) this method may enable you to get a draw cord in to then pull the cable through. With cable that size you need to have one person feeding cable up into the dead space as a second person is pulling it. Trying to pull it round the edge of a hole in plasterboard ceilings is hard pulling, the ceiling may crack at the hole and the cable sheath may get deeply scratched.

The more loops of string pushed up the bigger the target for the hook which makes it more likely to work in a short time. This only requires one floor board to be lifted ( one if you get the right one first time )

 

[Space cat]

In a properly converted attic, there's a good chance that the dwarf walls are sitting on steel beams with new, load-bearing floor joists slung between them. The old ceiling joists will be underneath, either parallel or at right angles. If they're parallel, you'll have a clear run through to the outer wall where I'm guessing that your cable is coming up. If they're at right angles, there should still be a gap where the floor joists cross them. If you measure the thickness of this combination floor and ceiling, you'll get some idea of what's in there.

You can try bernardgreen's string loops but I like to do it the other way. I push a large loop of thin, solid core wire under the floor towards the hole and then try to hook it downwards. The end result is the same.

There's one possible fly in the ointment; loft insulation. If the old stuff (if any!) has been piled up in the dead space, it'll block you either way.

 

[sparkysm]

B.A.S. i was lucky enough to be taught the 17th ed by one of the men responsible for writing the regs book so i will not ask for my money back.

 

[RF Lighting]

Who was that then?

 

[ban-all-sheds]

B.A.S. i was lucky enough to be taught the 17th ed by one of the men responsible for writing the regs book so i will not ask for my money back.

How odd. I wonder why I can't find the regulation that he, or one of his colleagues, wrote which says that if you have a join in a cable in a wall it must be >50mm deep?

 

[securespark]

I can't find the regulation that he, or one of his colleagues, wrote which says that if you have a join in a cable in a wall it must be >50mm deep?

Can you, sparkysm?