Twin Brown + Earth SWA

hesker

Does Twin Brown + Earth SWA cable exist and is it readily available. This is in relation to an external lighting circuit with external switches.

If not what is the practice. Is it acceptable to use Twin & Earth SWA and sleeve over the neutral?

I will be engaging an electrician down the line to do the necessary work for me (including other jobs) but would like to purchase cable in advance.

salmocab

Never came across it, maybe talk to the sparks first as if he rocks up and you have the wrong cable or what he deems wrong then he might just rock back out again

2011

It would be cheaper to allow the electrician to purchase the cable (RECs tend to buy in bulk, get trade discounts and then the lower VAT rate will apply). That way you can be sure that the correct cable is obtained. You may also find that the electrician decides on a different routing resulting in a different quantity of cable required than you thought.

Tuco88

As far as I am aware sleeving is not allowed now. So a way around this was numbered cable cores ie.. a 7 core swa and correctly labelled.

It's rather ott imo.

hesker

OK thanks for input. I'll scout for an electrician so but think it's a bit early.

The situation is that I have an external room/workshop that I'm fitting cladding to. I want a light switch mounted on the cladding. There is a ventilated cavity between the cladding and the timber frame wall. The timber frame wall has a vapour permeable rain barrier on it. I'm worried that if I drill holes to feed cable through after the cladding is up these holes will be a leak path for water so I'd prefer to fit cable now so that I can seal around them.

Does anyone know of a solution to this. Is it possible to get some type of gromett that I can fix on the wall and drill through later for cable fitting.

Tuco88

There is a various types of grommets available.

If he's a tasty electrician he will probably use a PG gland on the cladding.

2011

Tuco88 wrote: »

If he's a tasty electrician he will probably use a PG gland on the cladding.

Exactly.

hesker

Tuco88 wrote: »

There is a various types of grommets available.

If he's a tasty electrician he will probably use a PG gland on the cladding.

PG glands should work nicely. Cheers.

However it does require me to choose the right size gland to fit the cable to be chosen by the electrician. It has to be fitted on the internal wall before the cladding is fitted and I want to get the cladding finished now while weather is good.

hesker

I found a multi-gland product which gives room for some flexibility in cable choice.

And looking at it from another angle I think I can modify one of the cladding timbers to make it removable which would give me complete access.

2011

hesker wrote: »

I found a multi-gland product which gives room for some flexibility in cable choice.

Not suitable.
All stuffing glands work within a range. It will not be difficult to get it right.

hesker

2011 wrote: »

Not suitable.
All stuffing glands work within a range. It will not be difficult to get it right.

Just out of interest why not suitable

2011

hesker wrote: »

Just out of interest why not suitable

That is essentially a gland plate for multiple cables. Installing this would introduce an additional far larger (riskier) point for water ingress.

Remember this only requires on cable, one gland and one gland entry.

hesker

2011 wrote: »

That is essentially a gland plate for multiple cables. Installing this would introduce an additional far larger (riskier) point for water ingress.

Remember this only requires on cable, one gland and one gland entry.

It will be a double gang two way switch for two light circuits so I make it a minimum of 3 cables, but maybe there's a different approach that uses less.

I'm not going to use them in any case as I'm fairly sure I can make one of the timbers removable. However those gland plates are sold as IP66 and probably could be taped to the membrane with membrane tape for added security. You can get them with a lot less glands than shown in the photo.

2011

hesker wrote: »

It will be a double gang two way switch for two light circuits so I make it a minimum of 3 cables, but maybe there's a different approach that uses less.

This does not align with your first post, besides it could still be done with one cable.

If you are planning on using tape to seal the gland plate to the membrane then you are relying on the tape to keep it watertight, in which case why not simply tape around the cables and not bother with the gland plate?

I would leave this to the electrician if I were you.

hesker

2011 wrote: »

This does not align with your first post, besides it could still be done with one cable.

True, but it wasn't particularly relevant to the OP.

2011 wrote: »

If you are planning on using tape to seal the gland plate to the membrane then you are relying on the tape to keep it watertight, in which case why not simply tape around the cables and not bother with the gland plate?

Plates are rated appropriately. Tape is my idea and just extra.
The problem with just taping is how to seal something in a place where you have no access after the cladding is fitted. Taping cables would be fiddly I imagine and easy to leave a leak path. Plus you make cable replacement difficult if it's ever needed.
I am assuming those glands could be punctured during cable fitting and when you pull the cable through it forms a seal around the cable.

I would leave this to the electrician if I were you.

Have posted a request for one. I take the point this stuff is best discussed with the person who's going to do the work. I just thought I could do as much prep work as possible up front.

2011

hesker wrote: »

Plates are rated appropriately.

They loose all rating when not installed as per manufacturer's instructions. This is not how they are designed to be installed. This is just complicating things IMHO.

Tape is my idea and just extra.

Fair enough but trying to fit a gland plate to a membrane is not the way to go IMHO. I think you can forget about rewiring easily with or without a gland plate. They are not designed to ease rewiring in this scenario.


The best chance for rewiring is a continuos conduit, even then it may not be possible.

hesker

2011 wrote: »

They loose all rating when not installed as per manufacturer's instructions. This is not how they are designed to be installed. This is just complicating things .

So are PG glands designed to be installed for this application?

2011

hesker wrote: »

So are PG glands designed to be installed for this application?

In cladding as suggested, absolutely.

hesker

2011 wrote: »

In cladding as suggested, absolutely.

To be clear it's not for install in or on cladding. It's on the external face of the interior structural wall, membrane side, which will be hidden when cladding is fitted.

2011

hesker wrote: »

To be clear it's not for install in or on cladding. It's on the external face of the interior structural wall, membrane side, which will be hidden when cladding is fitted.

Sorry, I don't understand. If it is an internal wall how does it have an exterior face? Your first post states:

This is in relation to an external lighting circuit with external switches.

This sounded like a switch on an external wall to me

Either way if an SWA cable needs to pass through cladding it would be good if it passes through a stuffing gland. Another option might be to use steel conduit instead.

hesker

2011 wrote: »

Sorry, I don't understand. If it is an internal wall how does it have an exterior face? Your first post states:

This sounded like a switch on an external wall to me

Either way if an SWA cable needs to pass through cladding it would be good if it passes through a stuffing gland. Another option might be to use steel conduit instead.

I probably need to draw a diagram as some of my description has been confusing.

Anyway discussion will be redundant if I get this removable cladding timber to work.

2011

hesker wrote: »

I probably need to draw a diagram as some of my description has been confusing.

Anyway discussion will be redundant if I get this removable cladding timber to work.

Fair enough.

I think I may have misunderstood the cladding. I imagined metal cladding on the outside of the shed like that shown in the picture below. This would work well with a stuffing gland, but not suitable for wooden cladding which is what I now think you have.

These things always make more sense when you see them in the flesh

It may be possible to gland directly into the back of the switch, that way no cabling would be visible. If you use an SWA with a few spare cores it may be possible to add / modify at a later date.

On another note an MK Masterseal switch might be a good option to consider. Good IP rating, quality component, 2 gang 2 way available and a little LED light that helps you find it in the dark (requires a neutral to work).

hesker

The attached image (dblstud) is pretty close to my setup.

Differences
- My timber cladding is vertical, but it is nailed on to battens and counterbattens as in the pic
- I have a layer of OSB sheathing between the structural load bearing stud wall and the vapour open weather tight membrane
- I will probably use something like rockwool for insulation rather then dense packed cellulose

So what am I asking an electrician to do:

• Mount a switch on the outside wall of my house and a switch on the outside of the cladding of the shed.
• Two light circuits will be fed off a consumer unit in the shed.
• Lights will most likely be soffit downlighters on shed (front & back).
• Cable between the two switches will be buried underground
• Live feed from inside the shed will have to pass through the internal vapour control layer, wall insulation, OSB sheathing, vapour membrane, across the cavity and through the cladding to the switch (back entry).
• Cable from the shed switch to the house switch will travel back across the cavity through the membrane and OSB and down through the floor (suspended) and underground where it will travel to the switch at the house.
• Neutral will go from lights back to the shed CU.

I've attached a fairly crappy drawing of this.

So it's where the cables penetrate the membrane (black colour in the pic) that I want to fit the glands now before I complete cladding. The cladding is all tongue and groove and once mounted it's all locked in. You can't just leave one bit off. But I nearly have a solution to that. I'll know tomorrow.

hesker

Removable timber worked out fine. Access for electrician will be no problem.