SWA inner cores direct to CU?

[tttonyyy]

Hoping to run this by members to be sure all is OK.

I've got an up to 5kW load in an outbuilding.

I'm in the process of digging in 25m of 2 core SWA of the 6mm variety to a depth of 450mm, tape will be laid over at half-burial depth. Planning on using the armour as CPC, exporting the earth to the outbuilding as well (TN system).

When the cable reaches the house it'll be clipped to the wall 300mm up from ground level for a 5m run, and side-enter an outside IP66 box with appropriate glanding.

Now, what I was thinking, rather than run a short bit of T&E from the CU on the inside to the IP66 box, would it be acceptable to just run the inner part of the SWA through the wall to the CU directly, and bond a separate earth between the CU through the wall to the gland on the SWA?

I could do this both ends and therefore be doubly extra sure that any water ingress in the outside box wouldn't come into contact with live terminal blocks.

Are they any issues with doing this?

Thanks in advance.

 

[ricicle]

P1$$ poor in my opinion and I don't think the bedding layer of SWA counts as sheathing anyway.

 

[holmslaw]

..

 

[tttonyyy]

Its rough, but ok as long as the the inner sheath has complete mechanical protection.

Also, bottom entry is preferred for all external work and if properly installed there should'nt be any water ingress.

OK, no problem - bottom entry it is.

 

[Taylortwocities]

And run the inner sheath through some conduit as it goes through the wall.. It is not very robust as it depends on there being some nice steel armour to protect its delicate hide.

 

[tttonyyy]

OK thanks. TBH if it's that much more delicate than T&E (didn't realise it was) I'll just shove T&E through the wall and be done with it, especially if that's seen as the "proper" way.

Right - glad I asked now.

Any other aspects of the install that I've overlooked?

With the termination box, do you drill the wall and the back of the box, and slap loads of sealant behind it to keep the water out?

 

[Spark123]

I'll second what TTC said, you can run the cores in plastic conduit (or even flexible conduit) for the short length, using the correct adaptors for the conduit to ensure it is watertight on the outside.
I take it you know about Part P, this is notifiable work.

 

[ban-all-sheds]

Let's put it this way - some bedding layers are so soft you can cut through them with a fingernail.

Why have any box on the outside though?

Bring the SWA, complete with armour, through the wall, and if you can't gland it directly into the CU put an adaptable box right next to it, gland the SWA into that and take the inner cores and the flying earth lead through into the CU.

 

[securespark]

Sorry, I can't help myself...

bottom entry is preferred

Oooh, Matron!

 

[tttonyyy]

Wow, 34k posts. I thought I was over-dedicated on the homebrew biodiesel forum, but that puts me to shame!

Let's put it this way - some bedding layers are so soft you can cut through them with a fingernail.

Really? Yeek - definitely won't be trying to route that through a wall then, conduit or no.

Why have any box on the outside though?

Bring the SWA, complete with armour, through the wall, and if you can't gland it directly into the CU put an adaptable box right next to it, gland the SWA into that and take the inner cores and the flying earth lead through into the CU.

Did consider that, but presumably that requires drilling the wall at an angle since the SWA probably has a greater turn radius than my old 4x4.

Plus, I'm very good at punching odd shaped holes out of the back of walls with the SDS drill and a junction box might be a good way to hide that

I'll have a look at the SWA tomorrow and see how tight it looks like it'll turn.

Another thing - supporting when clipped to a wall - I see TLC Direct do cable cleats but it's unclear how these are fastened to a surface? I don't think I can use masonary nails on the clips as the render on our house appears to be laced with diamond (or at least depleted Uranium) for extra toughness. Masonary nails don't touch it.

 

[bernardgreen]

Using the armouring as the CPC needs care that the impedance is low enough to ensure correct operation of the protective devices.

There is also the small but not insignificant risk of the armouring corroding if the outer sheath is damaged and there is ground moisture ingress. If the CPC is from derived from a neutral ( PME system ) then the difference in potential between the armouring ( at the potential of the neutral ) and true ground could accelerate corrosion.

Taking the cores of the SWA into the consumer unit is acceptable provided ( as others have mentioned ) that they are mechanically protected. This method has the advantage of not having to have a junction between SWA and twin and earth.

 

[EFLImpudence]

Another thing - supporting when clipped to a wall - I see TLC Direct do cable cleats but it's unclear how these are fastened to a surface?

They are held with plugs and screws.

 

[EFLImpudence]

Did consider that, but presumably that requires drilling the wall at an angle since the SWA probably has a greater turn radius than my old 4x4.

Find the mortar between courses and drill out a curved route.

 

[ban-all-sheds]

Wow, 34k posts. I thought I was over-dedicated on the homebrew biodiesel forum, but that puts me to shame!

I'll make a mental note of that in case I get a diesel genny.

Did consider that, but presumably that requires drilling the wall at an angle since the SWA probably has a greater turn radius than my old 4x4.

You want it at an angle so that water doesn't run inside, and if it's coming up out of the ground it's heading upwards, which is just what you want.

Plus, I'm very good at punching odd shaped holes out of the back of walls with the SDS drill and a junction box might be a good way to hide that

Yo.

I find that starting with a small bit, and coming off the hammer near the end avoids a large blow, and once started you can go from each end inwards. Do the first one from outside to in - a bit of blown plaster is easier to fix than external brickwork.

 

[tttonyyy]

I find that starting with a small bit, and coming off the hammer near the end avoids a large blow, and once started you can go from each end inwards. Do the first one from outside to in - a bit of blown plaster is easier to fix than external brickwork.

Or, I end up drilling into the back of the CU accidentally, one of the two