Bunched cables though stud timbers

[frank999]

Hi,

I have 6x 1.5 and 1x 2.5 T&E threaded through a hole cut through 3x 2x4 stud wall timbers - all timbers fixed together to form one thick post, the cables form quite a bunch, I understand cables that are in conduit need air free around them to 'breath', 55% free (45% for the cables - this article refers: http://www.tlc-direct.co.uk/Book/4.5.3.htm ) does this rule apply in cables through timbers - as the length is only 150mm or so ?

The stud has 50mm insulation friction fitted, so I have cables also run in the other 50mm void.

The bunch of cables then run inside the stud wall, they are not in the safe zone, run in 25x38mm conduit inside the stud , so are not 50mm from the surface - I assume metal capping one side would suffice to satisfy Regs.(dont need any other side as that is 50mm from surface.

I also have a spliced cable in the stud that will be sealed up behind the plaster board - the splice is contained in a MF BS7533 Wagobox. But with the insulation the Wagobox again is not 50mm from one side of the stud, would a small length of metal capping satisfy Regs.

Thanks

 

[ban-all-sheds]

There are details in the regs of what cable spacing has to be to count as bunched, or grouped - I don't have time right now to look it up. Later, unless someone else does it.

But I can tell you that if concealed cables need mechanical protection because of where they are then metal capping will not do - you'll need to put them in steel conduit.

You're sure they aren't in a "safe zone"? Who did that?

And what do you mean by "splice"?

 

[JohnW2]

There are details in the regs of what cable spacing has to be to count as bunched, or grouped - I don't have time right now to look it up. Later, unless someone else does it.

Unless the hole in the timbers is ridiculously large, I'm sure that what the OP described will qualify as 'grouping' per the regs. One of the problems with the regs in this area is that, unlike the situation with cables passing through insulation, (and unless I'm missing it) the regs do not appear to have anything to say about the situation in which only a very short length of the cables is 'grouped'. I'm sure that such 'short grouping' (e.g. where cables leave a CU - or, indeed, when two or more cables pass through a small hole in timber, as per the OP) is very frequently 'overlooked'.

But I can tell you that if concealed cables need mechanical protection because of where they are then metal capping will not do - you'll need to put them in steel conduit.

True. I imagine that the OP's "25x38mm conduit" is probably some sort of plastic trunking? As for 'capping', I suppose it depends what it is - 3mm steel,or equivalent, would probably be OK, wouldn't it?

Kind Regards, John

 

[frank999]

It would be handy to know what cable spacing has to be, to be classed as bunched, the cables are 6x 1.5 T&E for lighting, and 1x 2.5 T&E which is the supply.

I've uploaded pics, but cant see them in my Albums for some reason.

I've drilled out the hole some more to try attain 55% free air around them.

Regarding 'protection', does this mean physical protection ? - or RCD protection, my understanding is any cables less than 50mm from the surface require RCD protection - which all new consumer units have anyway ...

But I guess both types of protection are best, in practice you don't want any one drilling or screwing through cables - even if they are in a safe zone.

In theory - circuits with RCD protection, less than 50mm from the surface dont need physical protection - its by the hinges of a door in a corner of a bathroom - so unlikely to be subject to any intrusion.

If required though 50mm Galv trunking can be installed - the Wagobox and the bunch of cables will all fit, but it seems like overkill, 2 layers of metal capping (one on top of the other) would be much easier to install - but then again the other side is not covered - and trunking looks the better option ...

Any suggestions appreciated.

Splice: a join in 2.5 T&E cable.

Thanks

Just found this article which is very helpful:
http://www.google.co.uk/url?sa=t&rc...D2WQybnV014kwy94ZWBTAZw&bvm=bv.83339334,d.d24

This article suggests as I, an 'ordinary person' will need to use the trunking ...

 

[Taylortwocities]

picture is not very clear,

Picture?


Did you follow these instructions?

//www.diynot.com/forums/viewtopic.php?t=129539

 

[frank999]

Uploaded images, just cant see album in drop down menu on 'show my images' when posting, all my other albums are there - is there a time lag between uploading and being available ?:

Album is 'Stud Cables' ...

//www.diynot.com/network/frank999/albums/

 

[JohnW2]

Album is 'Stud Cables' ... //www.diynot.com/network/frank999/albums/

Unless I'm missing something, there doesn't appear to be an album by that name there!

Kind Regards, John

 

[frank999]

Umm, try this:

//www.diynot.com/network/frank999/albums/23501

Could it be to privacy settings? was set to public I'm sure, although cant see those now the album is uploaded.

 

[JohnW2]

It would be handy to know what cable spacing has to be, to be classed as bunched, the cables are 6x 1.5 T&E for lighting, and 1x 2.5 T&E which is the supply.

It general, to escape from any degree of de-rating for grouping, cables have to be separated by a clearance of at least 2 cable diameters. That is clearly far from the case when cables are literally 'bunched'- e.g. to go through a hole. However, as I've said, I suspect that may often be 'overlooked' when the grouping affects only a very small length of cables!

Regarding 'protection', does this mean physical protection ? - or RCD protection, my understanding is any cables less than 50mm from the surface require RCD protection - which all new consumer units have anyway ...

The two are effectively alternatives. If the cable is buried <50mm deep then it either has to have adequate mechanical protection (e.g. steel conduit) or RCD protection. Of course, there may be other reasons for needing RCD protection, even if the cable is adequately mechanically protected - e.g. if it supplies any new sockets or is a new supply to a bathroom.

Kind Regards, John

 

[JohnW2]

Umm, try this: //www.diynot.com/network/frank999/albums/23501
Could it be to privacy settings? was set to public I'm sure, although cant see those now the album is uploaded.

Now, using that link, I "do not have permission" to view any of your albums

Kind Regards, John

 

[frank999]

Ahh yes, sorry changed on of the permissions.

Bunched cables - 100mm max length.

Bunched cables

• frank999
• 10 Jan 2015
• 1

Wagobox in front of insulation:

Wagobox in stud

• frank999
• 10 Jan 2015
• 1

Rerouted bunch that need to go in trunking - as I am classed an ordinary person installing ...

Bunched cables and wagobox

• frank999
• 10 Jan 2015
• 1

Does the electrical trade use the term 'competent' person, and would he need to be under the supervision of a Trained person ?

 

[RF Lighting]

Those cables are not routed within prescribed safe zones so will need re routing or installing inside steel conduit.

 

[ban-all-sheds]

As for 'capping', I suppose it depends what it is - 3mm steel,or equivalent, would probably be OK, wouldn't it?

Can you buy anything sold as "capping" which is 3mm thick?

And how would you earth it?

If the cable is buried <50mm deep then it either has to have adequate mechanical protection (e.g. steel conduit) or RCD protection.

Don't forget that the latter is not an alternative to the former for cables outside the prescribed safe zones.

 

[ban-all-sheds]

Splice: a join in 2.5 T&E cable.

Indeed.

What sort of joint?

Bunched cables and wagobox

• frank999
• 10 Jan 2015
• 1

Who did that?

 

[JohnW2]

As for 'capping', I suppose it depends what it is - 3mm steel,or equivalent, would probably be OK, wouldn't it?

Can you buy anything sold as "capping" which is 3mm thick? ... And how would you earth it?

I don't know whether one could buy it with such a name. As for earthing it, I'm sure one could find a way, but some might argue that (surprisingly) 522.6.101(iv) doesn't explicitly say that 'mechanical protection' (as opposed to sheathing, conduit, trunking or ducting) necessarily has to be earthed (although it is clearly desirable that, if conductive, it should be).

If the cable is buried <50mm deep then it either has to have adequate mechanical protection (e.g. steel conduit) or RCD protection.

Don't forget that the latter is not an alternative to the former for cables outside the prescribed safe zones.

True - I should also have said that.

Kind Regards, John