Trunking cables from CU

[Alan53]

My CU is mounted in the garage and I feel that I should protect the cables running in to it. There is a 70cm run of cable before the cables go throuth the wall in to the loft.
My dilema is that as there are 11 cables I believe that I shoud de rate the cables if I put them in a single run of trunking and this would then mean having to increase cable sizes for nearly everything, not very practical.

My thinking from the practical side is that if I leave the cables well spread out and clipped against the wall, or something else, as the run is also short there should be minimal thermal issues, I suspect there are some formula's somwhere that I can use to jusify this approach.


If I take the above approach the easiest solution would be to build some boxing over the existing installation, can someone advise on what materials have suitable fire rating?

Thanks

 

[PrenticeBoyofDerry]

There are tables for calculating trunking capacities these can be found in the on-site guide, there is a link here http://www.tlc-direct.co.uk/Book/4.5.3.htm that will help, it is of an older edition (16th rather than 17th) but I don't think the calculation have changed.
Hope this helps you with your problem.
If the cables are not in danger of any mechanical damage, I would not really be concerned. The one thing that could be an issue is that you say the cables run vertically upwards from your consumer unit, if the cable entry holes are on top of the consumer unit they should comply to IP4X (Protected against solid objects greater than 1.0m)

 

[ban-all-sheds]

My CU is mounted in the garage and I feel that I should protect the cables running in to it.

Why?

 

[Taylortwocities]

If I take the above approach the easiest solution would be to build some boxing over the existing installation, can someone advise on what materials have suitable fire rating?

Thanks

If you must, then boxing the cables would be the easiest, but as BAS saya "why?"

They aren't going to suddenly leap off the wall and strangle somebody. Protection is only necessary if there's danger of damage to the cables (sharp implements, ski poles, grizzly bears in close proximity, etc).

And dont worry about fire resistance of the boxing in materials.
The cables aren't likely to suddenly catch fire. Just think about where the wires go once they disappear into the loft, they will be along side and through wooden joists, etc until they reach their final destinations.

Use plasterboard if you are really nervous. I'd be more worried about the gas and water pipes - very dangerous stuff!

 

[Alan53]

My CU is mounted in the garage and I feel that I should protect the cables running in to it.

Why?

Thanks All for the replies so far,

The reason I am considering protection of the cables is because I use the loft area above the garage for storage of pipe, bit's of wood etc and therefore there is some risk of damage to the cables.

As suggested I will probably use some bit's of wood to box the cables in.

Thanks for the tip on ingress of small objects, other than ensuring that the knockouts were reasonably close to the cables I had not considered this issue, I will find a way to clamp a thin piece of pliable material accross the cables.

There are tables for calculating trunking capacities these can be found in the on-site guide, there is a link here http://www.tlc-direct.co.uk/Book/4.5.3.htm that will help, it is of an older edition (16th rather than 17th) but I don't think the calculation have changed

.


I am still concerned about potential temperature issues and requirements to de-rate cables, my understanding is that the guidlines pointed to by Prentice Boy above describe the physical cable carrying capacity of trunking, they do not deal with any thermal issues caused by large numbers of conductors in a confined space and the derating that may be required. Currently my plan is to work on the basis the cables are clamped to a concreate block wall to give some thermal mass without any direct sunlight on them or the wall, leave plenty of extra space in the boxing and as the run is only 70 cm I should be ok?

Any comments?

Thanks

Alan

 

[PrenticeBoyofDerry]

Thanks for the tip on ingress of small objects, other than ensuring that the knockouts were reasonably close to the cables I had not considered this issue, I will find a way to clamp a thin piece of pliable material accross the cables.

A silicon sealant might be a better option.

I am still concerned about potential temperature issues and requirements to de-rate cables, my understanding is that the guidlines pointed to by Prentice Boy above describe the physical cable carrying capacity of trunking, they do not deal with any thermal issues caused by large numbers of conductors in a confined space and the derating that may be required. Currently my plan is to work on the basis the cables are clamped to a concreate block wall to give some thermal mass without any direct sunlight on them or the wall, leave plenty of extra space in the boxing and as the run is only 70 cm I should be ok?

Any comments?

This to can be calculated using a grouping factor in table 4C1, we need to know the number of circuits.
But your best option may be to put up a simply barrier to prevent damage, that offers plenty of ventilation to the cables.

 

[seasickstevie]

Vertical batten each side, then ...
http://www.tlc-direct.co.uk/Main_Index/Cable_Tray/index.html across.