Cable Support

[Marvo]

I have been interested in multiple comments that have cropped up around the forum about the need to support FT+e cabling on vertical drops. Our local regs offer almost no guidance on this issue (just the word 'adequate') and it's not uncommon to see FT+e cables installed in 20 or 25mm PVC conduit that vertically drop (or rise, depending how you look at it) for 2 or 3 stories. I've yet to hear about faults occurring because of this practice but I've seen suggestions here that even the drop from a socket to just under the floor should be supported which I'm guessing would be only around 500mm.

Just wondered what you feel the maximum unsupported drop ought to be and why. I even dug out some of my apprenticeship notes and we were told to limit it to 20 meters by design and 25 meters max if absolutely necessary. These figures I assume came from the structural limitations of the cable as published by the manufacturers.

 

[Adam W]

I seem to remember it's a maximum of 5 metres otherwise you need to support the cables with something such as a 'pin rack'.

 

[imago]

The reasoning I was given for this was that the support should protect the cable from it's own weight causing caffing where it leaves the vertical, and to prevent the chance of loading on any terminations were the unsupported weight of cable to pull on them.

I don't believe that it has anything to do with the tensile strength of the cable itself. If that were the case manufacturers (and regulations) would prohibit 'pulling' cables.

 

[Marvo]

There's possibly a difference in the regs between our countries. The entry and exit of cables for us is covered as a completely separate area and involves guidance about glanding, bushing, cable clamps etc which covers chaffing and strain relief at terminations. The supporting of cabling on vertical runs, especially in conduit or even trunking isn't so well covered.