Clamping telephone cable in vertical trunking

[jim_in_sussex]

(Running telephone cable from attic to ground floor.)

Many thanks for prev help with the correct cable to use.

After due deliberation I am going to run 2 x 3-pair telephone cables +

1 x CAT5 cable the whole way.

I am doing it this way as it leaves plenty of surplus capacity (& the phone wire for which there is no other use came in a 100m reel) + the difficult bit -feeding the cable - is done once & for all.

The main run down will be a vertical drop from the attic into the cellar - around 9 meters through mini-trunking (not bought yet, but

16x25mm unless there are other suggestions).

I presume the cable will need securing in the trunking? - What is the best fixing method & how far apart should the fixings be?

TIA

[Nigel Molesworth]

Strange as it may seem, no.

[Owain]

25x25mm. Trunking can never be too big.

Phone and Cat5 cables should be okay for that length. The main problems are the cable's own weight, and stress at the top of the cables where they pass into the vertical trunking. Heavy mains cables in long vertical ducts also have to take into account self-geenerated heat rising up the duct.

The simplest way of 'fixing' them is just to use some pegs a few inches above each other in a vertical line and 'slalom' the cables between the pegs ie

| | \ \ 0|

[gtl]

If you really must then buy some sticky pads and use cable ties. spacing depends on what you think looks nice as no one will see it once the lid is on the trunking. I would be looking at dropping the cables down a cavity wall instead as trunking looks ugly.

[Andy Wade]

The On-Site Guide (Appendix 4) recommends supports at no more then 5m intervals on vertical drops in trunking, so in this case one intermediate support is advisable. Don't use sticky pads, which always tend to fail by sliding when loaded in shear. I'd put a few turns of PVC tape round the two cables and then attach to a support peg (such as a screw thro' the back or side of the trunking) using a cable tie.

[Dave Liquorice]

Curious that sticky pads are frowned upon for failing in shear but PVC tape that also fails in shear is OK. B-)

Think I'd make something purely out of cable ties, one around the cables and another to attach that to a peg or perhaps a tie, maybe the same one, threaded through two holes in the duct. What ever this point would have easy access for when more cables need to added/changed or WHY.

[Andy Wade]

Experience suggests... Anyway the tape would be loaded in compression by the pinching effect of the cable tie(s), which will tend to stop it sliding around.

Yes, good advice, although this is all gilding the lilly a bit for a couple of lightweight telephone cables.

[Dave Liquorice]

Ah, I didn't think you where putting a tie around the cables as well, in which case wy bother with the tape which will just make the cables messy with the ozzed goo after a while.

Agree, something to spread/ease the load at the top but otherwise I'd just let 'em dangle. Easy access points are not really gilding though, you'll be cursing not putting them in later on.