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Posted By Topic: cable tray

Dannyboy
Apr 21 2018 08:49

Hi All
I have been searching the good book looking for the exact spacing for seperation of services between power cables and data cables in cable tray another industrial sparky said it is 50mm but I just can't put my finger on the reg. Can anyone help


   

Sarmajor
Apr 21 2018 11:15

You can’t finf things in the ESRs that aren’t there.

AS/NZS3008 has lots of useful information about cable installation condition and debating factors relating toinstallation conditions.
   

Sarmajor
Apr 21 2018 11:19

See also AS/NZS3000:2007 3.9.8.4.
   

AlecK
Apr 21 2018 12:49

Unless the data cables are shielded, you'll want way more than 50 m between parallel runs of data & unshielded power cabling.
"3000" clause 3.9.8.4 (c) applies, and points to the TCF Premises Wiring Code of Practice. Fig 3.8 calls for minimum 50 mm - but that's just to deal with safety issues and is nowhere near enough to eliminate interference & data corruption. Basically the more the better. Minimum from unshielded power cable used to be 300 mm [AS/NZS 3080:1996], and it won't be any less now with higher data rates.
   

Blackops
Apr 21 2018 19:51

We do a lot of this - we always use 300mm.

Any data and cable on the same tray is always separated with a divider otherwise.
   

dbuckley
Apr 22 2018 13:56

Alec:

> Unless the data cables are shielded, you'll want way more than 50 m between
> parallel runs of data & unshielded power cabling.

That is some fecking wide tray you've got there boy!

With modern data running in unshelided Cat5 or above, although it not legal you can run the two side by side for the full legal run of a length of Cat5 and have no problems at all. It's not the shielding that does it, its that the signals are balanced, and thus the data signals have common-mode interference rejection.

There used to be a flexible cable for ENG applications, that had mains and signal (including unbalanced video) in a single jacket. It showed what careful design can do to make these two supposedly-incompatible things live in one cable.

Image of specification here: https://i.imgur.com/VDCmRqa.jpg

No longer available, as times have changed and it is no longer necessary.

But what does exist is cable for powered speakers, with mains and audio in one jacket, and cable for intelligent lights, with power and DMX in the one jacket. Most popular is the Sommer "Monolith" cables see http://shop.sommercable.com/en/Cables/Bulk-Cables-Audio/


   

AlecK
Apr 22 2018 17:26

Not extra-wide tray, just the separation as required by the rules - which might well lead to the data not being on the tray at all.

Like "3000", I leave the data transmission specialists to set the rules covering signal rejection, NEXT, attenuation, and all the other things that can go wrong with a data circuit. I know that one over-tight cable tie can be enough to cause a whole bundle of data cables to test as "bad"
   

Sarmajor
Apr 22 2018 17:29

AlecK,
Buckley was referring to the 50m separation instead of 50mm on the tray.
   

Dannyboy
Apr 22 2018 20:12

Thank you all for your input. I will purchase the separation barrier and the problem will go away or lay a conduit as I do not have the 300mm to give in separation space on the tray. Mostly it is just phone cables and or a data link between computers I am running in the tray.
I have used cat 6 which is 230volt rated in the past and run power and pone in the same conduit mostly to kitchen benches. I believe I am ok to do this?
   

AlecK
Apr 23 2018 08:32

This isn't just about the voltage rating [ 3.9.8.3], it's also about EMI. So no, it's NOT OK to put both services in same conduit.
3.9.8.4 says we must follow Fig 3.8 and the TCF Code of Practice; and the Fig sets a minimum of 50 mm separation.