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Installing DMX cable underground


Arenasou

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Hi All,

 

I'm currently quoting for an installation that has outdoor lighting and I'm unsure about the required spec for the DMX cabling. Power is fine, just standard SWA.

 

Has anyone installed DMX outside before? I have about 20 units that all need a feed, linked in and out.

 

Should I install some conduit / PVC pipe to run the cables in, or can I run DMX over 1.5mm SWA?

 

Any thoughts much appreciated!

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I've got a friend who worked on an outdoor site specific show a few years ago in Scotland. Mid-show they lost control of a whole pile of fixture and when they investigated they found that rabbits had chewed through the DMX lines in several places.
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I suspect you will want to go down the conduit route with standard cable, but for moderate quantities (I think about 100m drum up) specialist cable suppliers like Highblade can over-sheath more or less anything with special over-sheaths, which can be had in UV resistant, rodent repellent and various other grades. We've had some on an offshore wind farm, and it's lasted a couple of years cable tied to the outside of the structure so far!
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I suspect you will want to go down the conduit route with standard cable, but for moderate quantities (I think about 100m drum up) specialist cable suppliers like Highblade can over-sheath more or less anything with special over-sheaths, which can be had in UV resistant, rodent repellent and various other grades. We've had some on an offshore wind farm, and it's lasted a couple of years cable tied to the outside of the structure so far!

 

Do you have much of a rodent problem on an offshore wind farm?! :P

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Rats eat them.

 

 

20 years ago I saw heavy duty SWA fibre cable which had been eaten through by rats. It was only laid for a couple of weeks and cost over 20K to replace. The contractors managed to seal the ducts with the rats already in them...

 

 

 

 

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One of th eguys at our theatre installs alarms as his day job, and he is forever having to replace the ducting and cabling from outdoor sensors and cameras where rats have found a way in. Doesn't seem to matter what you do, they will get to the cables and they will chew through them, unless they are seriously (and expensively) armoured..
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I'm afraid I'm offering yet another rat warning. They really do chew their way through data cables. We've run data with SWA in suitable large diameter underground piping, but seal the ends and even chuck some rat bait in there too in case there are already occupants.

 

You won't appreciate the rat problem until you are troubleshooting a link and pull a defective cable out to reveal either a complete break in the cable or a very messy chewed section.

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my friend in the pest control world tells me that rats have a particular fondness for fibre cables - apparently rat’s teeth (like all rodents) keep growing and need to be regularly ground down. In the urban world, they don’t have enough things to chew, and the kevlar reinforcement in fibre cables is quite attractive to them....
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