structured cabling...serpentine design?

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cyr0n_k0r

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I'm running through some design documents for an upcoming structured cabling project and it reads as follows.

c) The contractor shall provide a minimum of 10 feet of cable slack at each MDF/IDF, and a minimum of 3 feet of cable slack for each workstation outlet.
i. Do not form a loop with the cable slack at either end of the run. A serpentine design should be used if possible.
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Does anyone know what a serpentine design is? I've tried searching on google but can't find a picture or any documents describing exactly how you go about using this serpentine method.
 
does anyone have pictures of this method?
When did this become popular? I ran cable projects about 4 years ago and contractors were still using loops for the service loop in the rooms above the grid.

Also, why are loops not preferred? Do they introduce any interference?
 
A loop will create a magnetic field equivalent to the data flow of the cable, making it possible for the data to be wirelessly picked up and sniffed. Ok, just kidding, though, that kinda makes sense now that I think about it... Hmmm.... Though I'm thinking they just don't want a loop as if it's inside a wall it will be hard to unloop it. Like say the jack plate is removed and more slack is needed.

I usually do "serpentine design" when I leave slack, though it's the first time I hear that term, I will have to remember that.
 
Looping ethernet cable is contrary to best practice, along with running it parallel to nearby AC elctrical and near fluorescent fixtures, etc. Red was correct in that it can induce current in the coiled loop, but the effect is typically to change the impedance of the cable, which changes the data transmission characteristics.
 
Yes, i think Looping Ethernet Wire can be contrary to best process, along with working that parallel for you to regional AC electrical as well as close to fluorescent fittings, and many others. Checkout Telesystemscorp for more structured cabling services.
 
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Xipher said:
I think that would be almost like a figure 8.
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This. Or another way we did it is to not allow the service loop to touch the run.....so basically no cable can touch the cable....if that makes sense.


We had to do this at Comcast and we would fail inspection if supervisor went behind us.


God, RF theory makes some paranoid people though ;)
 
Yeah, tight coils is against practice, but large open loops will minimally affect cable characteristics. For a serpentine design on the IDF side I would just put some spools horizontally along a wall, with upper and lower spools a foot or two apart, then run the cables around them in an 'S' shape. The same could be done vertically.
If ladder rack was used horizontally, you could pull bundles down, creating 'S' shaped slack.
In a wall, I've got nothing except a figure-8 coil. If you could move the slack back to an overhead horizontal run, do the same thing as in the IDF- hanging slack between Ladder openings/D-rings/Bridle Rings. Dunno if you would want to bundle the slack for neatness, or leave it un-bundled (the slack area only) for easy pulling when repair is needed.
 
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