atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Service Loops

sounds like canadian tire up here, they had the canadian tire 2000 model of stores being built, they ran all checkout cableing in the floor. now they have gotten this idea to move the checkouts to in front of what was the 'in' door and use the out door as an 'in' this means all the cableing now for the checkouts is from the ceiling in jiffy poles. looks like hell.

I do not see all situations that everyone else does, but I have found this works for me in most cases.

Look at the concentration point, and which direction your cables will approach the room from. As an example, for the cables coming from the East, put in a cable path that comes in to the North from East to West past the end point, then turns South, then turns East, and to the end point. Try to keep inside any obstacles that might keep you from re-routing if needed to take a more direct path(organic service loop created). If you use big J hooks stay on the inside of the hook with the cable as much as possible, or use ones which have the swivel. Other cable hangers can always be disconnected to free the cable in the rare case where a service loop event does not require a re-termination of the cable. I would always bid a service loop event as if I was going to re-terminate everything anyway in most cases since patch panels are not designed to go on the road, and remain terminated anyway.

On the station end, leave some if you want, but a cable path designed can tend to leave some possible re-routing slack as my above paragraph may hint towards.

Note, most of what I run is above a drop ceiling at the concentration ends of things at least.

My $0.275 worth (ajusted for inflation) is that we will leave a service loop above a drop ceiling as long as we can suspend it on a J hook or very loosely tie it to a structural member of some sort, but not on the ceiling tile it self. At the wire closet or patch panel, we basically do not leave any in order to keep everything looking neat.

I also would not leave a loop on the ceiling tile, but when you go around the patch panel area before going into it with your cable path it creates an easy, manageable, neat looking service loop that most do not even realize is there. If you end up needing the loop you simply re-route by a direct route not going around the patch panel area first. It works for me, and costs very little to implement other than having to run the cable the additional length to get around the looped cable path.

In the IDF/MDF rooms, I leave enough wire to reach the floor, plus a little extra (usually 10-14'). For feeds I leave close to double that - few things are more aggrivating to me than pulling 100pr cable through 3 floors only to find it's 10' too short and having to reorder and repull it. I pull enough wire to put in service loops, but I rarely find them there after the 66/110 block and patch panels are installed.

Last two jobs where I pulled enough coax for service loops, TWC used the length to go all the way across our backboard. :grr:

For boxes (wood stud buildings), I leave ~30" of wire in/out each on a prewire. Sometimes I've had to move a box over one stud either way, and that usually means rerunning home runs if there's only 12" of wire hanging out. 18" of wire X 500 drops does add up, but is dwarfed by the cost of opening up a finished wall to properly terminate a short wire or a box that has to be moved.

If it's in conduit, I leave enough in the box to trim out three times (~18" cat-whatever, 10" coax)

CCTV and access point drops get plenty of extra wire (~20') if they are in accessable ceilings - too many times I've seen the owner change his mind on cameras ("I want it here, not there...), or access points have a small lapse in coverage that can be rectified by moving them a little bit.

'course, Hilton is going to have their IT guys put a 7' patch cord on their WAPs no matter how much extra wire I leave them. :bang:

I leave plenty for sound drops as well, since lobby and other 1st floor ceiling plans often have a way of getting changed w/o me knowing. It's kinda hard to mount a speaker inside of a light fixture.

I also place a small service loop (a foot or so) out of conduit stubs above drop ceilings, logic being that *if* a splice has to be made, there is wire with which to work, and that if the wire is yanked, the loop will come undone rather than the cable getting stretched or yanked out of the box.

Jeff: one wire cut to 10"? I'd kill to have that drywall crew if that was their only mistake. I've had to buy additional tools to trim coax due to about 3" of good wire sticking out of the box (good ol' Rotozip). I hate Scotchlocks, but I've used more than I care to admit.

Sorry for this ridiculously long post re: service loops - I just really dislike working with short wires and doing things twice. I like to make sure the next man can do his job, especially since I'm often the next man.

I'd more than appreciate any feedback (good or bad) on the above practices.

We usually try to leave a good 10' service loop at the MDF. Unlike what others have said here, we have run into instances where the phone system or data panel has had to be moved many times.

I have had quite a few times where I wish they had left a service loop...so I always try to leave plenty at each end.

The other times it has really saved us is where we find out we put our hardware someplace that was earmarked for another contractors stuff or shelving, etc.

I always leave as much slack as possible in the run, and try to leave adequate loops at both ends. As was said there's no real standard, just recommendations from the various official bodies.
There is one situation though where I ALWAYS arrange for loops: when a CAT5E (or above) data run is less than 45ft/15m. There is convincing evidence that you get far-end xtalk and/or signal bounceback from the terminations being so close. There's no standard for this either. I just like to play it safe on the proper minimum distances.

There is another thing no one has mentioned. Have you noticed when you plan a service loop and you have say 100 cables hanging down out of the ceiling ...... there are ALWAYS 2-3 cables that are too short!!!!