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

I know a lot of us leave service loops, but how many have actually had to use them? Sometimes they seem a bit trivial to me. Especially when they are seen, and you have to try and make them nice and neat. The first time you have to use one, the neatness factor pretty much goes away, doesn't it? Doesn't the cost of leaving that much cable and spending the time dressing it outweigh the cost of re-running one or two cables? I know this is a stupid question; I've just always wondered.

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| Signal Communication Systems - Fresno, CA |

| Telephone Systems, Voicemail Syste... & Data Cabling - Central Valley, CA

service loops are only really helpful when a rack has to be moved or equipment is relocated to different place on the wall which happens as customers grow or change. I usually try to hide them above the ceiling or in the rack. I believe service loops are required, maybe not by code but a few certification seminars I've been to had specs for almost rediculous service loop lengths. When your pulling 500 cables you would need another room for the service loops

I always try to leave a service loop on both ends! When ever I pull cable to a office I try to leave enough to reach any side of the wall. Saved me more than one occasion.

I've used up service loops in the past. Mainly when (as Bikechuck said) I have had to relocate a rack in the room or the room was remodeled and the Patch Panels and switches had to be temporarily "hung" in a safer place.

Yes, they are a pain in the A%# to work up and make neat looking and I think they only provide designers and architects an easy excuse to be lazy sometimes in their designs. But when you need one, pop open the tiles and find one, the sigh of relief is audible from miles away.

I personnaly always thought that service loops where a sign of "ah, I don't feel like pulling all that cable down the wall" I typically only leave one if it is an exceptionally long pull, or hard to fish wall. I have only used one a couple of times.

I do not believe the Telecommunications Industry Assn standards address service loops for cabling. BICSI just recommends putting cabling in a figure eight instead of a bid loop. Big loops can degrade category cabling's performance. If a client plans on having a lot of MAC work I would recommend using a Consolidation Point (CP) or a MUTOA (Multi-User Telecommunications Outlet Assembly) in the work area. Also any service loops need to be added in the total length allowed for the cabling (e.g. 295' for a permanent link). MUTOAs also need to be used based upon a formula because of the use of long patch cords.

I always leave service loops when they can be hidden, and overall length of the run allows for it. I've used service loops many times and been very thankful to have them. For me it's usually a matter of having to move racks and/or patch panels, in which case you wouldn't be able to just run one or two cables. It is challenging to keep things neat when you have to use a service loop, but it's not impossible.

Just don't go overboard when you make your service loops. One or two loops at the work area side should be plenty. If you have a large bundle of cables, you should be able to incorporate some slack without actually making big loops. A service loop doesn't have to be a coil of cable.

How come? Crosstalk?

I think it's a good diea to leave a few extra feet (8 or 10) in the ceiling at the office or workstation end of the pull. But to try to do so above the telcom closet is a real pain in the butt.

I agree with you, Mike. to the Board!

Is it the actual loop, literally being in a circle, that is the problem. Is this why Mr Cooper recommended a figure 8?
Or, is the problem that as one loops the cable it is running parallel to itself?

Numerous factors can attribute to large service loops being associated with crosstalk and RF interference (primarily the environment in which the loops are located, quantity and distance between any turns, physical location/direction that they are facing, UTP considerations, etc.)

5Yrs, I've only had to utilize service loops on one occasion: Several CSUs were removed from a rack, and we relocated the patch panels that were originally located above the CSUs so that their front port DS1 wiring would better align with patch panels in adjacent racks. Without the excess cable to work with, any other alternative would have included pulling and terminating new 100 pair cables.

As stated earlier in this thread, service loops don't need to be coils. What we have started to do on the equipment room side is route the cable in a manner so that it has about 5-6' of "slack". We route it past were it needs to go then come back. kind of creating an "S" curve. This creates enough slack so that the rack can be moved if need be.

We were subcontracted to do a job in which we had to remove 6 open racks housing data equipment and replace with locking cabinets. It would have been impossible if there had not been existing services loops.

WOW three years and still a valid topic. :rofl:

I like 3 feet at the station end and 6 at the rack. The reasons? well first the only reason for slack at the station end would be retermination because of a failure. If relocation is needed then I would rather run new. As for the rack end the length is determined by the ability to move a rack in a given MDF or IDF. Most "rack rooms" dont allow for too much movement. So big room plenty of slack small room little slack. You get the point.

**Just my two bits**

I always like to leave service loops for the obvious reasons stated in the above posts.

Wish Silversam and other 'Bell-trained' guys would chime in here. Until I went to work for my present employer, 'service loops' were considered sloppy work. There is always a couple of feet of 'slack' for reterminations. If you need any more, you really need to repull the run! Move a rack, BS! "Poor planning on your part, does NOT constitute an emergency on my part". Hard to get along with, maybe. But prior planning results in fewer problems! John C. (Not Garand)

Bell trained guy here, we never left service loops, just a foot or so slack incase of jack re-terminations. Never had to move the blocks. I do now leave slack at the station end for one reason only, sheet rockers. Terminal end if it's a suspended ceiling or somewhere I can conceal it yes. For patch panels, yes.

I learned the drywall guy part the hard way. On the job I did this summer, one of my cables got cut and I had less than a foot to work with coming out of the box. I was able to make it all work
I did leave at least 10 feet of slack at the patch panel end, because the customer had custom cabinets made to go around the wall mounted panel (long story).

I'm not a "Bell Trained Guy", though I worked with quite a few and had a number of years with GTE (We NEVER considered ourselves Bell! Heaven forbid. ANYTHING, but. We, were better then Bell [or at least, so we thought]).

In any event, we never left service loops.

A foot or two of slack in the ceiling for repair of a connector/amphenol, etc. Otherwise, No.

In a switchroom, (CO or PBX) if you left a 6-10 foot loop on every cable you would never have room for anything and the sheer mass of cables would keep you from getting to the slack. (Switchrooms [at least in my day] had a LOT of cable.

I would have to agree with John C. - If I have to move a rack, I'll recable it. Why would I have to move it, anyway? How often does something like that (whatever that is) come up?

When I wired computer rooms, the CGs always wanted 30' of slack under each cabinet in the raised floor)"in case they wanted to move anything themselves". Every 5 years or so, they paid us to strip out the computer rooms completely because there was so much cable under the floor the tiles wouldn't sit flush. We always made a fortune on them.

I never remember them moving anything themselves. Ever. When the rare occasion came and they called us to move something, if it reached, we would stretch it out, but usually we stripped it all out and rewired it.

Sorry for being so contrary, but that's how I feel. Finger loops on x-connects and on cable, a drip loop at the station end and s little less then that at the cabinet/rack.


Sam

I also trained in a NOTC/GTE central office. We had enough cable issuses to worry about than service loops. You mined as much cable as you could and sewed in the new runs on top of the old, never leaving "service loops." If a bay needed to be relocated, you ran new cable to it.

Cross-cuts were different, beccaue you needed some slack to do transfer and regrouping and to pull a jumper to ID it.

The last two retail jobs I did had the "service loops". I had to laugh. The longest run engineered for 294' ended up at 309'. It just barely passed the scanner test.

Carl

I only ever left some slack on the jack side if something needed to be reterminated. On the patch panel side? Never, too many cables and once it's installed if it has to move it will typically be more than a 1.5' slack loop would allow.

You can do service loops and keep them neat and it doesn't have to take any extra time or effort. What I do is to install my pipes and insulator rings then all the cable drops go down through them plus 12 feet more than is needed. 10 for the loop, 2 for working room. They are all appropriately tagged with numeric strips. That would be the concentration point. At the wall side, you simply pull out about 10 feet more than you need then make a nice neat loop in the ceiling. You typically will have 4 cables, sometimes 6 so it's easy. A couple of zip ties and you're good to go. Now back to the concentration point. Once you have all your cables run you climb up into the ceiling space and pull back the excess making a nice large loop. I can typically loop 18 or so cables at a time without them becoming too unweildy. Then I secure them onto j-hooks I have installed just for this purpose. I get excellent strain relief, no pinched cables and plenty of support. Now if the ceiling space is very low then an 8-shape lying on its side is the best solution. I like to use a large bridle rings for this.

Either way it really takes no extra time at all. It burns through a lot more cable but the specs call for it and I feel it is a mark of a quality install. Few people can know the difference but the few who can, can make your life miserable.

i am an old general telephone guy. we never used service loops but i do now for the reasons mentioned above.

We have gotten in the practice of using a sections of cable tray say 5' in length above the rack, making basically an S shape with the cable. Gives it a clean look like you spent alot of time on it (not) and you can then strap your cable bundle to the cable tray to keep it neat. As far as needing loops, I have yet to need one at a rack but yes at the jacks, only takes one time swearing cause you only have a few inches to get reterminated to want that extra couple of feet.

It's been my experience that those who don't test their work, don't leave service loops. This is just a rant... it's inevitable that I have to end up running a new cable because so many fly-by-nights pull taught and staple everything like it's going out of style.

This was a good question. I, personally, leave a service loop all the time... it's going to do more good than bad. Really, they don't do much bad at all. I leave about 8' and tuck.

Could it be that service loops began as a "How can we sell %10 percent more product"?

This is a question I feel compelled to ask the forum.

That's what they want you to think, but it's really for national security. All those extra loops are there so the gov't can install microphones and spy cameras once Bush is re-elected.

It's become the norm for many of the reasons stated. However I for one haven't had to move a patch panel, or blocks. I really doubt anyone does it because they can get a few more bucks off the cable. Could be wrong though.

We only leave service loops on our OSP cables. I will leave a little copper in the handholds but mainly fiber.

If it's inside we may leave a foot to 18" in the wall at the outlets, but thats it. None in the closets.

Although the exact amount of required cable slack depends on the size and layout of the
connecting hardware at the TR or TE and the work area, the recommended minimum
amount of cable slack:
• At the TR or TE is 3 m (10 ft).
• In the suspended ceiling for the telecommunications outlet is 1 m (3.28 ft).
NOTE: If a horizontal distribution method other than ceiling distribution is used, the length of
recommended minimum amount of cable slack should be adjusted accordingly

Reprinted from TDMM 11th Edition
Page 4-71

Jeff

I have recently done some new cat5 runs for the three walgreens stores in town here. I wish the original installers had left something of a service loop. They all have 5 1/2' rolling cabinets within the pharmacies, no problem getting the wire down the wall with the existing pipe and a 12x12 j box but getting the rolling cabinet more than a foot from the wall was tough. Just enough room for me to squeeze between the shelf and the cabinet. But then these jobs are spec'd from the company when the building goes up. Funny thing, two of the buildings were finished in the last 6 months,thats some foresight.

Yes, service loop in a new hospital here, they needed to move their equipment to another room, and we were able to move some of them from the original rooms which were quite a distance. I leave a service loop just for that reason.,

:thumb:

Bump

I can't see any reason to not leave a service loop. 10' at the station and at least 5' at the rack. I have done a few jobs where the customer did not want them cause it for some reason did not look good from the floor in Walmart.

Redryder-we do a lot of Wal-Mart construction and have never been criticized for a service loop; we do it neatly and coil it above the bottom chord of the joist. Also, at least for camera work in Wal-Mart, the scope requires a 25'service loop.

I worked on the new Super Center in Ocala, Fl and the PM that was running the job flipped out when I had neat service loops on everything I dropped. I worked for Staley at the time.

Every Wal Mart I have been in, you look up and it's a total disaster above every checkout...

Yes , the cabling in Walmart is horrendous. Every 5 to 10 years they do a remodel where they retile all the floors and move everything in the store. That is where the cabling get looking like a rats nest cause the guys are just using what cable is there to make it happen and back up before the sun comes up.

Jeff, that's what we vowed to avoid when we started doing these jobs. I'll try to post some pics from the job we're on now.
Bill

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!!!!

Heck, Noisy, that's easy. Those are the ones that are going to fail, and they're trying to tell you to replace them now! Everybody knows that! Kinda like "Green Side Up" when you're putting down turf, or "The nails that come out of the nail pouch pointed the wrong way are for the other side of whatever you are nailing together"! John C.

The service loop is where some really stupid mistakes happen. Comical stuff. Last summer we were doing a cabling job with about 150 drops and each cable was labeled at the service loop with a number (at the very end of the cable). We left for a 30 minute lunch. Another tech showed up from my company and cut off all the numbers.

Worse - pulled a 12-strand MM fiber that was preterminated on both ends. Before I could say 'stop' the tech working with me cut off the ends, all beautifully terminated. I hung those off my rear view mirror in my van for a long time.

Yet another time, a contractor came in and cut off all my cabling above the ceiling tile because it looked messy and they wanted to impress the new owners.

How did you fix that problem?

Jack

We charged the customer for all new cable and labor and left it up to them to get reimbursed by the other contractor. They paid, don't know if they were ever reimbursed. Documented everything.

Documented everything

I have gotten more and more in the habit of taking digital pictures of our finished work just for the above reasons - service loop or no service loop

Yes, you have to do it. Then when someone destroys your work there is proof that it was done correctly. Our contracts also say that the customer is responsible for replacement of properly installed cabling that is intentionally or negligently cut/removed by someone else. Not sure it would ever hold up, but worth a try.

The real danger is when another contractor is to demo out the old cable and our work gets started before they complete their cutting and yanking.

I try when possible to use a different color cable than is currently in the building if demo is going to be happening after new cable runs begin. If not feesible I make sure what brand cable is being used, and get a different one for the new, so the demo crew can sign off on being informed which color, and or brand the new cable is before they come on site. I ask the demo scope include not removing any of the brand, or color cable I am installing. If I am doing the demo, I use the same method.

where i work the HVAC crew once cut a hole in a concrete floor severing 40 cables and landing the chunk of concrete on the riser. they paid

Noisycow, that's great that you got the owner to do it properly, and that he paid for it. Thumbs up on the documentation and contractual obligations.

zapatogrande - I've recently started taking pictures of work we do for the same reasons.

aarenot - good idea of using different colors than the existing wire.

Jack

I still think my best idea is to have all incoming cables go through a cable path that circles the MDF to the other side thus creating a cable path service loop which can be reterminated skipping the loop around if extra cable is required. This horizontal service loop eliminates the need to create the vertical service loop which is always ugly even at its best practice to implement. Only a trained eye is going to even notice there is a service loop because it is horizontal.

aarenot, I think I see what you are saying now - instead of laying out the wires to take the straighest shot to patch panels/66 blocks (I'm learning guys;)) in the IDF/MDF rooms, you'd route them around the room a bit, like a big U-bend, to take a longer path. Doing this above a drop ceiling wouldn't be visible at all. Am I close?

Jack

Exactly, 4 entry paths (N,S,E,W) to the MDF/IDF, cables from the north loop around to the south entry path, S to the N, E to the W, W to the E before using one of the 4 entry paths. You may not need as many as 4 paths, but you get the idea. The length to get around to the opposite side of the MDF to the far entry path is designed & laid out to be the length of the required HSL Horizontal Service Loop. If you end up needing the length you can simply re-terminate the cable after pulling it back, and re-routing it via the closest entry path rather than the one around the other side of the MDF/IDF. This is all above the drop ceiling, and can be laid out ahead of pulling any cable to ensure you can pull the cable simply as far as you need to, and no farther since your service loop is pulled in already when you get to the MDF, add enough to reach the floor after you get to the rack, and cut it off. No more trying to organize, comb, seperate, make look good a bunch of loops you make by hand & try to hang vertically without making an eyesore. I started doing this years ago, and have never had an issue, in fact not creating coils of cable is probably better when it comes to a performance standpoint of the cable itself. I will never put another vertical service loop without charging extra for it becuase it takes more time to do than a HSL.

When cabling, I leave acsingle small loop at the jack end ( tie wrapped up in the ceiling) and at the closet end I wont leave a loop, but I will hang a J hook or two so that the cable goes the long way down to the rack. This way if you take the cables off the J hooks, you will have an extra 3-5 ft. That in my opinion is enough - not too much.

BTW:You are responding to a post almost 2 years old...

I am with clgjr,

No one in my company asked me when I was apprenticing I just thought, it made sence and told my supervisor about it and he agreed. Having a cable long enough to exit any port at any part of the walls in the office made since. Leave a 2 foot loop in the wall, and the rest curled up above the ceiling.

I don't leave service loops. What i do is bring the cable to the consolidation point in a round about way. Run the cable strait down and over and then back up and terminate all the cable lenghts are equal, this gives you a few extra feet. I did some work for a university they called service loops shoody and did not won't any on ther Campus. Because their SHODDY and end up making a big mesh.

Okay this thread was started in 05 and we have the same topic a few rows down so lets close this one.