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Wiring Issues 1 - Patch Panel
Topic(s):
Submitted by: Sphynx – Tue, 04/14/2009 – 08:52

Many years ago the shop I was working in moved to a newly renovated building. It was decided to clean up the cabling mess created by the three-dozen 3274 control units used in the building. After having been in one location for a long time many of the coax cables had been re-routed and new cables were also brought in. By the time of the move the cables were a mess. The solution was that in the new location we would set up a patch panel. The cables between the control units and the panel would never move. On the back side of the panel coax would come in from all over the building.

It was a great idea but the implementation left a lot to be desired. The electrician tried to make things very neat. Wires leading to either side of the panel were tightly bound with cable ties every six inches. The cables were trimmed to eliminate slack. Finally, the cables were trimmed with a trimmer that was set just a little off so the central wire was too short and just made a connection.

The results were that cables could not be easily moved on the back side (wrong length and tied down) but the hidden problem was that central wire. Anytime someone stepped on one of these neat bundles along the floor or behind the panels, that central wire would pull back the thousandth of an inch and break the connection.

Still, it was all neat and clean looking.

Comment:  Form vs Function

Rated: 3

I guess I would ask, why are people stepping on the wires?

Can you not put a bridge over them, like the ones the fire department uses when a hose is ran over the roadway?

Genxcat – Wed, 04/15/2009 – 07:59

Comment:  Stepping Lively

Rated: -1

The thick bundle of wires (strapped together every six inches) made a small loop on the floor in front of the panel before going into the wiring trough. This was the electricians idea of how to provide the slack for the patch panel. Of course, in order to loose an individual coax, a dozen or so cable ties would have to be cut and all the coax cables would be loose.
As for the bridge, it would not really fit in the space provided, costs money, and you didn't have to stop on the wires if you tried not to.

Sphynx – Thu, 04/16/2009 – 07:55

Comment:  Wiring Issues

Rated: 3

One of the tell tale signs of a good electrical installation is the neatness given to the manner in which the wire and cable is run and supported. The same also applies to the appearance of a distribution panel (aka 'fuse box'); and the care shown in making up splices inside junction boxes.

I used to absolutely hate those who would do a sloppy job. Every time I would have had to install either a switch or receptacle where the wires leading to a splice were so short one could barely connect the device, I would curse the $#!thead that did that job. The same would apply when I had to open up a 'fuse box' and fix some dodo's screw up; and the inside looked like 'Marconi's Nightmare'.

It never hurts to leave a bit of slack; just in case. I once had this boss who complained about leaving "too much slack". One day, I went to finish a house that had been vandalized. All of the wires going into the 'fuse box' were cut; and the boss was there p---ing and moaning about how much that was going to cost him. Since I had wired that house, all I had to do was grab the ends of the cable; and give each one a good tug. Voila, the extra 2 feet of slack that was in the attic suddenly appeared. I gave him a dirty look, and said nothing. From then on, I never heard one word about leaving "too much slack".

The installer did you no favors by not leaving some slack cable.

Fatman – Wed, 04/15/2009 – 08:51

Comment:  service loop?

Rated: -1

service loop?

Anonymous (not verified) – Wed, 04/15/2009 – 10:45

Comment:  There is a name for that "extra" slack,...

Rated: 3

... it's called a service loop! We frequently hire outside firms to come in and do installation and integration work, and in the contract we always specify that there be service loops of all equipment and patch panel connections. This prevents undue stress on the cables, and also allows you to remove a connector without unlacing an entire rack when something eventually breaks. I will require installers rip out and redo a wiring job to provide adequate room to work in a rack.

CAPTCHA: GIVBUG - what two year old boys and teen aged hackers delight in doing!

HappyFish – Wed, 04/15/2009 – 10:58

Comment:  Neatness Counts

Rated: -1

Yes, neatness does count. However in the patch panel situation the ide is one side is wired in between the panel and the CUs. These never move and can be trimmed as neatly as wanted. The other side of the pane is like a phone switchboard where cables can be moved from port to port. They can be very neat and tidy right uo to the panel but at some point they have to be loose and slack (only an extra foot or two depending on the size of the panel.
BOBV -- Known to lovers of classic rock

Sphynx – Thu, 04/16/2009 – 07:52

Comment:  Cable Installers

Rated: 2

Too many network cable "installers" are just phone techs or electricians eho took a 2hr (if that) course on netwrok installation.

They come; they install; they go; and leave it to IT to make it all work.

Oh well, keeps me busy

Feign – Wed, 04/15/2009 – 11:41

Comment:  Even simpler wiring

Rated: 1

The utility company I worked for before retirement had an old building with an open floor plan with cubicles all over the place. All the wiring , power telephone, and data were in troughs in the floor. There was a spaghetti of coax serving 3270 data. Each time a change was needed, we had to get the company's Utility Construction and Maintenance Department (UCM: the people who built substations and their controls) to come in and string (or subfloor) the coax. That was time taken from their primay duties and had to bescheduled when they were free. No coax was removed in the process.

Somewhere in time, our telephone contractor, whose cost per hour was WAY less than skilled UCM people, and who did everything for us from PBX the desktop came up with an idea. They were already running 8 pair station wiring for the desk phones. Why not use similar wiring for the 3270 as well, using coax to UTP baluns? Cheaper, simpler, faster, and not as sensitive to impedence variations as from crushed cable, for example.

I could not find the specific baluns we used in a search today, I found that prices for these things range all over the place. On e-Bay today, someone is selling them for $3.00 each but they range on up to nearly $60.00 singly. I don't see a reason to spend on the high end for this purpose.

I realize that this is after you have completed your installation but perhaps it is food for thought for the future.

mcherr – Wed, 04/15/2009 – 11:48

Comment:  hide the loop

Rated: 3

well done! neatness is visible, maintenance is at the mercy of the installer. a 'service loop' is required for just what it means. having been 'sentenced' to being an installer, between gigs, I insist on just enough to reach from 'where it was' to where 'it might go later' a concept lost on most wiremen. we use removable ties
every foot which can be loosened with a fingernail and then retightened after the bundle has been modified. the original 'look' is for prompt payment: wow! the first thing I do when a problem or a modification arises is to rip it open and ignore the resulting mess. the electrons don't care about 'dress'.
the proper procedure at the beginning of an install is to assign a rack for video and a rack(s) for audio and built outwards from there. 'ins' go 'out' to the sources and 'outs' go to the next in the chain(s). do any of you know the difference between half and full normal ?

jonesy – Thu, 04/16/2009 – 10:01

Comment:  Service loop

Rated: 2

Here's another reason for a service loop - it keeps the rain from running into the switches. My wiring closet is on the 2nd floor of our 15 storey mouldering building. When we get a good rain, the water seeps from the roof down through the elevator shaft and also through the wiring closets on each floor. I have my paper towels taped tightly around the cables running down the wall, just above their junction with the router, and I've put a sheet of plastic over the UPS and Cisco router. Nonetheless, it is the slack, the service loop, that ultimately protects the equipment. In case some water seeps past my hokey dams, the service loops insure the drips fall to the floor rather than run into the ports.

Anonymous – Fri, 04/17/2009 – 10:40