Shielded cabling

[ForestGump]

I'm currently in a new manufacture plant and we are going to install a 6a shielded copper infrastructure.

The config is as follows

A fiber backbone will run from a sever room MDF to an IDF box mounted on a floor to ceiling column.

The outside columns of the building have been grounded and all supported columns are connected to this outside column structure.

I'm having a 6ga grounding wire attached to the column and then attached that ground wire to an IDF box which will be attached to that column.

A shielded modular patch panel will be grounded to the IDF box inside.

The data cables will be terminated to a 6a shielded jack and the jack will be mounted in the shielded patch panel.

The Data cables will run up the column out of the IDF box to a aluminum spilt Power/low voltage tray.

Each cable will run in the tray to a appropriate column and go down a 3/4 EMT conduct to the floor, across the floor, in EMT conduct, and enter a PLC control panel where it will be terminated with a 6a shielded jack and placed in a box in the control panel. This end will not be grounded.

There are 23 cables that will make up a zone in the factor and there are 3 zones which will be on the factor floor all connected via fiber back bone.

The longest run is 310 feet.

The question-Is the grounding procedure described above; of adequacy?

 

[wires]

I'm having a 6ga grounding wire attached to the column and then attached that ground wire to an IDF box which will be attached to that column."

The idea is a star configuration for electrical grounds. All grounding conductors lead back to the main building ground which is usually at the main electrical entrance. From there all grounds radiate out to the ends of their respective circuits.

When you "re-ground" the IDF box to a column you may introduce a ground loop during an extreme electrical event like a lightning strike. During this transient the column and the main electrical ground could be at different voltages.

This is somewhat nit-picking since the IDF box is most likely metal and the column is metal and by screwing the two together you have probably grounded it as well as the 6 AWG wire you described.

 

[ForestGump]

Thanks for your input.
The electrical contractor has mentioned the building will soon be lightning protected.
The IDF box will be mounted to the column by struts.
In your option should I scrap the paint off the column, leaving strut metal to metal column contact?
Or should I have the electrician weld the ground wire to column and run the wire to the box?

 

[oldtimerbob]

You should have no problem with your install, make sure you have the sheilded patch panel end properly grounded in the IDF.,Most of us run a ground from the rack inside the cabinet to the bus bar ( and from the bus bar to your house ground (either to the main building ground or to the bus in the main electrical cabinet) and then making sure to scrap any paint off from around each of the holes where the equipment attaches to the rack and using bonding screws,insure a good ground in a sheiled cable install.

Your electrical contractor will have the expertise to test the ground at each point.

The 'longest run' of 310 feet for the cable run itself is pushing it a little,but if you watch the length of your patch cords,you may do alright, and it will pass testing.

If in doubt check the specs on sheilded systems (most of the major makers like Leviton, ICC, Amp,etc have installation guidelines for sheilded cabling that will answer most of your questions).

Good Luck,

Has been in the cabling business for about twenty years and is now the Sr PM for a cabling company located in the Los Angeles area.

http://www.globusinc.net

Also a General Class Amatuer Radio Operator.

 

[SYQUEST]

ForestGump,

One item you mentioned is that the ONLY connection the IDF has to the MDF is FIBER. That being the case, you don't have any direct "ground" connection to the MDF room. So utilizing the "building" frame should be fine for the IDF bond/ground. If in doubt check with the AHJ for the project.

....JIM....

 

[ForestGump]

Thanks for the advice Wires, Oldtimerbob and SyQuest.
When writing a thread it hard to cover all the facts and communicate to the members of the group you are asking for help. Such as I failed to mention, the MDF room is 10’ by 15’ has its own isolated ground system, generator powered failure backup, stand alone cooling system and acoustical ceiling. I haven’t figured out the ceiling part yet. I have been told by the IT department their will be one sever and a couple of switches.
I have installed a ladder system with an aluminum rack in this room and will ground it to this independent grounding system. My biggest obstacle is the manufactory floor with all its machinery and EMI concerns. If you have the time to add any other concerns I’d welcome your advice.

 

[oldtimerbob]

Some makers also have special termination jacks for industrial usage.
Check their sites out on the web or contact a rep.

Good Luck,

Has been in the cabling business for about twenty years and is now the Sr PM for a cabling company located in the Los Angeles area.

http://www.globusinc.net

Also a General Class Amatuer Radio Operator.

 

[mforrence]

Consider taking fiber right to the desktop... the huge advantage in your environment is that sheild becomes unnecessary, distance is not an issue and you are immune from any and all RF and EMI interference. Yes, it costs a bit more, but will simply work.
Mike

 

[ForestGump]

Yes Fiber would be a great solution. I did give a fiber solution to the client; however there was a down side to this. A fiber solution would create a weak link to the client’s solution. The media converter would require another 110 voltage run to each drop and the converter itself would or could cause an outage with its failure. They chose the copper solution based on it points of failure. Thanks for advice.

 

[mikeydidit]

If you are talking about from above the ceiling through the tiles, i may have something to add to help you.

I use a short piece of 4" EMT conduit to come through the tiles to a short piece of over head ladder rack. Attach a short section of unistruct. above the ceiling grid (around 12” is fine). Place the (you cut to length you need) 4" conduit and place a unistuct strap to the 4". Place the ceiling tile in place and gently lower the 4" down on top of the ceiling tile. Mark the back of the tile with the imprint of the 4". Move the 4" back out of the way and cut the tile now marked with a perfect circle of the 4". I use 4" press on bushings for these. Attach a short section of ladder rack around 1 foot off the ceiling grid. I usually use a 1 1/4" aluminum angle iron 12" long. Attach the angle iron in the middle of where you want your rack. The ladder rack will come off the wall around 4" to the end of you relay rack.

So now you have a sleeve coming down through the ceiling into a ladder rack that distributes your cabling to either side of the rack. Makes a very nice looking install.

Here is some pictures of what I am describing for me.

Here is above the ceiling

http://www.geocities.com/mikeydidit2007/IMG_0801.JPG

This is connecting two sections of rack together for a total room connection.

http://www.geocities.com/mikeydidit2007/IMG_0807.JPG

Here is the back distributed down both sides. "Not cluttered."

http://www.geocities.com/mikeydidit2007/pic.JPG

Hope this is what you need.


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