# Shielded cable.



## LARMGUY (Aug 22, 2010)

cccp sparky said:


> When should I buy the shielded cables?
> 
> If cable hanging above lighting ballasts?
> 
> Now residential construction having the compact fluorescent ballastings. Should I be install the shielded cables?


Being a low voltage guy I use it only when the device manufacturer specifies using it or when I need communication between devices and controllers such as RS485 and Manchester protocols.


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## sarness (Sep 14, 2010)

Unless it is spec'd, you font need shielded cable. Try to stay a foot away from power and other such things, run at 90 degrees to those if needed.


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## cccp sparky (Nov 5, 2011)

I have a shielded wirings. Does this utilizing a green ground screw, or is the screw on corner of a 4 square box okay for the bonding?


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## jeffmoss26 (Dec 8, 2011)

All I can say is ?????


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## JohnR (Apr 12, 2010)

cccp sparky said:


> I have a shielded wirings. Does this utilizing a green ground screw, or is the screw on corner of a 4 square box okay for the bonding?


Are you an apprentice? Your profile says nuclear power electrician. Does that mean you get your electricity from the local Nuke plant? Where are you trying to use this shielded wiring anyway? I am really getting a feeling that you are an apprentice or a handyman trying to pass as a real electrician. 
If not, sorry but that is a strange question IMO.


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## rnichols (Apr 19, 2011)

cccp sparky said:


> I have a shielded wirings. Does this utilizing a green ground screw, or is the screw on corner of a 4 square box okay for the bonding?


Are you talking like cat5? It depends on the cable, the device.. more information would give you a better answer


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## mikeh32 (Feb 16, 2009)

if you dont have the right ends, shielded cable doesnt do much too


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## CoopElec (May 16, 2011)

*ground Screw*

You should always use a green hex head 10-32 ground screw. If not use the cover screw, just make sure you put the wire through the hole behind the screw, so you dont pinch the wire when you put the cover on.






:jester:


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## sarness (Sep 14, 2010)

I don't think the op has any idea as to why.

One job I went to that they had run shielded cable with a grounding type patch panel, (even had a ground wire run and wrapped around the conduit) had the cable jackets under the bonding clamps, completely defeated the purpose using shielded cable.


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## mikeh32 (Feb 16, 2009)

I am really wondering why you guys are using ground screws on shielded cable....

especially since this is in structured cabling. 

I mean i know i am only a dumb c card, but this whole ground screw is new to me


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## sarness (Sep 14, 2010)

Anything I have ever installed and needed a ground, I would run a ground back to the panel and install a ground bar to tap from.

Your mileage may vary as to what other's do.


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## CDN EC (Jul 31, 2011)

Depends on what it's being used for. Some automation gear calls for shielded wiring drained through a resistor but only on one end, while others demand it and have a terminal for it.


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## mattsilkwood (Sep 21, 2008)

Most generally if you have a digital signal you don't need a shielded cable, if you have an analog signal you do.

I will go so far as to say most of the time you can run an analog signal over a non-shielded cable and not have any issues.

I am seeing more and more equipment calling for shielded cable for everything, motors included. The reason being that a lot of new equipment is ran in cable tray and it will cut down on noise. 

I had one machine that spec'd parallell 3 conductor 4/0 shielded for the main drive motor. I don't care if I never see a piece of that stuff again.

There was another contractor putting in a machine where I was at that had to install paralell 3 conductor 500 shielded. I felt sorry for that poor sob.


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## Jamuz (Aug 8, 2007)

Just remember, the trick with shielded cable is to ground only ONE end of the shield. I see alot of amateurs connect both ends and it defeats the purpose and causes ground loops.


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## Speedskater (Oct 2, 2009)

A consultant and author, Henry W, Ott is probably the lead authority on this subject.
http://www.hottconsultants.com/
If you have a lot of time on your hands, you might read his new $100, 875 page book.

Depending on the situation and which expert you read, you might connect the shield:
a] At both ends.
b] At the source end, with a hybrid connection at the receive end.
c] At the source end only.
d] At neither end. (see above book)


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## CDN EC (Jul 31, 2011)

Speedskater said:


> A consultant and author, Henry W, Ott is probably the lead authority on this subject.
> http://www.hottconsultants.com/
> If you have a lot of time on your hands, you might read his new $100, 875 page book.
> 
> ...


I've seen it vary from Schneider Electric stuff (either do not use, or drain on either end with a 470K resistor), to Delta (terminate to specific terminal on both ends) to to TAC (don't use at all for networking) to Johnson (both ends at terminal (IIRC).

It's all HVAC control stuff so finicky at the best of times.


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## Ridge (Mar 25, 2011)

Where I work the engineers designate it to cut down on noise, there are a lot of cable trays and I have used it in I/O drive cabinets and other I/O devices where there are a lot of signal wires going on with low voltage stuff. I've also used it to sheild 24v dc cat 5 from 110v signal wire in the same conduit. The cat 5 had neat rj45 ends with aluminum cladding.


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## Pinoysparky (Feb 23, 2012)

What are the methods used to shielded a cable and what are the benefit?


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## CDN EC (Jul 31, 2011)

Pinoysparky said:


> What are the methods used to shielded a cable and what are the benefit?


Wrap it in tinfoil - a few layers per foot of cable should do, and take a picture of it with your hand visible and the name "Cletis" markered onto your palm.


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## Pinoysparky (Feb 23, 2012)

CDN mini-EC said:


> Wrap it in tinfoil - a few layers per foot of cable should do, and take a picture of it with your hand visible and the name "Cletis" markered onto your palm.



You are fond of making joke. :jester:


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## chewy (May 9, 2010)

mikeh32 said:


> I am really wondering why you guys are using ground screws on shielded cable....
> 
> especially since this is in structured cabling.
> 
> I mean i know i am only a dumb c card, but this whole ground screw is new to me


 
When we do a shielded network the jacks and all cable including patch leads is shielded, we strip back the cable extra long to allow for a generous amount of wrapping of the drain wire onto the tab on the jack. I drill and tap the unloaded panel to screw on a lug for a 6mm earthing wire and drill and tap the rack to attach the earthing wire from the panel somewhere near the RU its taking up to make it look tidy. The doors are also bonded to the cabinet this way with screws and lugs. Usually I will just run a 6mm earthing wire back to the earthing buss bar but sometimes there is copper sheets installed under the linoleum so we peel back a section of the linoleum inside the rack and cut the copper using a multi tool and make a nice origami fold in it and bolt that to the bottom of the rack. We have never had to attach the actual drain wire in the cable to an ground screw.


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