Chris Bartholow posted 06 Jun 2002
shielded vs unshielded
First let me say that your site is great. I have been looking for an informative site for the layman and this is the best one I have seen so far. Now that I've done enough brown nosing, here is my question:|
I am on a limited budget running cable in a house that is being built. Is it better to run shielded or unshielded? How far should the cable be from electrical lines to not be effected by them?
Any help would be appreciated. THX
Dmitri Abaimov posted 06 Jun 2002
Thank you for the warm feedback!
Back to your question:
It's not just a co-incidence that unshielded twisted pair cables (UTP cables) represent about 75%+ of the horizontal (station wire) part of structured cabling market globally and over 90% in US. Shielded twisted pair cables (STP, you can find ScTP and FTP abbreviations too) seemingly providing 'shield' from Electro Magnetic Interference (EMI), also require you to follow very strict design/installation rules to deliver the benefit. And not only that - its effectiveness is very dependent on quality of the building's telecommunication grounding system. Simply put, the increased cost of implementation is not balanced out by more throughput, so why bother? Another thing that has to be taken into consideration is: it's nearly impossible to build a prefect shielded cabling system because during its use, there will be obviously times when people will use unshielded patch cords, thus breaking up the grounding circuit and wiping off all the benefits (and extra costs too). The simplest example is a telephone cord which is never ever manufactured shielded.
If this is a residential building by chance, don't even think about shielding!
If you can keep about 1 foot (30 cm) distance between your power cables and communications cables and never terminate those in the same outlet box, you should be fine.
We have a document on the particular subject of separation between power and telecommunications cables. You can get a copy from here: http://www.cabling-design.com/resources/documents/
Dmitri Abaimov, RCDD
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