Slightly OT: Data cabling between buildings

[Andy Burns]

I know it is good practice to use fibre for connections between buildings, protection from lightning strikes being one reason, avoiding earth loop problems another, though I suppose cat5 ethernet is differential and isolated (but only by a puny transformer) compared to old thin/thick wire ethernet.

Assuming mechanical protection is good, is there any requirement (as opposed to recommendation) to use fibre as opposed to copper, or any specific requirements which must be followed if copper is used?

[Goonerak]

There is no requirement to use fibre as opposed to copper externally. You can buy cat 5 surge arrestors but they are not cheap. Systimax are the only company I know that make them, available from

How far apart are the buildings that you want to connect? If the two buildings are within 45m of each other, the cable route may be protected by the buildings' cone of protection.

[Andy Burns]

Thanks for that

It's already been done, from what I gather it's a few feet span to a portakabin, my opinion was asked on whether it was best practice, or if it was downright wrong ...

[The Natural Philosopher]

Cat 5 using ethernet technology is only good for a 100m or so, and you need a switch at each end.

More than that, you can use DSL technology and get about 2Mpbs over about a km.

Oherwise, assuming you can keep it dry and protected, no reason not to use copper.

[w_tom]

Protectors are not expensive. Some examples:

?productID=153#spec But the protector is only as effective as its earth ground. The wire entering each building must do as BT has done for generations. Wire must enter building to make a less than 3 meter connection, through protector, to earth ground. Protectors is not protection. Protection is earth ground. A protector is only a device that connects to earth ground during the transient.

Proper earthing means all incoming wires must make a short connection to the same earth ground. Very inexpensive when wire is first installed. Fixing a defective installation gets more expensive.

There is no c> Go>> There is no requirement to use fibre as opposed to copper externally.

[Andy Burns]

thanks

I believe separate earthing wasn't initially done, but since initially questioned the original contractor *has* now installed earthing of the metal conduit used.

Installing protectors sounds cheaper than replacing copper with fibre.

[w_tom]

Earthing is THE most critical aspect of a cable installation between buildings. Not just any earthing. It must be single point earth ground to every incoming wire. Not safety ground; earth ground. Conduits are typically only safety ground. Electricians, trained only in human safety, often will not comprehend the principles of transistor safety.

Connections to that single point ground must be short (less than 3 meters), direct (no splices, no sharp bends, and not inside metallic conduit), and independent (all earthing connections must remain separated from other wires to avoid induced transients and must remain independent of each other until all meet at the single point ground). Some concepts demonstrated in figures from the NIST, industry professionals, and an electric utility:

Protection is not defined by the protector. Protection is defined by earth ground which is why effective protection is so inexpensive when first installed and so expensive to repair later. Even buried wires carry destructive transients into a building; therefore all incoming wires must be earthed to the same single point earth ground.

Its not separate earthing. That NIST figure (in epri-peac.com) demonstrates how separate earthing causes fax machine damage. Single point earth ground. No earth ground means no effective protection - no matter how many £millions are spent on protectors.

Fiber is often recommended by those who never learned how to > w_tom wrote:

[Andy Burns]

From what was described to me, I think that a separate ground earth has been fitted, but will check ..