Don't Forget Your Wiring BasicsDon't Forget Your Wiring Basics

Whether determining how to provide backup power for your desktop phones or run cable, don't overlook best practices.

When I'm out and about at client installations, I'm often taken aback by how often the basics of power and cabling go ignored.

One case in point is when I was asked to connect SIP phones for approximately 350 users at multiple sites to local power and, in some cases, to local power and PoE ports in the LAN switch. The company's reasoning, "to provide backup power in case PoE failed," didn't make me too happy.

Powering phones locally is never a good idea. Providing local power to phones as a backup means to the PoE switch only increases your chances for trouble. You're putting yourself at risk from a power outage or surge whether you live in Florida, the lightning capital of the United States, or anywhere else. The fact is, more than 80% of all power disturbances and issues occur within the local power infrastructure.

You can minimize the risk that a local power failure will take out your desktop phones for the cost of some dedicated power cable for the phones, more switching (more PoE ports), and, arguably, more cooling. You'll be using two drops instead of one.

If this isn't acceptable, then don't connect local power to the phones and do install PoE managed switches. Using the phones means you'll still blow out NICs or ports on the phones – end of story. Well, not quite.

In the closet, go the extra mile and install a UPS for the LAN infrastructure. The battery backup should be sufficient for most power disruptions, which typically last just seconds or a few minutes at most. If your business requirements specify the need to be able to power everything for hours or days, then install a flywheel or a generator.

I also see installation best practices routinely overlooked when it comes to the use of outdoor cabling. At one site, for example, security camera PVC cable bundles ran in exposed soffits. As a policy, I told the contractor that any new cabling exposed to outdoor elements needs to be outdoor-rated, and that includes cabling in soffits. Salt air, as was the case here, will wear down the cable.

This best practice applies even for camera drops that exit a building a few feet in conduit to the outdoors; again, it's best to install outdoor-rated wire. This doesn't mean indoor wire won't work; it means the best practice is to use the proper materials in the intended environment.

I made a similar recommendation in a case in which overhead conduit exited a building, turned down to underground, then went back up again to the next building. The contractor had used CAT5e cabling to connect multiple buildings in this manner. I recommended that the CAT5e cable be replaced by outdoor fiber, since lightning and power disturbances will not traverse fiber like they will with copper.

An alternative is to add protection and grounding. The trade off is lower cost but greater risk. Can you live with that?

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