Subscriber Discussion

Electrical Interference In Warehouse Installation

I could use some advice on this one.

After exclusively dealing with residential projects only, I am now facing the next somewhat daunting step….my first full-fledge commercial project. The scale of the project does not bother me (~25 PoE cameras), but being that this is a rural, unconventionally built warehouse with HVAC equipment, refrigeration units, pumps, voltage panels, and even a VHF antenna on the roof, I’m a little apprehensive about the electrical interference factor.

I have read every article & discussion on IPVM along with other articles on the internet, but I still can’t quite pinpoint to what extent I should worry about shielding. Proponents of STP state its necessity, but then I read that STP can also be a detriment ("STP vs UTP for Surveillance"). Others say that using Cat6 cable would suffice, but others claim Cat6A in needed due to the added twists ("Cat5 Vs Cat6 Vs Cat6A Vs Cat7?"). I also read the discussion titled “Should All Security Wiring Be Run In Full Conduit?”, but there was no definite yes or no. Of course, I will take the precautionary measure of not running my cabling along side of electrical lines or next to large equipment, but in an environment like this one, there is stuff to avoid (to some degree or another) around every corner.

So, to what extent do you guys really worry about interference? Am I overreacting due to my lack of experience? Is a good quality Cat6 UTP enough? Although I realize it is tough to comment without knowing the specifics of the project, I would greatly appreciate any input.

Boy, do I ever appreciate your input Ari.

This puts my mind more at ease, since I thought for sure this would warrant some EMT. Although my motto is better safe than sorry, it looks like I'm worrying way too much about interference. I still have to use PVC conduit in many areas due to possible cable damage by daily operations, but PVC is much friendlier than EMT.

Many thanks. :o)

Crossing electrical cables rarely if ever causes measurable issues. It's running parallel with electric cables that could give you problems. Knock some drive rings in the center of the rafter to keep your lines as far from the electric as possible, one drive ring every four feet or so, and loosely secure them with tie wraps tied to the drive rings (don't tighten them or you'll have a whole new set of problems. Done.

Thanks for the replies.

If I can be a bit more specific, I'd like to get some input for the scenario pictured below. If I can get a sense of what is needed here, then I can figure out the rest. First, I have already tried to find alternative paths, but there is no better way around this. I need to get my Cat6 cable down the rafter and out the opening in the background. FYI, the large PVC conduits feed the electricity to a large industrial equipment room. I would like to stick with running just Cat6 UTP, but if this scenario requires metal conduit or STP, then I'm pretty much committed to using it everywhere since there are varying levels of this condition around every corner.

Crossing Multiple Electrical Lines

Hello Jerome:

Thanks for linking to all those articles!

Ari offers some good pragmatic advice here.

I am not suggesting this is academically correct, but here is how I chose when to use Shielded cable or not:

1. What does the manufacturer tell me? Does this vendor give me guidelines when/when not to use shielding? Some manufacturers are very explicit in defining when/where shielding should be used (eg Axis: Is it outdoors? Then use STP), and they can point to an installation nonconformity as 'an out' during troubleshooting or even warranty issues.

2. How close is my cable to a source of interference? (ie: machinery, light fixtures, big deltas in electrical distribution) If my cable is running atop florescent light fixtures, I weigh the cost of shielding vs. (re)running cable using bridle hooks 3' - 4' away instead.)

With that said, typically STP wasn't used until troubleshooting began. If a camera returned poor video, and it was confirmed to NOT be the camera's issue, then rerunning shielded cable between the camera and switch was worth trying before ripping out a switch or spending tons of hours with a camera, server, or VMS manufacturer.

Good quality Cat6 is enough, if your equipment is properly grounded and isolated. Ground all your networking equipment, ground the server or NVR, and run everything through UPSes. That'll eliminate or mitigate almost all possible sources of interference. Worse case scenario, you may have to ground the cameras themselves.

And stay away from power lines and light fixtures, especially fluorescent lights. Four feet or so should be enough. You can cross a BX or Romex if you must, but don't tie-wrap to or run in the same chase as power lines, and try not to run comm lines parallel to electrical lines, either (unless you're more than 4 feet away, in which case, go nuts).