There’s a lot of discussion around horizontal support for low voltage or unstructured cables. It’s a fundamental component of any data network. However, vertical cabling solutions get somewhat less attention. In fact, a quick search of the internet will reveal that most vertical cable support systems are designed for structured or high voltage cable. The National Electrical Code (NEC)  provides guidance (specifically in Article 300.19) for most vertical applications and this article is not meant to supersede the NEC specifications — consult with a licensed electrician if you have questions about how best to support your vertical cables, structured or unstructured.

This article will cover some of the reasons for that disparity. 

Going Vertical With Data Cable

First of all, many horizontal cable raceways can be repurposed for vertical installations. Data cables can be easily anchored to the raceway every 3-4 ft without excess strain or deformation. This type of data cabling application, where cables traverse between floors, such as in a multi-floor office building is referred to as backbone cabling and requires proper planning. Imagine the number of cables required to support a 100-story building!

Because backbone cabling supplies equipment rooms (or server closets) on each floor, the requirements are different than for horizontal cabling. Due to their high bandwidth, fiber optic cables can reduce the number of cables required in the backbone while offering peak performance all the way up to the top floor.

Why Vertical Cable Supports Matter

Now, if you’re actually installing structured, power-supply cables, the need for vertical supports is quite different from data cables. Power cables run through conduit and are rarely exposed in the same way that data cables are. This means that you may have long spans of cable running through vertical conduits without any support. Power cables are much thicker and heavier than data cables, so an unsupported power cable will pull significantly on the upper terminal until it fails. The NEC provides guidance for how power conducting cables should be supported in vertical installations, and while it doesn’t explicitly cover data cables, the same rules do, in theory, apply to low-voltage data cables.

Steel-armored cables do fall under a different set of NEC requirements for vertical support and can be clamped securely without damaging the cables inside. In essence, the interlocking steel armor provides continuous support to the cable and need only be fastened properly at the top of the riser.

Types of Vertical Cable Supports

Power cable supports come in two primary types that are suitable for permanent installation. There is a common wire fixture known as wire mesh grips, these can be used in short runs, or temporarily, but they’re unsuitable for long-term support. 

One-piece Plug

The one-piece plug resembles the chamber of an old-fashioned revolver with the outer portion cut away. It’s a circular plug of plastic or rubber with small semi-circles arranged along the outer rim. This plug is designed to have the adjacent cables inserted into the semi-circular openings and the plug pressed down into a bushing — thereby pressing the cables against the bushing or junction opening and preventing them from slipping under their own weight. It’s ideal for unarmored cables carrying 600 V or less.

Multi-segment Plug

The multi-segment plug is composed of interlocking “slices” that can be wedged into a bushing one-by-one until the opening is filled and the cables are properly secured. The end result is very similar to a one-piece plug, but sometimes a multi-segment plug makes for a much easier installation. This type of support is best used for high voltage (+600 V) with softer insulation. 

Installation Tips

Cables can grow very heavy, especially over long distances. It’s important to calculate ahead of time how heavy each cable will be for the span and how frequently you’ll need to install supports. 

Support Methods

1. There are three primary ways to secure conductors to in vertical installations
The insulating wedges (or plugs) we described above. These must be installed in the ends of the raceways and if they do not provide sufficient support, the conductor should be clamped using other acceptable fasteners until it is properly supported.

2. Installing boxes at appropriate intervals so that insulating (wedges or plugs) can be pressed into the bushings and support the weight of the conductors. The boxes should have removable covers.

3. Junction boxes that allow the cable to be bent at 90 degrees and run horizontally for at least twice the diameter of the cable. The cable must be propped up by insulating supports and secured to the junction box. This method does require more frequent placement — not greater than 20% of the interval shown in the spacing interval table (per NEC 300.19(A)).

The Same But Very Different

As you can see, due to the difference in construction and function, data cables and power conducting cables already use distinct infrastructure. Even though they’re governed by the same regulation, you cannot treat them the same way. Running data cables through conduit is rarely advisable, and strapping power cables to ethernet raceways is a recipe for disaster — not least because of the potential for massive attenuation issues in any nearby data cables. 

If you’re unsure of which vertical support solution is right for your facility, it’s best to consult with a licensed electrician or experienced data network installer. Even if your situation isn’t covered explicitly by the NEC or IEEE regulations, you’ll still be able to find an approach that will keep you in compliance and get the best from your cables.