Fieldbus & Industrial Networking


Why Power over Ethernet demands CAT 6A cable

February 2017 Fieldbus & Industrial Networking

Power over Ethernet (PoE) is ideal for supplying a variety of networking, AV and computing devices without the need for an outlet or adapter. It also reduces the amount of building material required to power and connect a device to a network by allowing a single cable to provide both services.

No longer confined solely to VoIP phones and security cameras, powered devices are increasingly calling for PoE connections; and these devices are requiring higher power levels. Wireless access points, digital signage, videoconferencing systems and laptops all require an increasing amount of power running through their cables. In fact, a new PoE standard, IEEE 802.3bt, supports up to 100 W of power per cable.

However, higher power levels running through a cable can cause performance issues by making the cable hotter; and when the cable gets hotter, insertion loss increases. This increases the chance of a business experiencing productivity-draining downtime and may also damage the cable itself.

The type of cabling selected can make a major difference in terms of how heat inside the cable is managed, as well as how it impacts performance. Category 5e and Category 6 cable can be used to support PoE devices, but Category 6A is preferable for a number of reasons.

Larger gauge diameter

A cable that offers a larger conductor diameter can reduce resistance and keep power waste to a minimum because it has a lower temperature increase compared to smaller gauge Category 5e and Category 6 cables. This superior performance provides additional flexibility, including larger bundle sizes, closed installation conditions and higher ambient temperatures. For example when comparing 23-gauge and 24-gauge cabling, there is a large variance in how power is handled. As much as 20% of the power through the cable can get lost in a 24-gauge Category 5e cable, leading to inefficiency.

Less power loss

Energy efficiency increases when structured cable maximises the power running through it in order to waste as little as possible. Losing nearly one fifth of the total power in a 24-gauge Category 5e cable is a substantial loss. However, although the total monetary amount is only about R75 a year, the numbers start adding up when applied to every PoE device across an entire facility or campus – from surveillance cameras to wireless access points. Although this may seem like a small amount when viewed out of context, power dissipation through a cable can ultimately lead to higher than necessary operating costs.

It is also important to keep in mind that the number of PoE devices will increase in a facility as more wireless access points are installed to support services such as ‘bring your own device’ (BYOD). As a result more PoE cable will be needed and there will be more potential for wasted energy.

Less power is dissipated in a 23-gauge Category 6A cable, which means that more of the power being transferred through the cable is actually being used, improving energy efficiency and lowering operating costs.

Tightly packed cables

If cables are tightly packed in their trays and pathways, the chance of heat buildup increases because it does not have an opportunity to dissipate away from the cable. Some Category 6A cable has enough insertion loss margin to handle the extra heat generated from tightly packed cables without impacting performance. However, this does not apply to all Category 6A cables. Even though a 100 metre solution is promised, some cables may become an 85 metre solution if the temperature increase is too high.

Belden 10GXS cable can handle the added heat while maintaining its full 100 metre performance. This is the only Category 6A cable that can make this claim

For more information contact Greg Pokroy, Jaycor International, +27 (0)21 447 4247, greg@jaycor.co.za, www.jaycor.co.za





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