Power over Ethernet (PoE) is great for supplying electricity to a variety of networking, AV and computing devices – any device connected to the network – without an electrical outlet or adapter. It also reduces the complexity and the amount of building materials required to power and connect a device to the network by allowing a single cable to provide both services – data and power.
What is PoE?
over Ethernet (PoE) is a technology that lets network cables carry electrical
power as well as data.
For example, a digital security camera normally requires two connections to be made when it is installed:
A network connection, in order to be
able to communicate with video recording and display equipment
A power connection, to deliver the electrical power the camera needs to operate
However, if the camera is POE-enabled, only the network connection needs to be made, as it will receive its electrical power from this cable as well.
Why use POE?
Specifying Power over Ethernet brings many advantages to an installation:
Time and cost savings – by reducing the time and expense of having electrical power cabling installed. Network cables do not require a qualified electrician to fit them, and can be located anywhere.
Flexibility – without being tethered to an electrical outlet, devices such as IP cameras and wireless access points can be located wherever they are needed most, and repositioned easily if required.
Safety – PoE delivery is intelligent, and designed to protect network equipment from overload, underpowering, or incorrect installation.
Reliability – PoE power comes from a central and universally compatible source, rather than a collection of distributed wall adapters. It can be backed-up by an uninterruptible power supply, or controlled to easily disable or reset devices.
Scalability – having power available on the network means that installation and distribution of network connections is simple and effective.
Devices that use Power over Ethernet
POE has many applications, but the three key areas are:
VoIP phones – the original POE application. Using POE means phones have a single connection to a wall socket, and can be remotely powered down, just like with the older POTS or plain old telephone system.
IP cameras – PoE is now ubiquitous on networked surveillance cameras, where it enables fast deployment and easy repositioning.
Wireless – Wifi and Bluetooth APs and RFID readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.
Myths and misconceptions
Compared to Ethernet, PoE is a recently-developed technology, and many people are put off adopting it by the raft of conflicting or out-of-date information that is available on the subject. Here are the most common misconceptions:
PoE has compatibility problems. Not so. It is true that the early days of POE, many home-brewed and proprietary schemes were employed to get power over network cables. However, the IEEE 802.3af standard has gained universal adoption as POE’s popularity has spread, meaning that compatibility between all modern POE equipment is assured.
PoE requires electrical knowledge. Again, early ad-hoc implementations may have required careful design, but IEEE 802.3af POE is designed to ensure reliable operation in any configuration that would be possible with regular Ethernet. All the user has to do is wire up the network as normal, and the equipment will take care of power delivery.
PoE requires special wiring. Not at all, the same cabling – Cat 5e, Cat 6, etc – and “RJ45”-style connectors are used for both regular and PoE-enabled local area networks.
Power is forced into devices. This misconception is surprisingly common; however, it is important to remember that power ratings quoted by manufacturers are upper limits and are not fixed. Plugging a 5-watt camera into a 15-watt injector does not result in 10-watts of power being lost somewhere; the camera will simply draw as much electrical power as it needs.
No longer confined solely to VoIP phones and security cameras, more types of powered devices are beginning to call for Power over Ethernet connections. And these devices are requiring higher power levels, too. Wireless Access Points, digital signage, videoconferencing systems and laptops are all increasing the amount of power running through cables. In fact, the latest PoE standard, IEEE 802.3bt, 4PPoE published in September 2018 introduces two additional power types: up to 55 W (Type 3) and up to 90-100 W (Type 4)
But higher power levels running through a cable can cause performance issues – namely by making the cable hotter. And when the cable gets hotter, insertion loss increases. This escalates your chances of your business experiencing a productivity reduction – and may also damage the cable itself.
The type of cabling you select 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 the consensus is clear: You’re better off using Category 6A for a number of reasons we’re going to cover here.
1. 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 better performance will provide 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.
2. Less Power Loss
Energy efficiency increases when structured cable maximizes the power running through it to waste as little as possible.
As we mentioned above, losing nearly one-fifth of the total power in a 24-gauge Category 5e cable may seem like a lot of power loss – and it is. But doing the math will show you that the total dollar amount comes out to be only around $7 per year. The numbers start adding up; however, when you realize that it costs $7 per year per PoE device across your entire facility or campus – from surveillance cameras to wireless access points. Although it may seem like a small dollar amount when viewed out of context, power dissipation through a cable can ultimately lead to higher-than-necessary operating costs.
It’s also important to keep in mind that the number of Power over Ethernet devices is only going to increase in your facility as you install more wireless access points to support things like BYOD (bring your own device). As a result, you’ll need more PoE cable – and there will be more opportunity 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.
3. Tightly Packed Cables
If your cables are tightly packed in their trays and pathways, the chance for heat increases because it doesn’t have a chance 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. (This doesn’t apply to all Category 6A cables. Even though they promise a 100 m solution, some cables may become an 85 m solution if the temperature increase is too high.)
Selecting the correct Ethernet cable for deploying Power over Ethernet solutions is critical for reliable and effective systems. PoE bring many benefits to deployments as it can be a significant way to reduce initial spend and increase reliability.
With tens of thousands of kilometres of cables deployed connecting countless devices let PTC assist you with your next PoE buildout.