Is PoE Safe? The Answer is Yes!
Last month, along with BICSI and Cisco, I participated in a roundtable discussion as part of NSCA’s Pivot to Profit Virtual event. Representing the Connected Technologies Industry Consortium, we discussed recently proposed legislation that may limit power-limited installers’ abilities to legally do work they’re likely qualified to do (install Power over Ethernet cable).
There’s never been a better time to openly discuss this topic. Internet of Things (IoT) is the fastest-growing technology trend in our industry right now. It’s bringing smart buildings to life, supporting manufacturing efficiency, improving energy efficiency and security in schools, and enabling better healthcare.
By 2025, more than 75 billion devices will be connected as part of the Internet of Things. And most of these devices – from wireless access points and white noise systems to meeting room automation and access control systems – will be connected using Power over Ethernet (PoE) for one simple reason: It eliminates the need for these devices to have separate power and data connections.
Instead, delivery of power and data is possible through a single category cable using PoE. This technology moves us from power and data to power with data.
PoE has been around for years (since 2003, when it was first introduced). Back then, the amount of power being supplied through a cable was about 15W. Today, that number is approaching 100W: enough to power laptops and TVs.
Due to this increase in wattage, we’ve also seen a major increase in proposed legislation that, if interpreted incorrectly, could require someone to need an electrical license before they plug in PoE ports or pull and install PoE cable.
If this were to happen, it would be very difficult for power-limited integrators (low-voltage installers) to install or integrate any technology that requires the installation of PoE cable. The only way to avoid exclusion? To become a licensed electrician in each state where work is being performed.
Why PoE Is Safe
For the most part, the purpose behind this legislation is to keep people safe; however, assuming that PoE is dangerous is simply incorrect. Most people already interact with PoE every day, whether they’re connecting a VoIP phone to the wall or using a display in a meeting room. (Even plugging in a VoIP phone has the potential to violate some of the new legislation we’re talking about.)
Because of the way it works, PoE is built to be inherently safe:
- A MagJack in the switch combines and separates data and power.
- The power sourcing equipment (PSE) that provides power on the cable (like a PoE switch) must experience a “handshake” with the PD (powered device or endpoint device) before any power is delivered. This handshake determines how much power the PD needs.
- If there is no PD connected or no handshake between the PD and PSE, then no power is delivered. There needs to be a connection first.
- Once the connection is established, the PSE constantly monitors the amount of current being sent. If the current goes too high or too low, the PSE immediately shuts down the flow of power.
This is much different than how an AC power receptacle on your wall works. There, power is being supplied 24/7, regardless of whether a device is connected (which is how electrical shock occurs).
Putting PoE Safety to the Test
The real question isn’t: “Is PoE safe?” Instead, it’s: “How much power can safely be delivered from the PSE to the PD?” That answer depends on the temperature rise in the center of a cable bundle.
To provide even more reassurance that PoE is safe, we conducted our own controlled (and very extreme) experiment. In fact, the conditions we created in this experiment wouldn’t even be possible in real life.
After visiting a home-improvement store to obtain 90 m of a residential-grade, Category 5e cable rated for 60 degrees C, we looped it into a bundle and tested it for permanent link performance.
After that, we placed the looped cable into an oven set at an ambient temperature of 85 degrees C – far above the cable’s rated temperature of 60 degrees C. We then added current to the bundle (more current than is possible with today’s technology), creating a 15-degree C rise over the ambient temperature in the center of the bundle.
From there, we let the cable sit in the oven for one hour to see how it held up, checking often for smoke or flame (which there wasn’t).
After letting it cool, we tested the cable again. It still passed performance ratings, which is just another testament to how safe PoE is. If we follow the codes and standards put into place around PoE cable, there are no safety risks.
NOTE: Please do not think that cabling should ever be used in this manner. Use of cabling above its rated jacketing temperature can (and will) change the chemical compounds in the jacketing material, impacting its flammability/fire resistance rating. In other words, don’t try this at home!
Where to Learn More
When safety is a concern in regard to PoE installation, we recommend that power-limited integrators take advantage of the training offered by accredited parties such as BICSI, as well as obtain certification from the manufacturer(s) they work closely with, such as Belden’s PartnerAlliance program.
Belden’s power-limited integrators go through rigorous education from our in-house engineers and designers so they’re prepared to safely handle new technology like PoE.