Powering Devices Over Ethernet: What You Need to Know

Mark Latz
October 15, 2018
Min Read
Powering Devices Over Ethernet: What You Need to Know

Your building’s low-voltage infrastructure is about to get more useful. The Institute of Electrical and Electronics Engineers (IEEE) has issued a new standard amendment, IEEE 802.3bt-2018, that will make powering devices over ethernet more effective, an approach known in the industry as Power over Ethernet, or PoE. PoE has been around for over a decade, but powering devices over ethernet has recently become more, well, powerful, asendpoint Powered Devices (PDs) havebecome more efficientand cablingable todeliver more power.IEEE 802.3bt-2018 supports Type 4PoE, which can carry90 Watts. Calculating for heat loss, this translates to around 71.3 Watts delivered to PDs, enoughto support laptops and digital displays.

Powering Devices Over Ethernet

Why should you care about Type 4 PoE? Because it may result in:

  1. Less costly technology deployment.
  2. New applications for existing technology.
  3. A new era for the Internet of Things and the development of new technology.

Let’s break these down further:

  1. Your technology deployment may cost less: With Type 4 PoE, it’s possible to power many endpoint devices without an electrical outlet. Take digital signage, for example. One of the limitations of digital signage installation has been that displays require both power and signal. With the 802.3bt standard, instead of having both signal and power outlets, devices only need a signal connection. Installation no longer requires hiring an electrician, but can be done by a C7 licensed low-voltage contractor.
  2. New applications for existing technology: One example of a Type 4 PoE application for an existing technology would be security cameras that are mounted outdoors in colder climates. Normally, these cameras require a heated enclosure in order to function optimally, incorporating an electrical connection. Now, these enclosures can be heated via PoE.
  3. A new era for the IoT: PoE allows PDs to have their own IP address, an important factor in the Internet of Things. As sensors and devices proliferate through smart buildings, each will have to be controlled and monitored through a management system. 802.3bt will expand the types of PDs that can be PoE, encouraging further acceleration of the IoT.

Deployment Recommendations for Type 4 PoE

  1. If you already have network equipment and it provides the earlier PoE types, deploying higher-wattage PoE will require incorporating midspan injectors, an additional PoE power source. As time goes on, network equipment will become available on the market that features the newest types of PoE. Plan on incorporating Type 4 cabling in your next refresh.
  2. Consider increasing your project criteria for electrical power service to the telecom room. Electrical engineers should be aware that telecommunications design consultants will be asking for 6 KW into the telecom room. Telecom room size won't necessarily change, but network switch power supplies will potentially double in size. Mechanical criteria for telecom rooms should not be affected as much, as heat will dissipate at the PD (and somewhat along the cabling).
  3. Deploy LP-rated cables, at least 0.5 amps. The more power you put through a cable, the more heat produced. Cables have temperature limitations. Plastic used as jacketing and cable material can degrade over time if the temperature rating is exceeded. If you bundle cables together (i.e. lay them on top of one another in a cable tray) and put them up into a ceiling, bundle temperatures can reach over 130 degrees. An LP rating guarantees the performance of the cable throughout its specified temperature range, including being bundled. The LP rating was put into the 2016 National Electrical Code, so most jurisdictions should already be enforcing these ratings.

Note that if a facility does not have LP rated cabling, it doesn’t mean it’s in violation of the code — it just means that technically speaking they can’t run PoE Type 4 over those cables. TEECOM’s policy is to specify LP-rated cables. This allows our clients to mitigate comments from inspectors regarding how much power they’re running through these cables, and ensures they’ll be able to safely operate Type 3 and 4 PoE with no issues.

Cost: LP-rated cabling has to be certified through Underwriter Laboratories, and this is an expensive process. Manufacturers will have to pass that cost on to customers, but it is not a significant expense over time. Some of the cable manufacturers waited until IEEE ratified Type 3 and 4. Now that it has been ratified, we’ll begin to see many more cable manufacturers offering an LP-rated cable.With the possibility of powering devices over the network, there will be many more IoT products on the horizon. Keep your eyes peeled. This is the true tipping point for the convergence of building systems onto the network.