Frequently Asked Questions About Power over Ethernet (PoE)

Power over Ethernet (PoE) is a convenient and cost-effective technology that has revolutionized modern network infrastructure. The growing demand for PoE technology and compatible devices is significant. According to a recent market study performed by Global Industry Analysts, Inc. (GIA), the global PoE solution market is projected to reach $1 billion by 2024. (1)

Implementing PoE into a business network takes careful planning. In response to this, this article will answer some of the most frequently asked questions about this unique technology.

What is PoE?

PoE is a technology that enables the transmission of both power and data to PoE-compatible devices over a single twisted-pair Ethernet cable. PoE relies on the IEEE 802.3af, 802.3at, and 802.3bt standards with power budgets of 15.4W, 30W, and 60W/100W respectively at 10/100/1000 Mbps.

Why should I use PoE?

There are many reasons to use PoE. Power over Ethernet:

  • Saves money
  • Installation is easy and low voltage
  • Has enhanced flexibility and control
  • Is reliable
  • Is safe
  • Is secure

What are some of the applications of PoE?

The list of PoE applications is long. Here are a few of the major ones:

  • VoIP phones
  • IP cameras and PTZ cameras
  • Wireless access points
  • LED lighting and sensors
  • ATMs
  • IP intercoms and PA systems
  • Security card readers
  • IP clocks
  • Thin client computers
  • Digital signage
  • Point-of-sale kiosks
  • Network routers and switches
  • Industrial control systems

How far can PoE travel on a cable?

The standard distance limitation of an Ethernet cable is 100 meters (328 feet).

Can this distance be extended?

Yes. A PoE extender can increase a network’s reach up to 4000 feet (1.2km). This solution is ideal for hotels, shopping malls, business and academic campuses, and sports arenas.

What are the four types of PoE?

The Institute of Electrical and Electronics Engineers (IEEE) has ratified three standards that define four types of PoE. Below is a “snapshot” of the four types of PoE and their attributes.

What voltage is PoE?

IEEE standards delineate PoE voltage between 44 and 57V DC; however, the voltage is most typically 48V DC.

Can a PoE network have both PoE and non-PoE devices?

Yes. PoE does not interfere with normal switch operation; as a result, PoE and non-PoE devices can be used on the same switch. In addition, many PoE switches are designed to automatically disable PoE from the signal for ports that do not support it, thus, making them more power-efficient.

Are there heat rise concerns associated with PoE?

Type 1 PoE (IEEE 802.3af) delivers a maximum of 15.4W, and Type 2 (IEEE 802.3af) delivers 30W. At these wattages, there is a very low expectation of overheating. However, overheating is possible with IEEE 802.3bt Type 3 (at 60W) and Type 4 (100W).

How can I minimize overheating in IEEE 802.3bt devices?

There are five ways to mitigate overheating when using higher wattage PoE:

  1. Use CAT6A or CAT7 cable. 
  2. Choose cabling with a large conductor
  3. Choose conductors with solid metal bodies
  4. Choose shielded cables—either S/FTP or S/UTP
  5. Use small bundle sizes: The larger the bundle, the higher it’s core temperature. If possible, leave the cable unbundled altogether.

Is PoE technology safe?

IEEE 802.3af/at/bt compliant PoE technology is inherently safe. PoE switches and injectors will not damage any network devices, even if said devices are not PoE compatible. Before the power sourcing equipment (PSE) sends any power, it initiates a “handshake” protocol that establishes the amount of power required by the powered device (PD). If the handshake procedure is incomplete for any reason, the PSE will not send power.

In summary, Power over Ethernet is an elegant solution to providing electrical power to network devices. PoE has many advantages while being easy on a business’s budget.

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