How to Choose Cables for Power Over Ethernet?

How to Choose Cables for Power Over Ethernet?

Posted on by FS.COM

Power over Ethernet (PoE) is a technology that allows network cables to carry electrical current to power devices rather than by power cords. From late 1990’s, PoE has been widely used since it’s a reliable and cost-effective solution to provide both data and power over a single cable. Then what kind of cable is suitable for your PoE devices? The following content will tell you how to choose cables for Power over Ethernet.

Cat Cable for PoE

Power Over Ethernet Standards

Power over Ethernet allows devices to be powered over 4-pair category cables. And the delivered power might be up to 100 watts. The IEEE standards 802.3.af and IEEE 802.3.at has ratified first two types of PoE. The power sourcing device compliant to these standards deliver the power of 15 watts and 30 watts. Usually lower power devices apply these types of PoE, such as IP telephones, wireless access points and some cameras. Later the IEEE 802.3.bt developed two new standards for higher power delivery. These two types can offer power up to 60 watts and 100 watts respectively. The new PoEs can create more heat within the cable compared to the former two kinds. If the generated heat can’t be managed well, the whole system will be damaged. As well known, not all cables are constructed to be able to safely support the high power in the installation configurations. Thus, you have to consider several factors to ensure the cables suit your PoE devices.

Factors to Consider

Due to the high delivered power, close attention should be paid when picking the cable for PoE. Choosing the right cable is the key to the network quality and reliability. What factors should be concerned for buying cables?

Conductor Size

Conductor resistance in PoE applications results in heat generation in the cable. Typically, Cat6 and Cat7 have larger conductor size than Cat5e. Cables with a larger conductor size can reduce more conductor resistances. It’s said that the heat generated in the cable will be reduced with the same ratio of the conductor resistance reduction. Cat6 cable has about 80% heat generation of Cat5e cable. Thus, the larger conductor size of the cable, the better.

Cable Structure

Cable construction is also a factor leading the temperature rise of a cable. Copper cable can be divided into UTP (unshielded twisted pair cable) and STP (shielded twisted pair cable) cable based on cable structure. Usually cables with metallic or foil shields are proved to dissipate more heats than UTP cables. Higher heat dissipation leads cooler cable. When using Cat6 F/UTP cable, more than 40% heat can be dissipated compared to Cat6 UTP. If allowed, choose Cat7 S/FTP cable with a foil shield around each pair which can dissipate more heats than Cat6 and Cat6 F/UTP.

Cable Temperature

Cables with high temperature ratings allow for a higher amount of power to be dissipated. Typical temperature ratings for cables are 60°C, 75°C and 90°C. If the temperature of a cable rises, the electrical performance will be degraded. And it’s not good for the cable’s physical performance and longevity. According to researches, shielded cables are less likely to be affected by temperature that UTP cables.

Installation Configuration

The last factor is the cable installation configuration which has a large effect on the heat dissipation ability. Heat will be kept within the cable as high thermal resistance and high conductor temperature occur with large cable bundles or other installation factors. The larger the cable bundle size, the higher the temperature, no matter what cable category and construction structure.

Conclusion

Power over Ethernet has many applications, for example, IP camera, wireless network, etc. To some extend, whether PoE devices can operate well depend on four parameters, including cable conductor size, cable structure, cable temperature ratings, installation type. FS.COM provides PoE switches and PoE media converters for your PoE applications. For your convenience, we also offer high quality Cat5e, Cat6, Cat6a and Cat7 cables with shielded or unshielded type. If you need to build PoE connections, get what you need from Fiberstore or contact us via sales@fs.com.

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