How the New TSB-184-A Standard Supports PoE
Remotely powered equipment is being deployed in enterprises every day – from wireless access points (WAPs) to IP cameras and phone systems. As these devices play their role in supporting digital building, factors such as centralized powering, power management and backup will become crucial. Based on the locations of these devices, however, providing a close source of local power may be difficult. (An IP camera may need to be placed in a location where no local power source is readily available, for example.)
Twisted-pair Power over Ethernet (PoE) cabling can be used to remotely power a device, solving this challenge and streamlining installation by transmitting power and data over a single category cable.
It’s important to note, however, that a small percentage of the power being carried over the cable is dissipated as heat inside the cabling. Putting cables into bundles can heighten this temperature rise. Cable temperature rise can push cables beyond their rated temperatures, reducing performance and reliability (and possibly damage the cable). Controlling temperature rise will decrease potential cable problems and network performance issues.
The Introduction of TSB-184-A
As part of its standards review process, TIA recently approved a new Technical Systems Bulletin (TSB), developed by TIA Subcommittee TR-42.7: TSB-184-A, Guidelines for Supporting Power Delivery Over Balanced Twisted-Pair Cabling. The guidelines are intended to be an addition to ANSI/TIA-568 infrastructure requirements.
Approved in March 2017, TSB-184-A offers recommendations about twisted-pair cable that supports and supplies DC power and carries data to networked devices in new installations and retrofit applications. It also provides guidelines for managing cable temperature rise and keeping cables operating below maximum temperature ratings.
By following TSB-184-A guidelines, remote power delivery can be provided via a category cable without compromising performance or functionality.
TSB-184-A Specifics
The standard supports power delivery using all four pairs, with up to 1000 mA per pair for a maximum power of 100W. Recommendations included in TSB-184-A focus on:
- Design and installation guidelines for deploying PoE over balanced twisted-pair cabling, from Category 5e to Category 8, including installation conditions that may require special considerations
- Electrical parameters for remote power delivery and reliable data communications
- Recommendations about cable bundling and reducing cable bundle temperatures
- Maximum current per pair under various installation conditions
- Ways to limit temperature rise when using 26 AWG cables
- Recommendations about pair-to-pair DC resistance unbalance limits
TSB-184-A makes specific recommendations such as:
- Leaving cables unbundled to facilitate better heat dissipation – if not possible, small bundles are recommended
- Limiting the number of cables per bundle to 24 to reduce potential temperature rise caused by installation factors, high ambient temperature, 26 AWG cables and higher currents
- Using Category 6A or higher-performing 4-pair balanced twisted-pair cabling for new PoE installations
Preparing Your Network for 4-Pair PoE
As power demands for IP-enabled devices grow, so will the demands placed on your cable – and your network. The current PoE standard, IEEE 802.3at, allows for 30W of power at the source. The proposed standard, IEEE 802.3bt, allows nearly 100W of power at the source. It is expected to become a standard in 2018.
Belden can help you design a futureproof network, making sure it’s ready to support the technology that powers businesses today (and the new technology that will power businesses tomorrow).
About the Author
Ron Tellas is a subject-matter expert in RF design and Electromagnetic Propagation and joined Belden in 2016 to help define the roadmap of technology and applications in the Smart Building. He now takes these experiences to incorporate systems, equipment and connectivity into network solutions. Ron represents Belden in several standards organizations, committees of the National Electrical Code and as a board member of the FMP Alliance. He has a master and bachelor degrees in electrical engineering, a master in business administration and the inventor of 17 US patents. Ron is a proud recipient of the 2024 Harry J. Pfister award for his outstanding and impactful contributions to the Telecommunications Industry.