Issue link: https://www.e-digitaleditions.com/i/1066130
22 I ICT TODAY Insertion Loss (dB) at 100 MHz Insertion Loss Temperature Profiles Temperature (˚C) 26 24 22 20 18 16 14 10 20 30 40 50 60 70 Cat 5e UTP Limit Cat 5e Shielded Limit Cat 5e UTP (24 AWG) Cat 6 UTP (23 AWG) Cat 6A UTP (23 AWG) Cat 6A F/UTP (23 AWG) Cat 7 A S/FTP (22 AWG) FIGURE 3: Insertion loss profiles of category cables when transmitting power. ICT system designers should be aware of how to layout a zone cabling topology so that the zone enclosure is strategically located to service its coverage area. The size of a coverage area can vary depending on the device coverage areas and number of devices expected to be supported. However, as WAPs and other building systems may be supported by zones, the radius of the EO coverage area should not exceed 13 m (43 ft), which is equivalent to the following shape dimensions in two different layout formats: • Square—not to exceed 18.4 m (60 ft) length or width. • Hexagonal—not to exceed 22.5 m (75 ft) length by 19.5 m (65 ft) width. Refer to ANSI/BICSI-007 or manufacturers' specifications to help with the layout of a zone enclosure topology. THE HEAT IS ON Whether the topology is centralized or decentralized, one of the main concerns, especially with running remote powering above 60 W, is heat build-up within cable bundles (see Figure 3), as well as the potential for electrical arcing damage to the connector contacts supporting remote powering applications. Although Type 3 and Type 4 PoE (60-90W from the PSE) is not significant enough to cause cables to melt or conductors to short, internal temperature rise within bundled cables increases insertion, power and efficiency losses, which may require the overall channel length to be reduced. ICT system designers should refer to the NEC 2017, TIA-TSB-184-A and ANSI/TIA-569-D-2 for safety and design practices for best cable performance and sizing of pathways. These documents focus on defining acceptable temperature rise as it relates to the bundle size, conductor size (AWG), ambient temperature and insulation temperature ratings. In addition, these documents provide best installation practices to ensure optimal cable performance for both data and power. NFPA 70, better known in the United States as the National Electrical Code, added a new section, NEC 725.144, that provides an ampacity table outlining the maximum number of cables and associated bundle sizes for remote powering applications greater than 60 W (e.g., Type 4 PoE). NEC 2017 also identified a new classification of cable, known as Limited Power (or LP). An LP rating carries a UL-tested temperature rating of the cable properties (jacketing and conductors). Determination of the UL-rating includes powering all the conductors in a large, tightly packed bundle in conduit (insulating the ends of the conduit to prevent heat escape) and adding Temperature (˚C) Subtract 18 m at 60 O C Subtract 7 m at 60 O C Subtract 3 m at 60 O C No De-rating up to 70 O C Insertion Loss Length De-Rating (m) 24 22 20 18 16 14 12 10 8 6 4 2 0 20 30 40 50 60 70 TIA-ISO/IEC Category 6A UTP (minimally compliant) TIA-ISO/IEC Category 6A F/UTP (minimally compliant) Category 6A UTP qualified for mechanical reliability up to 75˚C (167˚F) Category 7A S/FTP qualified for mechanical reliability up to 75˚C (167˚F) FIGURE 4: Channel length de-rating due to heat rise.