The Network Cabling Challenge: NEC Compliance in the World of IoT Devices and PoEGeorge Brooks
To say that we are living in an interconnected world is putting it mildly. Everywhere the number of network devices is multiplying at an astonishing pace – from motion sensors and Power over Ethernet (PoE) lighting in smart buildings to LED streetlights and cameras in smart cities. At the heart of this lies the intersection of IoT devices and PoE technology, which is creating new challenges for compliance.
An example of this burgeoning new territory is how it drove changes to provisions for Class 2 and Class 3 data cables in the NEC. More importantly, it is now driving the traditional Ethernet-based network environment in commercial buildings to a more dynamic PoE-based network environment. This begs the question: Is it possible for low-voltage installers, electricians and Authority Having Jurisdiction (AHJs) to certify that Class 2 and Class 3 data cables will maintain compliance with NEC section 725.144 in a dynamic PoE-based network environment?
NEC Compliance for PoE
Section 725.144 was added to the 2017 NEC to ensure that cables do not exceed their temperature rating when used to carry power. It specifies three compliance options for Class 2 and Class 3 data cables supporting PoE applications:
- Option 1 specifies a maximum input current from Power Sourcing Equipment (PSE) to a Powered Device (PD) shall be 300mA per conductor at 30 degrees Celsius ambient temperature.
- Option 2 specifies a maximum allowable current per conductor based on the cable temperature rating, conductor gauge, number of cables in a bundle, and ambient temperature.
- Option 3 specifies the use of Limited Power (LP) cables which are rated for a specific conductor current carrying capacity.
These NEC compliance options provide stakeholders (low-voltage installers, electricians and AHJs) criteria for verifying compliance. Since the PoE equipment is typically not in place at the time of inspection and can change once the network goes live, stakeholders cannot be certain that compliance will be maintained. But in order to certify cable installations to the best of their ability, stakeholders must make best-case operating assumptions such as:
How do you know if your network cabling will comply and remain in compliance with NEC section 725.144 in a dynamic PoE-based network environment?
- Cables designated to support Class 6 or lower PDs will never be connected to Class 7 or higher PDs;
- What the highest ambient temperature along the cable pathway will be in the future;
- LP rated cables will never carry current that exceeds their current rating.
When assessing these compliance options in the context of best-case assumptions, the probability of non-compliance is much greater. On the other hand, if stakeholders instead use worst-case operating assumptions, the tradeoff becomes either less PoE provisioning freedom and flexibility or higher cable and installation costs.
Structured Cabling for PoE
In the case of non-compliance, the cable can exceed its temperature rating. As the cable temperature rises, the insertion loss of the cabling channel will increase. As the insertion loss increases, the cabling channel electrical length will increase even though the physical cabling channel length is unchanged. Moreover, the attenuation to crosstalk ratio, an important indicator of usable bandwidth for a cabling channel, will decrease. As this occurs, the Ethernet signal may become distorted or the application may stop running on the network links where the cabling channel physical length is close to the ANSI/TIA Standard limit of 100-meters.
Ethernet and power transmission issues will likely be more evident to IT network administrators. However, the long- term degradation of the network cabling physical and mechanical properties will be less evident and, more importantly, irreversible. Over time as higher powered PoE devices are integrated in the network, the degradation could lead to latent Ethernet and power transmission issues. The only remedy may be to replace the cable.
What if you could safeguard against non-compliance with the NEC ampacity table and perform real-time NEC compliance diagnostics?
For low-voltage installers, electricians and AHJs to confidently certify cable installations supporting PoE, they will need assurance in using reasonable operating assumptions that are based on knowing the installed cabling system is capable of safeguarding against non-compliance with the NEC ampacity table – a method similar to the function of a circuit breaker for electrical systems in a home or commercial building.
To maintain compliance with the NEC while also ensuring optimum PoE provisioning freedom and flexibility with a more economical, high quality Category 6 cabling solution, IT network administrators will need the ability to perform real-time NEC compliance diagnostics.
Network Cable Compliance
As the proliferation of IoT devices continues at a rapid pace, it is imperative to keep the certification and compliance process in mind as it relates to PoE technology implementation and advancement. We believe the most optimal, cost-effective way to achieve this – and safeguard the cabling environment – is to perform real-time NEC compliance diagnostics through the structured cabling hardware. NFLEXON is developing a solution to do just this. To learn more, call 855-NFLEXON (855-635-3966) or email us at firstname.lastname@example.org.