Your questions answered: Next-generation lighting: the emergence of PoE for lighting and controls

Your questions answered: Next-generation lighting: the emergence of PoE for lighting and controls.

By John Casadonte, Product Marketing Manager, Cree Inc. September 28, 2016

Using Power over Ethernet (PoE) not only cuts installation and commissioning costs, but—more importantly—opens the door to endless building integration options that build upon the idea of intelligent or high-performance buildings. Read answers to questions that were not addressed in the live Sept. 20, 2016, webcast Next-generation lighting: the emergence of PoE for lighting and controls.

Question: Do you have case studies that compare a typical office building with fluorescent lamps versus an “equivalent” power over Ethernet (PoE) application?

John Casadonte: Please see this Quest case study for an example.

Question: What is the 90 W standard distance limitation?

Casadonte: 100 meters.

Question: What is the current technology maximum for a PoE wattage available on a given category cable for a lighting fixture?

Casadonte: A little over 100 W as the Cat-x will likely begin to overheat if pushed further. Expectations that new cable technology will be in place as the PoE standards grow.

Question: NFPA 70: National Electrical Code (NEC) requires complete separation of wiring for emergency lighting circuits. How do you configure your system to provide separation of normal power lighting from emergency?

Casadonte: A separate PoE switch and Cat-x cabling.

Question: How do we guard against obsolescence in cabling when Cat-8 is already on the horizon?

Casadonte: A tough question to address. Historically most data vendors have handled product/technology very gracefully, but we are now facing a tremendously fast ramp-up and it is likely some investments today may be lost as time progresses.

Question: Are the PoE lighting devices more energy efficient than their 120/277 V equivalents? That is comparing LED to LED.

Casadonte: About the same.

Question: Will the egress lighting/emergency be color indicating?

Casadonte: All depends on the luminaire. Speaking specifically on our Cree portfolio, we have field changeable color temperatures. In our case, the answer is yes.

Question: A few lighting vendors are claiming that PoE switches have 3 to 5 years to become a viable solution for lighting power. They are not very effective right now. Is that true?

Casadonte: As stated in the presentation, the 60 to 90 W range is a limit to the number, type, and application (indoor/outdoor) luminaires that can be used. Ethernet switch manufacturers are rapidly re-tooling to accommodate a much expected fast growth rate.

Question: What double redundancy features can we build into these systems?

Casadonte: At this time, the redundancy is centered solely around source power. If the PoE switch loses power it should be configured with an uninterruptible power supply (UPS) or backup generator. This is no different in philosophy as emergency battery backup on a luminaire.

Question: The presentation did not include any of the technical challenges in implementing a PoE powered system for lighting. The benefits of this system are similar to a digital addressable system with 120-V power. The main focus should have been how such a system is implemented and what are the current restrictions and how those will be addressed in the future?

Casadonte: Check out this article by Sandra Gittlen in Computerworld to understand the challenges of PoE.

Question: With regard to safety: Fire might cut or melt the PoE wiring isolating people in islands. Why would you want to use PoE rather than dedicated armored cabling and controls?

Casadonte: Definitely a concern and not to be overlooked in the design and layout of the PoE solution. Options include separating PoE paths, using redundant PoE switches, and even conduit to protect certain feeds of the Cat-x cabling. I do believe this is a challenge for this technology but feel confident it is addressable.

Question: PoE 60 W each device—what is the total per wire?

Casadonte: Each PoE port supports one PoE device (phone, wall switch, luminaire). The standards today do not account for a “multidrop” implementation where more than one device is supported per cable. Additional technology is needed to manage the power consumption in a judicial manner.

Question: Please provide more detail about the capability of PoE switches?

Casadonte: Read this from our technology partner, Cisco.  

Question: What is the efficiency of PoE (i.e., dc line) versus ac/dc conversion of now-common LED ac-socket lighting fixtures? What percent energy loss (copper loss) with PoE when compared to 120 and 277 Vac? Are there voltage loss concerns with PoE? That is, the lower voltage means wire resistance is more consequential. Is there a wire length limitation? Is dc/dc boost circuitry required?

Casadonte: Here is an awesome calculator that can help you understand the efficiency of the PoE port and cable combination of a given distance.

Question: What nominal voltage level is utilized? Are both ac and dc being used? What’s the maximum current?

Casadonte: I think you will find this reference site to be of value:

Question: Does Cisco own this technology?

Casadonte: Cisco is instrumental in pushing the standard.

Question: Industrially, sensor re-commissioning every 3 years is expensive. How often to do these new PoE sensors need re-commissioning?

Casadonte: Lighting vendors selectively source components (i.e. sensors) and the reliability and accuracy levels are taking into consideration in product positioning. If a product incorporates a high-end sensor, then we are dealing with significant price differences that consumers may not be willing to pay.

Question: Is there a battery back-up system that can be built into each fixture?

Casadonte: This is no longer a function of the luminaire, but now is in the hands of the PoE switch and the rules specified in the configuration.

Question: Is there a color coding requirement for the PoE cabling for lighting versus data or fire alarm system, low-voltage Cat-5 and Cat-6 cabling?

Casadonte: No requirement. Likely this will fall into the decision of the IT teams to help easily identify the purpose of a Cat-5 cable’s responsibility when identified in the ceiling/wall/floor.

Question: It seems like there will a lot more Ethernet wiring to power the same amount of lights compared to 277 V system.

Casadonte: Not all PoE solutions will prove a better cost. Size of the installation and coverage areas are factors. Do not forget that labor will be significantly lower with PoE.

Question: Will larger AWG wires be required for Ethernet cables in long runs, or with several devices to power?

Casadonte: Not at this time; Cat-5, Cat-5e, and Cat-6 cabling today use 22 AWG or 24 AWG and, in rare instances, 26 AWG for very short runs.

Question: Comment rather than question: The use of “high-voltage” earlier was misused. While I understand the intent to distinguish the dc voltage of PoE versus the line voltage of traditional lighting (120 or 277 V) these are not “high-voltage.” While the standards vary some, IEC 60038 defines low-voltage as up to 1000 V. NEC defines low voltage as less than 600 V.

Casadonte: Noted and thanks for spelling that out. I will be sure to use “building voltage” instead of “high-voltage” in the future.

Question: Are these sensors just motion/occupancy (infrared) sensors?

Casadonte: Other sensors (gas, temperature, sound) are available as well.

Question: Is the cable that much cheaper if you have to run plenum-rated cable? I’m seeing $150+ for an average of 80-ft runs. Is it one cable per fixture?

Casadonte: Plenum-rated cable has a special insulation that has low-smoke and low-flame characteristics. Plenum cable is mandated to be installed in any “air handling” space. For example, most large office buildings use the ceiling to return air to the air conditioning unit. This qualifies this ceiling as a plenum ceiling, and all the cables that go through that ceiling must be plenum-rated. Please check your local building codes to see if you need plenum cable. The reason why it costs so much more is because the material required for the insulation must meet the standards for plenum cables while also meeting the standards for Cat-5e. This material is relatively expensive.

Question: It seems as though having many building systems run on one type of cabling would create security and downtime concerns, as servers and switches can be subject to failure and intrusion. How are these concerns being addressed in the PoE industry?

Casadonte: PoE attached devices are configured in a virtual local area network (VLAN) with the communication path encrypted to minimize (virtually eliminate) security concerns.

Question: Plans for consumer education and implementation?

Casadonte: PoE is largely considered a commercial application because of the presence of data networking switches that support hundreds/thousands of end points. The consumer/residential market will likely remain ac power as its source and wireless as its communication path.

Question: Talk about greenhouse applications for year-round application.

Casadonte: PoE lighting applications can vary wildly including its usefulness in greenhouse applications. Assuming most greenhouses have open ceilings, a PoE solution really could be ideal with one major caveat—an applicable luminaire.

Question: For high-bay occupancy sensors and fixtures, can you discuss the value of using PoE versus wireless devices?

Casadonte: PoE not suited for high-bay products as they typically exceed power limitations of the PoE switch.

Question: Do PoE switches that power lighting require any special cooling? Typically network switches are in air conditioned rooms or fan ventilated enclosures.

Casadonte: Same level of intention required.

Question: In the IT world where the hackers are increasingly getting smarter at hacking into secure IT networks, how do you see this impact the PoE technology and the ability to control lighting systems reliably?

Casadonte: Specific to lighting, there are measures in place to help minimize threats, but in all honesty, this will have to be handled by the IT staff’s best practices and security policies.

Question: Can solar panels assist PoE without converting to ac current?

Casadonte: The question it to whether solar panels can keep a PoE switch operating.

Question: Do you typically need more racks, bigger IT rooms or separate PoE rooms, additional cooling for separate room, or distribution panels moved from the direct lighting feed to the feed for the PoE switching?

Casadonte: The reality is all of what you wrote are considerations. For example, are you going to upgrade an existing Ethernet switch to PoE or are you just going to run a separate PoE switch? Cost, closet space, and building construction are top-of-mind.

Question: Seems like it would be expensive to retrofit a building or even portion of a building to PoE. Do you have general rules of thumb of what type/size of buildings this would work/be profitable for?

Casadonte: The rule of thumb at this time is not to use PoE in retrofit applications. The financials are tough. Other strategies like wireless controls make more sense.

Question: Are lighting contractors starting to pick this up and start retrofitting buildings to PoE or is this still a very special expertise that only Cree provides?

Casadonte: For new installations, contractors are considering PoE rather than traditional building power. Nothing unique to Cree in this context—it’s really just a business/financial decision by the general contractor or electrical contractor.

Question: Will lighting manufacturers begin to incorporate multiple methods of power connection? For example will manufacturers begin to make fixtures that can be powered by PoE cabling as well as traditional wiring?

Casadonte: This is exactly what we (the industry) have done: Power originated from a PoE Ethernet switch.

Question: Will this system be available for medical offices in the future?

Casadonte: To be very clear, hospitals have restrictions per space and although I haven’t dived deep into areas like the intensive care unit or operating rooms, I feel there will be some restrictions. Common areas like waiting rooms, nursing stations, patient rooms, stairwells, etc. are likely places for installation.

Question: At what point will Cat cable be required to be installed in conduit? 120 W?

Casadonte: Today Cat-x cabling is capable of handling the power without conduit. Higher wattage will likely require a new Cat-y cable.

Question: What cyber security features are available to prevent a hacker using WiFi to take control of the PoE systems?

Casadonte: VLANs, encryption, and password protection.

Question: One Cat cable homerun per fixture?

Casadonte: Yes.

Question: So one light per cable, one light per port in the data rack?

Casadonte: Yes.

Question: Have you seen any pushback for the authorities having jurisdiction (AHJ) using PoE for emergency power to fixtures?

Casadonte: Yes, and there are workarounds, but certainly not as well thought-out as today standards define for building power based solutions.

Question: More PoE switches means larger a UPS, right?

Casadonte: Yes, which needs to be factored in when considering payback.

Question: What is the function of the switch? Is it doing any power conversion from ac power supply to supply to PoE?

Casadonte: Yes, and its main responsibility is data communications.

Question: Have lighting manufacturers made products available to work through a PoE platform?

Casadonte: Yes, many manufacturers now support PoE luminaires.