POE Lighting

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Maybe they are running 100 VA in 30 conductors simutaneously.
No, I got deep enough into the marketing speak to see where it says 300W per pair of 18 AWG wires. Then it says "NEC Article 725 / CEC Rule 16-200 Wiring Methods, Class 2 wiring practices (No Conduit, etc)" which is not very specific.


Cheers, Wayne
 

dfmischler

Senior Member
Location
Western NY
Occupation
Facilities Manager
I run POE in my workplace, and at home, but only to power telephones and cameras and WiFi access points and similar devices that need ethernet connectivity.

The previous comment on significant residential market penetration for POE lighting ignores the fact that serious POE switches use a lot of power, and need a lot of cooling. The fans are loud, and the existing crop of switches need to be in temperature and humidity controlled environments. Where do you put such a switch in a home?
 

cvillej17

Member
Location
Pittsburgh
Occupation
Technical Advisor
To me, it'll be a unique solution every time that depends (at least somewhat) on the level of integration/technology of the other systems in a house. There may very well be a data closet that houses other systems like A/V (lots of heat) and security that have similar requirements. To that end, if the space is designed correctly, the issues can be mitigated, just like in a commercial application.
For smaller residential projects, a case could be made for using Cisco's CDB switch which is designed for lighting applications (60w/port), is passively cooled, and is plenum rated. Also, no fans means dust isn't a factor. In the Sinclair Hotel, CDB switches were used for the guest rooms to kill the noise, limit the cost (8 ports vs 24, under $1000), and eliminate the need for a full data closet/rack.
 

Flicker Index

Senior Member
Location
Pac NW
Occupation
Lights
UPSs exist and people buy them to mitigate the effects of a power outage. I'll bet in every instance they've checked to see if they'd rather use (or are allowed to use) a diesel generator that requires testing every month and decided a UPS is a better solution. What's your point?
My second paragraph to Rock86 was a description of the node that runs a PoE fixture. Did you miss that section when you replied to me initially? Sorry you spent time laying out your flashlight knowledge and such, but I said there is no AC driver. There is a DC driver. It's called a node in several of the PoE systems on the market. Each node is custom programmed to tailor the current to the LED array. It is precisely an external LED ballast with an RJ45 connector. Here is a picture of an LED array for a PoE fixture. Pretty straight forward (and HE Williams has nearly 1000 different PoE light SKUs built exactly the same way, so apparently it's a thing). Clearly you know a bunch about the technical details for AC lighting and LEDs. Let me know if I can help you with the PoE control part.
View attachment 2558973

Not a whole lot of difference. So you have an AC input, DC output voltage source power supply which has its own idle power consumption and conversion losses. Then, you have a second layer of loss in the DC input, regulated current output LED ballast.

If the RJ45 output power supply is 90% efficient and DC input LED ballast is 85%, you're only getting 77% from plug to LED elements, not including copper losses in the RJ45. Both the power supply and the DC input LED ballast each have to have 95% or so efficiency to be on the same level of efficiency as better AC input LED apparatuses.
 

cvillej17

Member
Location
Pittsburgh
Occupation
Technical Advisor
Not a whole lot of difference. So you have an AC input, DC output voltage source power supply which has its own idle power consumption and conversion losses. Then, you have a second layer of loss in the DC input, regulated current output LED ballast.

If the RJ45 output power supply is 90% efficient and DC input LED ballast is 85%, you're only getting 77% from plug to LED elements, not including copper losses in the RJ45. Both the power supply and the DC input LED ballast each have to have 95% or so efficiency to be on the same level of efficiency as better AC input LED apparatuses.
Apples to Oranges, kind of. The IEEE code has losses built in that cover both power loss over distance and conversion losses at the node. Each network switch port can be up to 99w. Most switch manufacturers are advertising a 90w-per-port solution, but the real number the code sets is 71.3w at the end device.
I think the bigger argument is that PoE fixtures are class 2 low voltage (safe), have a much more robust power transformation, both at the network switch and at the node (the AC/DC transformer built into the AC LED fixture is the typical failure point), can be controlled, monitored, and diagnosed on an individual ballast level from a computer, and it can be used to transport other data on the same control network. A PoE lighting network eliminates the need for AC lighting infrastructure and it can be laid out and installed as part of the larger network infrastructure in a facility. With LEDs taking so little power, the AC infrastructure at 20A/circuit is no longer needed. It might be needed for other systems, but not for lighting.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Sooo, this whole thing isn't about PoE. Main point is that each fixture is addressable and powering over the same cable is just a convenience. No reason a line voltage circuit couldn't power them except for the extra work and the IT/LV guys trying to cut into the lighting business.

-Hal
 

cvillej17

Member
Location
Pittsburgh
Occupation
Technical Advisor
No, no reason at all. Clearly AC and AC powered fixtures are going to be around for a long time, and it might not make sense for a lot of people to use PoE lighting. But why, as a customer, would someone use heavy gauge copper, pipe, and boxes to power low voltage lighting when a network cable will do the same thing for less money? If controls are being pushed further into the code, then why not use a system that has controls and power on the same cable? Buildings that need to pull data can benefit significantly from the network a PoE lighting system already uses.

Most lighting systems are still fluorescent tubes. Even with incentives it'll take the rest of my working life to transition existing systems to LED. PoE shouldn't be a consideration for existing lighting systems. At best, PoE is a consideration for new construction and deep retrofit, but even then it isn't always a good fit. My stance is that it does make sense for some and that it's not just a fad.
Surely you have a better argument than, "this is the way we've always done it."
 
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