A single ethernet cable can carry both data and low voltage electrical power, which helps to reduce the cost of installing separate power and data wiring. Manufacturers are now designing electrical devices such as access card readers and low voltage lighting to work with ethernet cables.
Technology
Single cable carries both data and power
Ethernet cables have become a common standard for wired internet connections, but they also have the capacity to carry low voltage electrical power—and to cut the cost of wirng wiring installations substantially.
“I see Power Over Ethernet (PoE) as one of the most undervalued technologies in electrical installations today,” says James Sinopoli, author of Smart Building, and Managing Principal of Sinopoli and Associates of Spicewood, Texas.
Sinopoli recalls in the early 1980s, the specifications for data cables varied from company to company.
“Every vendor from IBM to Wang had their own distinct cable designs. By the early 90s we were seeing Ethernet Cable becoming an international standard.
“What spawned the use of PoE was what happened about six or seven years ago,” says Sinopoli.
“Traditional telephones have their own power source supplied over phone cables. When companies began to move to Voice Over Internet Protocol (VoIP) telephones, they were left with phones that suddenly required both a telecommunications cable and a power outlet.
“Rather than installing a new electrical outlet for each telephone, the industry created a standard to run low voltage power through the ethernet cables.”
The use of PoE soon spread to wireless access routers, then slowly to other devices that could run on low voltage.
“The big advantage is that any devices you power using ethernet cables can be managed through the cables as well,” says Sinopoli.
“In the traditional operation of a building, you might install a security camera system by running a cable to the camera location, then running a separate 120-volt power supply to the camera including conduits, wires and back boxes. With PoE, you only need to run one cable, saving labour and material costs. “
When Indiana’s Purdue University committed to serve the entire campus with more than 1,100 wireless access points, it opted to power them solely using ethernet cables. The university estimated that it saved between US$350 and US$1,000 per access point by choosing PoE.
Other studies estimate it costs about US$864 to provide power to a device using traditional wiring, and about US$47 to US$175 for PoE, says Sinopoli.
Manufacturers are now taking advantage of PoE by designing electrical devices to work specifically with ethernet cables. These currently include access card readers, clocks, paging system speakers, intercoms and low voltage lighting.
The advantages of the technology include:
* Lower product manufacturing costs. Since ethernet cable is standardized across the globe, manufacturers no longer need to supply different power cords.
* Energy savings. Low voltage devices consume less power. Users can also monitor the consumption power of attached devices, or shut them off remotely, via computer.
* Increased safety. The use of lower voltage cables reduces fire and shock hazards.
A new standard, PoE Plus, is now being developed to provide increased wattage to devices, such as tilt and pan security cameras, requiring a little extra power. The new standard will essentially double power output from 19 watts to about 35 watts.
While PoE is catching on in Asia and some European countries, North America has been slow to warm up to the technology.
“The design process is not keeping up with technology,” says Sinopoli. “Building owners and managers simply aren’t aware that they can use ethernet cables to supply power. When they’re introduced to the budget implications of switching to PoE, they like what they see.”
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