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The pros and cons of Power over Ethernet lighting

Whether they are homeowners looking to stretch their budget or facility managers working toward green building certification, your customers want to reduce their energy consumption. WithPower over Ethernet (PoE) lighting, their energy savings can be delivered via theirstructured wiring system.

PoE technology allows direct current (DC) electrical power and data to be carried together on a Cat 5 (or higher) twisted pair cable. PoE was first used for Voice over Internet Protocol (VoIP) systems. In 2000, Cisco introduced a proprietary technology that allowed Ethernet cables to transmit 48 volts of DC supply to VoIP phones. Other companies followed, and soon PoE was commonly used in office VoIP systems.

In 2003, the Institute of Electrical and Electronics Engineers (IEEE) released a standard for PoE. This was updated in 2009 with a standard that could carry more power. The result was that a single RJ45 connector and Cat 5 cable were capable of transmitting 30 watts of power.

Ultra PoE is a non-standardized version that supplies up to 60 watts of power, and soon a 100-watt PoE version will be available. As the available power increases, PoE lighting will become attractive to a greater number of your customers.

PoE lighting systems use Light Emitting Diodes (LEDs), which are the most energy-efficient lights on the market to date, using 75% less energy and lasting 25 times longer than incandescent lighting.

With PoE lighting, the lights connect to the IT system in your customer’s building. When combined with sensors and small processors that can make decisions about lighting, these systems can provide additional energy savings. A PoE lighting system can, for example, be configured to light only areas with inhabitants.

PoE design and installation

The power budget is a critical feature of PoE lighting since each cable can carry only 60 watts of power. For delivery to a large building, zone cabling can be a good option. In a zoned cable system, consolidation points act as hubs from which the cable delivers lighting, internet, and other IoT services.

Another design consideration is whether to use a centralized or distributed approach. A centralized system in which all PoE switches are located in acentral hub is the more common approach, but it requires a lot of cabling, and the cables are limited to a length of 100 meters.

A distributed system uses smaller switches set up in each zone. This requires less cable and removes the cable length limitations, but maintenance and repairs are challenging. In a distributed system, switches will need to be maintained throughout the building instead of in one central control room.

Power issues

Your customers who switch to PoE lighting can save up to 33% in energy costs, and proponents of PoE argue that the power supply is more reliable. But it’s not that simple. For one thing, category cables have a lot of voltage drop unless six of eight conductors carry power and only two carry data. As well, there is significant power loss over distance with DC power.

When standard lighting has a power outage, the lights return immediately when power is restored. With PoE lighting, a system reboot may be required to get the lights back on so; network integrity is of paramount importance. Your customers might be able to survive without internet for a few hours or days, but functioning without lights is more difficult. One way around this is to install a battery backup for the switches.

Another issue is interference. There are no problems running DC on a shared line with data, but the lighting circuitry could create electrical noise that interferes with your customer’s internet service.

Your customers need to be aware, also, that any change in their lighting will require extra care. They won’t be able to replace a fixture with any option they happen to like. They will need equipment that is compatible with their system.