BICSI's 10th edition Telecommunications Distribution Methods Manual, (TDMM) deals with many aspects of power distribution.
July 1, 2005
The practice of providing an uninterruptible power supply (UPS) has been around for a long time. Recently, however, UPS has become the term referring to a number of different facets of power supply for an information transport systems (ITS) network.
As we see more emphasis on power in the ITS network we should understand that the definition of UPS does not cover all the components of power in an ITS network. (Maybe we should redefine UPS to be universal power systems)
The ITS designer (and as always I recommend using a BICSI Registered Communications Distribution Designer) has two major issues when dealing with power: the traditional UPS used in providing backup power and power conditioning, and the newer issue of powering devices over the cabling system such as power over Ethernet (PoE) or other methods.
UPS issues center on being able to provide power to support device loads (wattage and volt-ampere [VA] ratings) and a length of time for those devices to run. Sizes can range from a unit to provide a personal computer time to shut down “gracefully” to a major generator providing an entire building with multiple days worth of backup power ability.
Conditioning refers to the ability for a UPS to provide clean power with no sags, spikes or over-voltage, thus preventing damage to the devices being protected.
Since there are so many ways that manufacturers provide run times vs. loads and different methods of providing conditioning, I suggest reviewing manufacturers’ Web sites and consulting with your local sales engineers to get the information you need to design a UPS/power conditioning system for your clients.
Powering devices over cable has become a popular way to save on costs of running separate electrical service to each device. It also provides a way to control power to the device (PoE only provides power when needed), and can centralize UPS requirements for multiple devices, as the power supplies are centralized in a rack or cabinet.
Currently, PoE is able to provide low wattage power at 12/24/48 volts DC and is only present on the cable when required.
That is because of “handshaking” protocol to turn on power only when the appropriate device is connected. Therefore no device means no power on the cabling. And advances in technology and increased wattage availability may mean we’ll be able to power our PCs over our cabling infrastructure. Think of the savings that will bring.
Since cabling design typically occurred early in the overall ITS design, it was not usually necessary to consider issues of powering telephone sets and peripheral devices such as cameras and security devices.
Before moving ahead with a final design, there are many issues these days the RCDD has to consider related to power: These include what devices are being supported, are they powered and, if so, how (PoE or another power method), do the devices need mid-span or end-span, will they need backup or uninterrupted power, and what is the individual and overall power load needed?
As for the designer, issues he or she should consider include where is the power supply located, is there enough space, will there be a need for racks or cabinets, will grounding and bonding be sufficient and will additional power supplies affect cooling loads in the cabinet room or data centre?
If there is cooling, are fans required and will the fan noise be disruptive for people in the immediate area?
Working with manufacturers who provide devices, power supplies, racks/cabinets, cooling units and UPS units is critical to ensuring your design will function optimally. As well, if you do not have the necessary electrical skills you will want to partner with an electrician or electrical engineer to ensure you meet all codes and safety requirements.
Now more than ever, it seems that designers must rely on interpersonal communications to be sure we meet the needs of a customer.
BICSI’s 10th edition Telecommunications Distribution Methods Manual, (TDMM) deals with many aspects of power distribution affecting the design of ITS, including power problems, power conditioning and power protections.
Roman Dabrowski, RCDD, is the Canadian Director of BICSI and a Director of Product Management with Bell Canada. He can be reached via e-mail at email@example.com.