Things are about to heat up at Charter Steel. We're not talking smelters here, but network wiring closets.

Over the next few months, the company plans to roll out hundreds of IP phones to corporate desktops, with Power over Ethernet (PoE) switches to run electricity to the devices. The company recently upgraded its Avaya Definity phone switch to a network of Avaya S8700 IP PBXs , which are tied together over IP. This is where things could get hot, says Peter Schwei, telecom manager for the steel company.

As the company consolidated its data centre and voice technology, it installed new facilities that also provide the cooling needs for the new gear. But wiring closet environmental needs will have to be dealt with as the company switches from TDM-based handsets to IP phones.

Schwei says rolling out IP to desktops could pose the same problems facing local broadband providers. "It's the issues in the last mile, so to speak, that might get us," he says. The need to increase electrical feeds to wiring closets to support PoE, and the additional cooling systems required to keep gear from overheating, are now becoming more obvious as Charter Steel's VoIP deployment moves forward.

"Those are issues we will have to deal with at our distribution layer," Schwei says. "It's like cleaning out your sock drawer. You just have to do it."

In the heat of the night
Businesses installing widespread PoE gear for IP telephony or Wi-Fi access point deployments are finding the extra electricity that PoE gear can draw, and the additional heat the devices generate as a result, are factors that need to be taken into account.

It's a simple concept, experts say: Where there are electronics, there is electricity, which produces heat. Turn up the juice, and things get hotter.

With the deployment of PoE, the heat loads of telecom equipment migrates from a centralised telephone closet or electrical closet out to the distribution layer of the LAN.

"If you have thousands of phones and have multiple PoE switches, that can draw three to four times the power draw, and subsequent heat output," says Dave Story, enterprise power specialist for CDW, which sells IT products and provides consulting services.

In the past, Story says, most businesses installed critical air-conditioning systems for phone and server rooms, and that was about it. Now companies moving to VoIP and PoE technologies must consider cooling requirements for every space in a building where a LAN switch might reside - wiring closets and other nooks and crannies.

If stacks of PoE switches are replacing older LAN gear, not only is cooling a concern but increasing power feeds to wiring closets must also be factored in.

Often when you deploy core switches that provide PoE, new power supplies in the switch require new wiring.

"A lot of these boxes are not using a three-prong outlet," he says. This is more along the lines of electric dryer outlets.

Power management
Switches are getting better at managing how they distribute power, says Roen Heldman, vice president of product management for PowerDsine, a supplier of PoE components to LAN switch makers, such as Cisco and Foundry Networks. "It depends on the number of ports and the technique of power management that is used in the switch."

A typical switch is 70 to 100 watts, Heldman says. A switch with PoE can add 200 to 700 watts, depending on how it is implemented. Heldman says that if a PoE switch drives out 300 watts of power, and its efficiency is 75%, then: 300/75 = 120. That 120 watts equals 360 BTUs per hour of extra heat that has to dissipate in the communications room or wiring closet.

The IEEE 803.3af standard for PoE specifies 15.4 watts of power. But most switches aren't built to blast out that much electricity on all ports, Heldman says. PowerDsine and other PoE gear makers build power management features into their products that distribute only the power needed to endpoint devices. For example, most IP phones require from eight to 12 watts of power, Heldman says. Also, most typical PoE switch deployments do not have every port powering an end device.

In VoIP deployments, Heldman says, the extra heat dissipation of PoE switches must be added to the heat dissipation from additional UPSs.

Heldman says most UPSs are AC, which run hot because they convert their power streams from DC. But DC UPSs are something that should be looked at down the line, he says, especially if firms must dramatically increase the amount of UPSs installed to support VoIP-enabled switches in wiring closets.

"Today, most DC input is only used in the telecom and service provider markets," Heldman says. "My expectation is that in the future, more devices in communications and in data centres will go to DC," Heldman says. "But the practical issue is that most devices today use only AC. So even though theoretically DC may be the more effective way," it is less-widely used.

Whatever UPS technology is deployed in wiring closets, skimping on this gear could cause issues, CDW's Story says.

Power problems
Most desktop UPSs provide limited clean power, but can introduce delays during a switch-over when blackouts occur, which could disrupt latent-sensitive VoIP traffic. Higher-end power supplies that provide "double conversion" power conditioning - larger ones that are aimed at server backups - are more suited for wiring closet deployments where mission-critical VoIP PoE gear is running.

There are even more UPS considerations for sites that have their own generators, such as hospitals, schools and public safety facilities, Story says.

"There are UPSs that are generator friendly and ones that are not," he says. Most generators produced "dirty power," which means the voltage can fluctuate and is inconsistent.

"For mechanical equipment, such as elevators, this is OK. But for power-sensitive equipment, like electronics, this may cause problems. In extreme cases, such as with Ethernet switches, this could result in packet loss. On VoIP gear, this could also result in noise and interference on connections.