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IP telephony deployments struggle with power/heat issues

Mar 20, 20064 mins

Power-over-Ethernet switches, servers replacing key phone systems make data center hotter.

While the IP telephony market heats up, thermometers are literally spiking in some wiring closets and computer rooms where VoIP and power-over-Ethernet (PoE) gear is being installed, users say.

Equipment density and overheating are constant issues for data center managers; beating the heat is also becoming a top-mind concern for network and telecom staff deploying gear in wiring closets, as PoE and VoIP equipment are set up in places that once just housed lower-power switches, cooler hubs and patch panel racks.

“Power in general has been our Achilles heel in our [IP telephony] deployment,” says John Haltom, network director at Erlanger Health Systems, a southeast regional HMO in Chattanooga, Tenn.

Achilles heel might overstate it, as Erlanger has deployed over 1,500 IP phones in production, both wired and wireless, running off of a Nortel Communication Server 1000 IP PBX. To support IP telephony, Haltom and his staff installed PoE switches in wiring closets to light up the phones, and uninterruptible power supply (UPS) equipment to allow switches to run during a power outage.

These redundancy and power requirements challenged the healthcare organization’s IT staff, which supports one 112-year-old hospital.

“Trying to retrofit areas that are already cramped with larger PoE switches, larger UPSes,” was the challenge, Haltom says. “By the way, all that gear generates more BTUs, so you have to upgrade the AC units in those closets.”

By most measures, the biggest heat-boosters in wiring closets are the PoE switches, which do double duty in transporting Ethernet traffic, and acting as AC power supplies for all IP phones and other PoE-capable gear plugged into the devices powered ports. For example, Cisco’s non-PoE 24-port Catalyst 3750 LAN switch generates around 176 BTUs of heat per hour; add the PoE option, and the switch heats up to 534 BTUs. Add in a standard UPS that dissipates 80-100 BTUs, and you’ve more than tripled the heat output in just one wiring closet in order to support IP telephony. Similarly, Nortel’s 24-port Switch 420-T heats up to 220 BTU; its PoE-capable Switch 460-24T-PWR is more than double that.

Planning for how this gear will be cooled off and kept safe should not be an afterthought, experts say.

“All network devices should be placed in locations with … adequate heat dissipation, ventilation, and air conditioning,” according to Salvatore Collora and Ed Leonhardt, two Cisco Certified Internetwork Experts, writing in Planning the Cisco CallManager Implementation, published in 2004 by Cisco Press. “Although it is surprising, some deployments actually store servers and switches in broom closets and under desks. Improper care of your equipment contributes to environmental and security hazards that can disable or degrade your voice deployment.”

This could especially be true in small businesses, where an older key telephone system is being replaced. These devices combined call processor, phone power supply and switching and could be stored almost anywhere. However, companies should have a cool, dry place ready for newer IP PBX gear.

“In certain climates, you could have very high humidity, with the ambient temperature getting above [104 degrees Fahrenheit],” says Patrick Ferriter, vice president of marketing for Zultys, a maker of IP PBXs that targets the small-offices as a key system replacement.

“There are places where it does get hot, and you’re going to have problems if you don’t have air conditioning.” How much cooling will depend on the IP PBX itself, he adds.

“If you have an IP PBX which has built-in gateways, and if you have a lot of analog connections — FXS boards which provide ring voltage — it could start to get even hotter,” Ferriter says. “It’s going to be hotter than a traditional key system for sure.”

VoIP environmental fundamentals When putting an IP PBX or Power over Ethernet (PoE) LAN switch in a wiring closet to support IP phones on desktops, consider power and cooling requirements for the equipment, experts say.
A sampling of environmental/power specifications of some IP PBX/PoE LAN gear:
IP PBX gear
VendorProductHeat (BTUs per hour)Operating temperature
3ComNBX 10092332 to 104
AvayaS8700 Media Server1,00040 to 110
CiscoMCS 782585350 to 95
NortelCS 10001,02450 to 95
Service provider
3ComSuperStack 3 Switch 440093832 to 104
CiscoCatalyst 3750 G-24PS53432 to 113
ExtremeSummit 400-24p54632 to 104
NortelSwitch 460-24T-PWR57532 to 104