Discover Copper Online

Spring 1995

Copper Helps Protect Precious PCs

Recyclable Copper: This colorful wire painting was created out of salvaged telephone wire by New York artist Len Rosenfeld. Such wire art pieces take from one to two months each to create.
It's taken a lot more copper plus a much bigger uninterruptible power supply (UPS) for Wisconsin Public Power, Inc., (WPPI) to protect its precious PCs.

When WPPI occupied its new $2 million building four years ago, only 6 of its 40 vital PCs were tied to a UPS. Soon, it became apparent that this was insufficient backup. In addition, the following problems were reported by Beverly Lindquist, Director, Member and Computer Services, "We experienced memory errors, data was lost and vital PC boards and power supplies acted erratically. In addition, momentary outages and voltage sags played havoc with the networked PCs."

WPPI is a nonprofit municipal electric company owned by 30 cities and towns scattered all over the dairy state. Located in Sun Prairie, WPPI controls and dispatches power to its member owners. Some of the power is generated on WPPI's generators, but a significant amount is purchased from other utilities.

The agency's PCs - there are now 50 386s and 486s, primarily from Compaq and IBM - must operate without fail around the clock. To rectify the building's power problems, WPPI hired Arnold & O'Sheridan, consulting engineers based in nearby Madison, the state capital. They began their analysis in January, 1994.

Retrofitting began with installation of a much larger UPS - a 50KVA model from Liebert Corporation, Columbus, Ohio. It supports all the PCs plus telephones and security system. Copper cables from the UPS in the mechanical room in the street-level garage were run to new panel boards at each level 1 . Power to the PCs from the panel boards is now distributed to power outlets on each floor painted orange.

To accommodate the harmonic voltages, neutral wires in the three-phase power network were doubled in size and circuit-breaker capacity was upgraded. In addition, provision has been made to tie into a back-up portable power generator to be purchased in the future. Retrofitting was accomplished by a local contractor, Schultz Electric, Inc.

The total cost including consulting services was $100,000. Has it been worth it? "We've had no problems since the retrofit," said Lindquist. "In fact, when all power to the corporate park in which we are located was cut recently for two hours to accommodate new construction, our PCs were supported without a glitch by the UPS. And, thanks to the upsized neutrals, we are no longer plagued with destructive power quality problems."

If only 50 PCs require so much care, it's easy to understand how the problems multiply with much larger numbers. Consultant Marty Martin, who managed the WPPI project for Arnold & O'Sheridan, had to cope with thousands of PCs at the headquarters of Cuna Mutual Insurance Society, also of Madison. The facility consists of three interconnected, four-story buildings totaling one million square feet housing about 4,000 employees.

To cope with the intense harmonics generated by PCs, Martin recommended the following:

  • Doubling the size of neutrals
  • Replacement of on-site transformers, needed to lower the entrance voltage from 480 to 120, with K-rated versions that can handle high-frequency harmonics without overheating
  • Limiting the number of PCs on any one circuit, which required more circuits plus breakers
  • Moving laser printers to circuits without PCs
"K-rated transformers cost about 15% more than conventional transformers of the same capacity, but the added investment is justified if present transformers overheat," said Martin.

Henry Straw, Cuna's chief electrician, told of the care needed in circuitry because the modular office units have built-in cabling. He also reported that only a small minority of the thousands of PCs on site are supported by back-up power. The UPSs are small units from Best Power Technology, Inc., of Neenah, Wisconsin.

Arnold & O'Sheridan: 608/271-9651
Best Power Technology, Inc.: 800/356-5737
Liebert: 614/438-6900

1. Editor's Note: Copper cables can carry more power for their size than aluminum - an important safety, space and future expansion consideration.

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