According to the Copper Development Association, certain guidelines should be followed in upgrading electrical wiring for the digital office. Since nowadays there is a computer on practically every desktop, these recommendations could apply to almost all offices; however, they are especially important in critical areas for which downtime is not an option.

An upgraded electrical wiring system incorporates nine key design elements:

 

1. Independent computer and utility circuits.
2. Fewer cubicles and fewer outlets per branch circuit.
3. Separate utility and computer step-down transformers.
4. K-rated transformers specified for computers.
5. Printers and other peripherals on branch circuits separate from computers.
6. Large gage (#10 AWG) copper wiring for branch circuits.
7. Separate neutrals for each phase and double-sized feeder neutrals.
8. Surge protection in three stages: at the service entrance, at the distribution panels and at the outlets.
9. Often, isolated ground wires for computer grade circuits.

The goal is to make the office space suitable for computer intensive office environments for many decades to come. The above design elements can be adopted within the constraints of a modest budget. These recommendations would be considered well above average, or even excellent, for most office buildings in the United States today.

“Many offices cannot accommodate the special electrical requirements of the digital work environment, because they were built when office workers were still pounding away at typewriters,” said David Brender. “Workers in these offices are plagued by frequent computer crashes, and significant productivity losses occur during the downtime.”

According to Brender, one of the most important actions that can be taken in upgrading a wiring system is to isolate the desktop computers from the heavy machinery, lamp ballasts, blowers, air conditioners, microwave ovens and coffee machines. “The idea of an all-purpose electrical circuit is out of date,” he explains. “Electricity should be distributed throughout the building in two distinct subsystems: the computer system, and the utility system.”

The branch circuits to computer outlets are sometimes termed “C branches” or “C circuits”; the branch circuits to lighting and utility outlets are sometimes termed “L branches” or “L circuits.” Following this approach, every workstation may have two sets of electrical outlets: one for computers and peripherals and another outlet for general uses.

 

Any computer circuit should be electrically separate with respect to any utility circuit - all the way back to the service. Thus, each C circuit is fed from its own panel, which in turn is fed by a separate feeder and supplied by a separate transformer. (The Institute of Electrical and Electronics Engineers [IEEE], New York City, even recommends separate conduits or troughs for separate circuits.) For an electrical disturbance to pass from the utility circuit to the computer circuit, it would have to pass through two transformers and many feet of wiring. Most transients occurring in the utility circuits are thus effectively diminished by the two transformers and have minimal, if any effect on the C circuits.

Some wings of office buildings may contain more than 100 cubicles. Fewer outlets per branch circuit and fatter wires mean the load carrying capacity of the copper wiring may be well above the actual electrical usage. Yet, power quality is greatly improved, and the building is ready as electrical demand in the office environment grows.

“The reasons for computer crashes almost always lie with a building's wiring and grounding, which are outside the zone of responsibility of the utility,” said Brender. “Older facilities that have not yet been upgraded commonly are plagued with unexplained computer crashes or diminished equipment life.”

For more information on high tech wiring solutions, contact the Copper Development Association Inc. (CDA), New York City, at (212) 251 7200. Or visit the CDA website at: www.copper.org/PQ. David Brender is National Program Manager for the Copper Development Association (CDA) in New York City.