Planning for Power

Technology is reshaping-and redefining-today's educational facilities. Whether integrating a completely new system or upgrading existing technology, careful consideration must be given to electrical-power design.

The introduction of computers and other technology devices into an existing building exacerbate the common electrical-power issues familiar to most engineers and facility planners. For example, computers are extremely sensitive to input power fluctuations and must not be mixed with other loads. This occurs because computers induce harmonics into copper wire, creating extra heat in the neutral conductors, often requiring larger or special transformers. Computers also require an excellent grounding system with a single, common grounding point. Printers and other equipment require dedicated branch circuits so as to not corrupt data transmission. Other educational technology components, such as wireless control systems, require advance planning so that RF and infrared systems do not produce interference, or retard operation of existing systems.

Establishing objectives Among the planning considerations required when designing major technology upgrades for older buildings include power distribution, branch circuits, lighting, resistive loads, segregation of power, mitigating interference and pathway design.

The first objective must be to field verify existing electrical conditions with regard to code compliance, fire/shock safety, available power and spare capacity. Generally, old buildings have inadequate, or even dangerous, wiring systems with several modifications made incrementally over a period of many years.

The second objective must be to evaluate the existing electrical work and design the new systems that will be needed for the technology upgrade. The design must include:

-New electrical work for the technology power system.

-New code-compliance work for renovating the existing power system. All new and renovation work must meet the NEC Code, applicable local codes and EIA/TIA standards for the technology system.

When evaluating the existing conditions for the project, follow these recommended steps:

-Obtain the salient electrical-service information from the serving utility company. This data should include service and metering locations, transformer KVA size, voltage, phase, maximum KW demand, service phase conductors and neutral sizes.

-Develop a power one-line diagram to identify and size the existing main service equipment, main secondary feeders and conduits, transformers, power panels and lighting panels.

-Attain nameplate data for the main switchboard, transformers, power panels and lighting panels.

-Make a schedule for the main service equipment to show location, size and type of overcurrent devices.

-Identify all loads served from the main service equipment, such as air-conditioning motors and elevators.

-Make panel schedules for each power and lighting panel to show the following nameplate data: manufacturer, type, size of main lugs or main overcurrent device, type and size of active branch circuits (fuses or breakers), and the size of any spare branch circuits. Also, show the size and type of branch circuit wiring to ensure the fuses or breakers are not oversized for the wiring.

-Check existing service grounding for conformance to NEC.

-Check the existing equipment-grounding system. Determine if the equipment grounding depends on an unreliable metallic conduit system, which may have loose couplings, or be corroded under slab conduits. In addition, determine if the equipment grounding has reliable green copper conductors running from the main service equipment to the panels, as well as branch circuit conduits from the panels to the loads.

-During a time of high demand in the facility, check and document the actual current draw of each feeder phase conductor and neutral conductor to ensure the feeders are not overloaded. Also, make sure the current does not exceed the rating of each panel. Note any spare capacity.

-Check all panels for overheating of the entire panel or of individual branch overcurrent devices.

Before proceeding with the design for the new technology system, and for the safety of life and property, make notes of any existing code, fire or shock safety violations, and communicate safety recommendations.

The state of existing conditions and the extent of the proposed new loads will determine the new power modifications. An inadequate power supply, power distribution or special provisions needed for a major technology upgrade may require a major electrical upgrade.

Technology power design After evaluating the current electrical conditions in the building, the following design considerations for the project can be put in place:

-Ensure conformity with the latest EIA/TIA standards in the design for telecommunications closets (TCs), raceways, circuits and grounding.

-Be certain to coordinate new loads with the serving utility to ensure the service transformer is rated properly for the extra heat effects from current harmonics.

-Note that the secondary service conductors may need to be replaced because of the additional load.

-The secondary service neutral should be doubled in size because of the harmonic effect.

-Keep electronics equipment away from inductive loads, such as transformers and motors.

-Keep all computer loads on dedicated panels that do not serve other loads (e.g., motors).

-Put a maximum of six computers per 20 ampere circuit with a separate neutral for each circuit. Do not use "combined" circuits without doubling the common neutral.

-Do not connect printers to computer circuits. Use dedicated circuits for printers.

-Provide separate dedicated circuits for fax machines and other equipment associated with technology.

-Provide a transient voltage suppressor for each computer panel and the main service equipment.

-Consider special switching for room lighting in computer areas to enable control of the lights during projection of computer images or other multimedia applications. Also consider a monitor switch at the primary instructional wall to allow a teacher to turn the monitors on and off.

-Provide appliance receptacles in computer areas. These receptacles should not be connected to the computer circuits to avoid computer crashes when a vacuum cleaner or similar equipment is connected.

-Provide 20 ampere dedicated circuits for coffeemakers, microwaves, refrigerators and other appliances.

-Coordinate special requirements for reliable power sources, such as UPS units to all mission critical devices (e.g., file servers, data hubs or switches).

-Consider color codes or engraved nameplates for receptacles to identify usage in an effort to minimize power interruptions to the computers.

-If existing wiring is planned to be used for a few circuits, either replace the wires, or field-verify wiring conditions. Also, verify the size of fuses or circuitbreakers. Generally, old facilities may have oversized fuses or "frozen" circuitbreakers that will not operate when overloaded. Replace existing work as required for safety.

-If there is any question with regard to the electric service or safety of the interior wiring, the local power company and the approving electrical authority can be very helpful for general inspections and recommendations.

Thoroughly planning for the implications that technology infusion creates on the electrical service can help a school maximize its investment by ensuring a stable and conducive electrical infrastructure. This will reduce problems in operation, extend the life of the electronics involved, and provide for future expansion.

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