Rental-equipment options cover the spectrum, from portable coolers to trailer-mounted units that replace the entire primary cooling system during a renovation project or act as supplemental or standby emergency cooling. Renting is an excellent way for managers to check if a particular unit is sized properly and includes the right accessories before committing to a purchase.
The planning process begins by answering the question, "What is the cooling objective?" The next step is to determine the cooling load and alternatives for cooling. Managers want to get a unit that will do a satisfactory job of cooling efficiently. This requires careful, accurate calculation of the cooling load, and the proper selection of efficient cooling equipment.
Once a manager has determined the proper size for the unit, they can move on to other specifications, including:
In addition to these specifications, managers also should compare the seasonal energy efficiency rating (SEER) for each equipment option. SEER is the ratio of the Btu output to the watt-hours input, or Btu/watt-hour. The higher the rating, the lower the cost.
With this rating, energy use and electricity rate, managers can estimate the unit's annual energy cost. To do this, divide the cooling-unit capacity in Btu by the SEER. Multiply that total by the cooling-load duration in thousands of hours per year, and multiply that result by the electricity cost in dollars per kilowatt-hour.
For example, if the Btu capacity of a server cooler is 36,000 and its SEER is 10, and if the cooling load in thousands of hours per year is 8 and the electric cost is $0.08, the annual cost is 36,000 divided by 10, multiplied by 6, multiplied by $.08, or $2,304. If the SEER is 12, annual cost is $1,920, which means a savings of $384 per year by selecting the more energy-efficient unit.
The best planning will not be good enough if the equipment does not arrive in a timely manner with all necessary accessories. In weighing rental options, managers need to ask about time-sensitive delivery guarantees to ensure the unit will arrive when the facility needs it the most.
Thomas A. Westerkamp is a maintenance and engineering management consultant and president of the work management division of Westerkamp Group LLC.
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