At Allina Medical Clinic in Forest Lake, Minn., temperatures in the 10-ft-by-12-ft data room, which houses network switches and other computer and telecommunications equipment the clinic depends on for day-to-day operation, were high, but acceptable. That changed with the installation of additional switchgear and computer equipment and a larger uninterruptible power supply.
"The heat load in that space had been marginal before, but now it was out of control," Maintenance Manager Matt Steding said. "It became clear that the room needed its own dedicated cooling system."
In weighing his options, Steding ruled out a split system as too labor-intensive to install and maintain.
"Ambient temperatures in our region range from −10°F to +95°F," Steding said. Such extremes put an extra load on an external compressor and condenser, resulting in increased maintenance costs.
From the standalone solutions he considered, Steding selected a MovinCool CM25 ceiling-mounted air conditioner, which he purchased from Spot Coolers, a national supplier of air conditioners.
The CM25 is an air-cooled unit with a cooling capacity of 25,000 Btuh, a sensible-cooling capacity of 18,900 Btuh, and a seasonal energy-efficiency ratio of 14, which are made possible by its energy-saving variable-speed inverter compressor and inverter fan motors. The unit measures 20 in. high, which allows it to fit easily in the ceiling space typically found above data rooms. Its built-in mounting bracket, vibration isolators, and flanges allow installation using standard off-the-shelf hardware.
"The MovinCool CM25 ... was economical from the standpoint of both purchase price and ease of installation," Steding said. "Also, it's a complete, self-contained unit, so, unlike a split system, there were no refrigerant lines to run and no outside compressor and condenser coil to install and maintain."
Installation consisted of attaching the CM25 to the ceiling, connecting the intake and exhaust ducts, running a drain line from the unit's built-in condensate pump to the P-trap of a sink in an adjacent maintenance closet, and wiring the unit to a 230-v electrical circuit.
Normally, the final installation step would have been to attach the CM25's wall-mounted controller thermostat, which provides comprehensive communications, monitoring, and self-diagnosis capabilities. Steding, however, wanted to control the CM25 with the company's Alerton energy-management system (EMS) at the company's headquarters. Thus, he had Allina's in-house HVAC technicians install an Alerton visual logic controller, which they wired to the CM25's control board. Simply switching a dual-inline-package switch on the board allowed them to interface the EMS with the CM25 and take over control of the unit.
"The flexibility of the CM25's control options made it very easy for us to integrate the unit into our automation system, which gives us remote monitoring and enhanced control capabilities," Steding said. "The EMS lets us build the control logic that fits our needs. It allows us to monitor, schedule, trend, and alarm the points we want, so we have greater control over the unit."
Steding said he plans to install CM25s in other Allina clinics.
Information and photograph courtesy of MovinCool.
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"Data-Center Uptime & Energy Efficiency" by Don Beaty, PE, FASHRAE, in the October 2010 issue of HPAC Engineering discusses the difficult—but not impossible—balancing act managers of mission-critical facilities face when looking to reduce energy use.