In Columbus, Ohio, a six-story law-school building requires cooling year-round.
“A lot of buildings we can cool with outside air,” Mike Klingler, service manager for HVACR contractor Farber Corp., said. “When we get down to 50 to 52°F and below, we can just draw that outside air in and use it for free cooling. But because of the setup of the law-school building, they had to run one of the chillers even when it was 20 to 25°F outside. Because of the duct distribution system, we couldn't rely on outside air in certain areas of the building.”
One of the facility's two 200-ton-capacity chillers was kept running to supply 45°F water to air-handling units to keep the building's occupied spaces comfortable.
The building uses hot-water heating and chilled-water cooling, with a dual-duct system for air distribution. Hot and cold air travel to terminal units, which mix flows to the required supply temperature. Water chilled to 45°F is pumped to the air handler, where it cools supply air. In the process, excess building heat is transferred to the water, warming it to about 55°F. That warmer water then returns to the chiller, where it is cooled back down to 45°F and pumped back through the loop.
With plenty of cold air available outside during winter, Klingler figured he could bypass the chiller entirely. His plan was to use the cooling towers on the roof to cool condenser-side water to 45°F and pump it through a plate-and-frame heat exchanger to extract waste heat from the chilled-water loop. Instead of the chiller's powerful compressor motors, the system would run with just a small pump. The cost of the upgrade would be significant, but Klingler felt he could justify it with accurate data on the potential energy savings.
Using the Fluke 975 AirMeter test tool, Klingler could measure multiple indoor-air-quality factors before the upgrade, then check afterward to ensure air quality was not compromised. Using a beta test version of the new Fluke 1735 Power Logger, he logged actual kilowatt-hour consumption at the chiller over multiple 12-hr cycles.
“You can set this tool up and walk away, then come back and get the information,” Klingler said. “You can see what your real power consumption is for any equipment in your building and then equate that to real dollars.”
Proving the Payback
Klingler's measurements with the Fluke 1735 showed the chiller consumed an average of 790 kwh of power over a 12-hr period. He determined total power consumption over the four cold-weather months was 189,600 kwh. At a cost of 6 cents per kilowatt-hour, running the chiller was costing the school $11,376 every winter. Klingler figured his alternate approach would cut that bill by 87.5 percent, for an annual energy savings of $9,954.
Klingler estimated that installing the heat exchanger, piping, valves, and controls would cost $46,000. That meant the payback period for the project would be just 4.62 years.
Beyond measuring power consumption, the Power Logger collects all kinds of power-quality information, while the AirMeter makes calculating percentage of outside air required to meet standards easy.
Working on a one-floor remodel in a 10-story office building, Klingler had to calculate the percentage of outside air to be delivered to a newly laid-out conference room.
“With the 975 AirMeter, the service company can go right into the air handler and take those readings, and it will tell us, based on temperature or carbon dioxide,” Klingler said. “It's a very quick, easy, labor-saving tool.”
On the power-quality side, the Power Logger measures voltage on three phases and current on three phases and neutral. It records multiple parameters that can help determine system load, including voltage, current, frequency, real power, apparent power, reactive power, power factor, and energy. And it downloads to a personal computer and comes with software for creating reports.
Information and photograph courtesy of Fluke Corp.