Chiller Maintenance for Savings, Profits
May 10, 2010
Chiller maintenance is becoming more vital than ever before. Better maintenance can mean valuable energy savings and better bottom-line profits.
That was the thrust of a presentation titled “Raising the Bar on Chiller Maintenance” given by Kip Bagley, vice president of service for Mesa Energy Systems, and Rod Kraft, branch manager of EMCOR Services Arizona, at a webinar event jointly presented by The NEWS and Goodway Technologies Corp.
In his part of the presentation, Bagley described chillers as “usually the single largest energy user in the building” with “large installation cost. A chiller must be maintained and serviced properly by a knowledgeable and technical-savvy staff.”
He cautioned, “Lack of maintenance equals major failures, which equals large dollars and costly downtime.”
MECHANICAL EFFICIENCYMechanical efficiency in a building can encompass chillers, cooling towers, and overall system operations, Bagley said.
“Chiller efficiency involves cooler and condenser approach temperatures, refrigerant contamination losses, cooler and condenser water flow, and chiller control systems.
“Cooling tower efficiency involves fill media cleanliness, approach temperatures, water flow, mechanical condition, the cooling tower control system, and the water treatment system.
“System efficiency involves optimum start and stop times, the interface with air or waterside economizers, pump control, and cooling coil control.”
He said a typical energy calculation involves:
Run Hours x Tonnage x Efficiency x Cost in kW = Cost per Year
“Run hours are expressed as full-load equivalent hours. In our part of the world, this is usually between 2,200 and 2,500 hours per year.”
Taking what he said is typical California rates, he gave an example:
2,000 hours x 500 tons x 0.7kW per ton x 13 cents/kW = $91,000 annual energy cost
“So a 500-ton chiller has an annual cost of operation of $91,000. If there is a 10 percent energy loss, that adds a $9,100 loss to the bottom line. Can your customer afford that?”
He then ticked off ways to perform better chiller maintenance:
• Annual cooler and condenser tube brushing;
• Annual refrigerant contamination testing;
• Annual check of design water flows; and
• Annual chiller control calibration and testing.
In-season inspections, consisting of adding one or more in-season cooling load on the chiller to log chiller under loaded conditions and perform the refrigerant contamination test then.
PREVENTIVE MAINTENANCEIn detailing aspects of the chiller, Bagley touched on preventive maintenance considerations. For heat transfer surfaces he recommended that technicians “use a qualified water treatment specialist, clean condenser tubes as needed, clean water-side strainers, and test tubes every three years.”
When it comes to tube fouling, he said waterside contamination comes from scaling, slime, biological growth, and corrosion products. Refrigerant-side contamination comes from oil entrainment and air in the system.
Another aspect of chiller technology discussed during the webinar was the purge system. “Low-pressure chillers typically include a purge system to remove air and moisture that may leak in, while minimizing the emission of refrigerant. The purge consists of a small refrigeration system, a pump-out system, controls, and a filter drier.”
TUNEUP/RECOMMISSIONINGBeyond preventive maintenance, Bagley said there were other approaches to better efficiencies especially related to building tuneups and recommissioning of a building.
“Compare all mechanical systems to original design and current conditions,” he said. “Identify building needs changes from original design requirements. Re-engineer necessary changes.”
He also stressed the need to consult with the original engineer if possible and use contractors specializing in such work.
CLEANING PRODUCTSKraft used his portion of the webinar to discuss some of the cleaning products for chiller maintenance. He said chiller tube cleaners allow for smooth and enhanced tubes. Quick-connect fittings allow “for quicker brush change to save time.” He encouraged those involved in such work to make sure the brushes are the kind “that cannot twist off the shaft and require no tools for changing.”
He added that there are tube cleaning units available with reversible shaft rotation, another advantage. Among other components in a tube cleaner are shaft feeder guns, and chemical injection with power flush.
For more information, visit www.goodway.com.
The NEWS/Goodway webinar was one of a number put on annually by The NEWS. For information or to register for upcoming webinars, go to webinars.achrnews.com.
Publication date: 05/10/2010