Dr. Gerald Zetter Center, Edmonton, AB
A new air cooled chiller was required to replace the existing 320 ton unit that used an ozone depleting refrigerant.
The budget for the project was $420,000 and included the replacement of the chiller, new structural frame rail supports, and tie-ins to the existing (obsolete) building management system. During the schematic design phase of the project, Clark Engineering was able to show that the actual building requirement for cooling, based on historical utility data and maintenance records, was significantly less than than the capacity of the original chiller. Clark Engineering selected a 250 ton high efficiency magnetic bearing chiller with a footprint that could be accommodated with minor modifications to the existing structural supports. Because of the reduced cost of the chiller and associated structural savings, it was possible to provide new variable speed drives for the existing chilled water pumps and air handling unit fan motors. A significant part of the building management system was also replaced within the budget. This system has completed its first two summers of operation and despite the significant reduction in size, has proven to have an estimated 20% excess capacity. Although the commission for design of the system was not awarded until mid December, 2010, the new chiller was started up in June 2011. Temporary cooling for the month of May was provided using domestic water, allowing the building to remain fully operational during the construction.
We have found that in existing buildings, historical utility and operations information often reveals overly robust system sizing. In retrofit and upgrade projects, existing mechanical systems sizing should be reviewed from a Lean Design viewpoint to ensure that sizing is appropriate. Regardless of what systems are adopted, ensuring that capacities are appropriate will lead to a reduction in material and equipment required, resulting in capital and energy savings, lower maintenance costs, longer life, and a reduced environmental footprint.