Installation: Getting It Right
The most critical part of any chilled-water system is its installation. Here's help in meeting the challenge of especially difficult small systems. Chiller applications, especially smaller ones, can be a challenge. Systems sized at 10 tons or less usually are handled at the maintenance facility level without the benefit of on-site technical representation. Seventy percent of chiller system issues brought to Tecumseh's technical department relate to the most critical part of any chilled-water refrigeration system: the installation.
During chiller installation, there are a number of variables to consider, any one of which could have a major impact on efficiency and operability. Some are so simple they often are overlooked, for example, location. Check to see if there is a heat source such as other machinery near the targeted installation area, which can increase ambient temperature and the chiller's efficiency. Also, ventilation exhaust and process vents can contribute to higher ambient temperature.
Simply positioning your chiller for convenience may mean the potential for airflow problems has been overlooked. Insufficient airflow is a common problem, often because the chiller is too close to a wall or adjoining equipment. Both situations can impede airflow. Chiller manufacturers can provide the minimum clearance requirements for a chiller to maximize airflow and system efficiency.
Long piping runs and improper pipe sizing can affect chiller performance. Many technicians attempt to upgrade a system using existing piping runs, but this practice can affect system pressure, resulting in fluid flow issues. The end result is improper cooling for the application.
Selecting a process pump that allows a balance between chiller and process requirements can be critical. A good choice may be a system design that utilizes two pumps, one allowing smooth, efficient chiller operation, and another providing stable temperatures and fluid flow rates to the process application.
A system using glycol for lower ambient applications also can be a challenge. Glycol and other additives influence the cooling ability and service-pump capacities of any chiller system. It is wise to take precautions when initially sizing the chiller system. The higher the concentration of the additives, the less cooling capacity of the chiller. Because of viscosity changes in the system's fluid, service pumps tend to lose some capacity as well. Again, the chiller supplier can assist in pump selection.
Some technicians like to oversize a chiller to ensure reserve capacity for future system changes or to overcome the effects of glycol. But this should be done with caution. Oversizing without regard to design limitations can cause excessive cycling, contributing to losses in energy efficiency, increased maintenance, decreased compressor life and burned contacts. All this costs money in the long run.
Sizing the chiller correctly and taking a small amount of time to consider all the variables, including those most often overlooked, can save end-users a headache, and more importantly, time and money.
Rex Martin is product manager at Tecumseh Compressor Co., Cooling Products Div., Clinton, Mich., a supplier of refrigeration compressors and condensing units, evaporator eoils, chilled water refrigeration units, cooling towers, and replacement parts. For more information, call (866) 654-8567 or visit www.tecumsehcoolproducts.com