NORTHEASTERN UNIVERSITY SNELL LIBRARY

In 2010, Northeastern University installed a new high-efficiency modular chiller for their Library chilled water plant to supplement an aging centrifugal chiller. Unfortunately, the new chiller had trouble from the initial startup. After months of troubleshooting, the new chiller was set as a backup to limit its runtime unless it was truly needed. In 2015, the University upgraded the existing system pumps to new, high-efficiency variable speed pump skids. When B2Q completed an ASRHAE Level II audit in 2015, we identified that the plant could be running more efficiently and reliably with relatively small controls changes. B2Q recommended revising the pump sequence of operation and the chiller sequencing to capitalize on the part load performance of the modular chiller.

We were hired as design engineers to implement our measures and troubleshoot the modular chiller to get it running for the first time. B2Q identified several sources of the faults, including improperly-wired valve end switches, poor flow balancing between the chillers, and improper programming of the modular chiller's control panel. We also worked with a third party startup technician to diagnose other mechanical issues.

The new sequence of operation was implemented and the mechanical and control issues with the modular chiller were repaired. Since the spring of 2019, the modular chiller has been running successfully as the lead chiller in swing seasons, increasing plant efficiency, reducing demand on building technicians, and extending the life of the older centrifugal chiller.