Enabled Energy (EE) was engaged to investigate high head alarms occurring on many of the computer room air conditioning (CRAC) units in a Louisville, KY facility. Personnel suggested the alarms may be caused by the inability of the dry-coolers to reject heat on hot days, and therefore are not cooling the glycol enough to prevent high head alarms. Enabled Energy worked with the facility personnel to investigate each possible cause for the alarms. Condensing water (CW) maintenance, refrigerant maintenance, dry-cooler performance, CW loop flow, and CRAC valve modifications were the elements of the investigation.
Enabled Energy’s Solution
Maintenance reports and schedules were provided by the client and were reviewed by Enabled Energy. Trended supply and return glycol temperature and associated outside air temperature data was used to determine the cooling performance of the dry-coolers was adequate. The EE team also employed a three-step process to investigate CW loop flow and then rebalance the system. The steps included:
- Step 1: Field Verification by the client’s team to confirm manual bypass valve positions ahead of EE’s onsite investigation and to install pressure readout ports on any equipment where they were currently not existing.
- Step 2: Loop Measurement and Verification – Working with a certified Test and Balance contractor the EE team confirmed flow and function on each system component. Circuit setters were adjusted, and repair recommendations were reported as required. EE also confirmed the CRAC valve modifications were done correctly and were not a source of bypass flow.
- Step 3: EE provided a full report of the findings, recommendations, and an up-to-date as-built mechanical one line to accompany the report.
The above investigation identified the CRACs were receiving glycol at the rated flow and adequate supply temperatures. It was found that contaminated condensing cooling bundles in the CRACs were causing the heat transfer in the cooling bundles to be inefficient, resulting in high head when water temps rise into the high 90s. The EE team suggested cleaning the loop and cleaning or replacing the condensing bundles in the CRACS. In addition, a few CRAC valves were sticking open and allowing glycol to bypass when the unit was turned off. EE recommended repairing or replacing the valves to reduce bypass flow and save money in reduced pump energy.
Enabled Energy completed the site visit and report in June 2021. EE Fellow and industry expert, Paul Svenkeson, provided expert consultation.