In this Nationwide Power™ case study, we show the importance of having a qualified Critical Power Professional™ (CPP™) perform maintenance on your critical infrastructure equipment. This case study specifically looks at the Liebert NX 120kVA UPS.
A Nationwide Power CPP was onsite to perform a regularly scheduled preventive maintenance (PM) inspection. During the PM inspection, the CPP noticed that the input voltages were running high, and the output voltages were unbalanced.
| Product | Liebert NX 120kVA UPS |
| Application | Medical Facility |
| Synopsis | During a regularly scheduled PM inspection, high input and unbalanced output readings were found. To further troubleshoot, the uninterruptible power supply (UPS) was placed into maintenance bypass to observe the voltages. No changes were observed and as the unit was being transferred back out of bypass, a short buzzing sound was heard. The transfer had failed, and the critical load was lost. The downtime was further extended because the failure cleared a fuse in the maintenance bypass panel. Site electricians were called in to help repair the bypass panel. After several hours, a replacement fuse was found and installed, and the maintenance bypass was operational again. |
| Preliminary Actions | A Critical Power Professional™ (CPP™)initiated troubleshooting and found 3 blown output fuses, 3 failed static switch silicon controlled rectifiers (SCRs), and a possible bad SCR driver board. Parts were ordered and shipped from Nationwide Power’s inventory via next day air. Upon returning to the site to repair, the CPP replaced all the parts that were ordered. Continuing the troubleshoot, the CPP focused on the output capacitor section, based upon the output voltage symptoms. Additionally, the output capacitors were recently replaced by another vendor who was awarded the job based upon lowest price, and therefore seemed like a logical place to start. |
| Resolution | After in-depth troubleshooting and removing UPS covers, the CPP was able to determine that the capacitor pan assembly wiring harness plug was not plugged into the UPS. After plugging the capacitor pan connector into the UPS and returning all other parts that were removed, the UPS was restarted, with customer approval, and placed back online in normal mode. |
| Root Cause | Human error caused by a simple electrical connection not being completed. Even though Nationwide Power was the service provider contracted to maintain the customer’s critical power infrastructure, a lower price option was selected to replace the UPS capacitors. The quality of service, or lack thereof by the other vendor resulted in the “lowest price” costing an additional $5,000 in repairs. The cost of downtime is not included. Unfortunately, the lowest price is not always the best price, and true cost of total ownership. |
| Additional Reading | https://nationwidepower.com/news/case-study-145-another-reason-why-preventive-maintenance-is-so-important-liebert-nx-40kva/ https://nationwidepower.com/news/case-study-146-when-to-upgrade-or-repair-a-ups-system-eaton-9315-ups-system/ |
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