Your Aging Three-Phase UPS: When to Refresh, Replace or Run to Fail

Overview

UPS failures account for about one quarter of unplanned data-centre outages. The paper explains wear-out mechanisms (dust, humidity, heat), citing a nominal UPS environment of 72 F (22 C) and 50% RH. It distinguishes design life, service life and recommended replacement time and tabulates them (replacement/service/design, years): VRLA 4/5/10, wet cell 12/15/20, lithium 10/12/20, external capacitors 7/8/15, capacitors in power modules and electronic boards 10/11/20.

Three options are weighed: full replacement, a service-life extension that replaces internal electronics in the existing frame (stated to give about 10 additional years of operation), and running to failure.

A worked comparison quantifies the replacement of a legacy 750 kVA unit. New UPSs run at 94-99% efficiency against 80-92% for most legacy units. At 750 kVA and 30% load, legacy is 89.8%, modern double conversion 96.3%, VMMS 96.7% and ESS 99.2%; ESS saves about $23k per year in power and cooling.

Key points

1. UPS failures account for about one quarter of unplanned data-centre outages.
2. Nominal UPS environment is 72 F (22 C) and 50% RH; dust, humidity and heat accelerate wear.
3. Replacement/service/design life (years): VRLA 4/5/10; wet cell 12/15/20; lithium 10/12/20; external capacitors 7/8/15; power-module capacitors and boards 10/11/20.
4. New UPSs run at 94-99% efficiency versus 80-92% for most legacy units.
5. 750 kVA at 30% load: legacy 89.8%, modern double conversion 96.3%, VMMS 96.7%, ESS 99.2%; ESS saves about $23k per year.
6. A service-life extension of internal electronics gives about 10 additional years of operation.

Using it in design

• In the asset/lifecycle module store the installation year per UPS and battery, and project replacement dates from the component table defaults.
• Flag UPSs older than 10 years and VRLA batteries older than 4 years.
• In the energy model compare legacy and replacement efficiency at the actual load fraction, including cooling energy for UPS losses.

Who should read it

Facility owners managing UPS fleets past ten years and engineers deciding on refresh.

Related standards

• IEC 62040-3
• NFPA 70B

Publication details

Authors

Stephen Gould

Publisher

Eaton

Year

2021

Document number

WP161005EN

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation