The ideal environment for an uninterruptible power supply (UPS) and its associated battery pack would be a safe, dust-free, dry room with an ambient temperature of 20-25 °C and adequate airflow to meet the manufacturer’s requirements.
When installing a UPS as part of a new build project or renovation work, the environmental requirements are usually carefully considered and the UPS is placed in an ideal location to increase reliability and maximise uptime.
Sometimes, when a UPS is retrofitted into existing electrical infrastructure, the ideal environment is often not physically available. With poor planning, designers place UPSs alongside other electrical equipment, such as switchgear, located in industrial premises, basements or even outdoor containers. The UPS may then have to contend with harsh environmental elements. If this is the case, how can the impact of a harsh environment be mitigated?
Separate Battery Location
Most UPS models are specified to operate between 0C and 40C (assuming no condensation); within this range, the UPS will operate without serious impact on its overall lifetime, provided that consumer components such as capacitors are preventively checked and replaced if necessary. Batteries, however, are a different story. Although the specification sheets indicate a similar lifetime, the lifetime and performance vary dramatically depending on the temperature.
Most battery manufacturers specify performance characteristics and lifetime at 20C on their specification sheets. At higher temperatures, performance will increase but lifetime will decrease. At lower temperatures, lifetime will increase but performance will decrease
Dust Filters
In normal operation, the UPS is always running, so there is a constant flow of air in and out of the system. If there is a lot of dust or other airborne particles in the environment, the inside of the UPS can become clogged, not only causing cooling problems but also coating the internal components with debris and potentially causing damage. Selecting UPS that are equipped with dust filters as standard, or that have the option of retrofitting and replacing them regularly, will prevent the harmful accumulation of dust inside the UPS that compromises system reliability. In particularly harsh environments, a “conformal coating” may also be recommended, see below.
Conformal Coating
As mentioned above, ambient air (and associated airborne particles) continuously blows through the UPS throughout its lifetime. Where the air may contain moisture, chemical contamination or high humidity levels, some manufacturers offer the option of applying a ‘conformal coating’ (sometimes called topicalization) to the internal circuitry. A conformal coating is a protective chemical coating applied by the manufacturer before shipment. Being electrically insulating, it maintains the surface insulation resistance for a long time, thus protecting the electronic assemblies from airborne contaminants such as salt spray, which helps to prevent corrosion. This procedure was historically used for ‘industrial’ UPSs, but now manufacturers such as Huawei and AEC use this technology as standard equipment in their three-phase UPSs.
Summary
Cooling fans degrade over time and have a lifetime of approximately five to seven years under good environmental conditions; it is rare for a fan to fail before this time, but if it does it should be replaced as soon as possible.
Arranging for preventive replacement of all cooling fans at set intervals is the most cost-effective method, saving labor costs and organizing maintenance windows. It is also the best way to increase the reliability of UPS operations by reducing the possibility of a loss of added load and costly downtime.
