What are Environmental Conditions for an Uninterruptible Power Supply (UPS)?


external air conditioning units for comms roomAll UPS manufacturers will quote a maximum operating temperature for their equipment (typically +40C). The air conditioning plant must have sufficient capacity to maintain the conditions stated.  Obviously the overall efficiency of the UPS will have a significant effect on both the size and the operating cost of the air conditioning plant. The high efficiency figures (up to 97%) quoted for modern on-line UPS from some manufacturers, can mean no additional air conditioning is required.
Likewise, if the UPS batteries are installed in the same room as the UPS, be sure to check that your intended air cooling system is able to keep the ambient temperature at a level suitable for the batteries.

Make sure to NEVER:

  • allow the environment of your UPS system to be consistently above 22 degrees Centigrade
  • overload a UPS
  • allow the UPS to run with imbalanced phases i.e. a 3 phase UPS MUST have its load balanced across the 3 phases
  • put objects on top of a UPS
  • block the fans
  • place a UPS underneath an A/C unit
  • put a UPS in direct sunlight or next to any source of heat
  • place a UPS in any area susceptible to flooding or dampness


Again the UPS manufacturer will state maximum permissible relative humidity levels (typically 95%). Certainly high relative humidity levels promote corrosion of cabinets and internal parts. Simple dehumidification equipment is available for sites where this may be a problem, although air conditioning will generally already dehumidify the air at the same time as cooling it.

Audible Noise

The unit of sound intensity is the decibel (dB). It represents the ratio between the sound level measured with a microphone and a reference sound level (Odb), therefore defined to be approximately equal to the threshold of human hearing. However, the human ear is less sensitive to very low and very high frequencies. When measuring background or other intrusive noises, an additional ‘A’ Filter is applied. This is why all UPS manufacturers use the dBA unit.

Typical audible noise figures for fully loaded UPS equipment range from 50dBA for 5kVA to 60dBA at 60kVA.

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