Use of ICAR Capacitors in uninterruptible power supply (UPS) systems

The Health and Safety Executive (HSE) has issued a safety alert concerning the use of ICAR Capacitors in uninterruptible power supply (UPS) systems. The potential dangers from this safety alert may be fire, and any consequential issues arising from the possible loss of power to connected equipment.

In 2018, a fire occurred in an industrial UPS system. The fire was caused by the dangerous failure of ICAR branded polypropylene capacitors, located in the UPS unit which carry out AC voltage waveform correction.

The HSE have found that another ICAR branded polypropylene capacitor was responsible for a similar UPS system fire in 2011.

Both models of the affected capacitors were by ICAR of Monza, Italy:

  • ICAR LNF-P3B-200-27 (2018 incident)
  • ICAR LNF-P3X-200-38 (2011 incident)


Both capacitors are of polypropylene film construction and are intended to be self-healing if a fault occurs within a discrete area of the capacitor. There is localised heating resulting in internal isolation of the faulty area which allows the capacitor to continue in service.

Self-healing capacitors have a limited life span which can be affected by service duty and ambient temperatures. Methods to identify the need to replace the capacitors may include techniques such as;

  • Capacitance testing
  • Observation of bulging and discolouration.


Dutyholders are advised to take a precautionary approach and consider the replacement of both capacitor models where these have been identified in UPS systems or other industrial equipment.

Dutyholders are also advised to review ventilation and cooling requirements for UPS systems to ensure that acceptable operating temperatures are not exceeded.