LABC - Registered System Certificate of Conformity

Thermarestor® - Testing

The Thermarestor® system has been specifically designed and developed to act as a pre- ignition solution to the problem of electrical fires resulting from resistive heating due to high resistance connections (HRC) and abnormal heat resulting from prolonged electrical overload.


The TSW thermal switch, the component common to the Thermarestor product range, is manufactured by Vishay Intertechnology Inc. and has already been subject to rigorous testing, as would be expected from one of the world’s leading manufacturers of passive components. The procedures and results contained within this report relate to the independent testing of the engineered applications incorporating the TSW thermal switches and which constitute the Thermarestor system. This testing was carried out by Schneider Electric UK Ltd. at their engineering laboratory in Swindon, being completed in June 2014


The aim of this testing was to establish that the Thermarestor product range functions as intended, namely by sensing abnormal or unexpected heat associated with both HRC and prolonged overload conditions and activating within its set design parameters.


Having concluded the testing phase, the headline results may be summarised as follows:

  • Increased resistance at electrical connection points results in heat being generated (resistive heating).
  • Such heat is confined to a relatively small area i.e. localised heating
  • At maximum operating load conditions the temperatures generated within the consumer unit were not sufficient to cause activation of the Thermarestor System i.e. there would be no “nuisance” activations under normal operating conditions in an “electrically sound” installation.
  • Activations of the TSW switch component were recorded in tests involving the consumer unit and environmental chamber
  • The TSW thermal switch activates in accordance with its design parameters ie. 80°C ± 5. All recorded activations were in the range 80.7˚C to 84.1˚C.