Influence of RC Element Wiring in Electrical Circuit on Electromechanical Thermostat Contact Wear

Contact wear caused by electric arc during electric contact make (cut-in) and break (cut-out) has the direct impact on the contact lifetime. The RC element wired parallelly to the contact will eliminate or reduce the arcing and subsequently extend the lifetime. Comparative tests of the two sets of identical Danfoss 077B electromechanical thermostats have been carried out. In the first batch, standard thermostats were tested. In the second batch, the same thermostat types, but with RC elements wired parallel to thermostats main contacts were tested. Measurement has not proven any improvement of the contact wear. Temperature drift and change of the critical dimension caused by contact wear were very similar in the both cases. Thus, the application of RC element is considered not reasonable measure for reduction of contact wear of electromechanical thermostats.