Is a Molded Case Switch just a switch? Can it ever trip like a circuit breaker?
Siemens Molded Case Switches will trip instantaneously on a short circuit condition. This self-protecting element is necessary in order to allow a Molded Case Switch to be applied at a useful short circuit level. Without this element the switch would be limited to applications where the available fault current is approximately 10kA. With this element the switch may be safely applied on systems with available fault currents up to 200kA. The only exceptions are the Siemens SBN and the TD frames, which are listed as ‘Non Automatic Molded Case Switches’ and do NOT have a self-protecting trip element. These frames have a withstand rating that must be matched to the available fault current. The table in Siemens 2004 SPEEDFAXTM, page 6-62 lists the available frames and their self-protecting override levels.
