Nema4 4X Lock – April 2010 (PDF)

Peelle has discovered a potential problem with the DC (door closed) contact in the lower box of the Nema 4/4X/7 interlock. if the retaining ring that secures the contact
bar assembly to the contact stud is removed or fails, the contact bar assembly could wedge against the contact point assembly and provide a false DC (door closed)
signal. The issue is similar in the gate contacts listed above except that the signal would be GC (gate closed).