If one breaker will not close when the other is open, some possible causes are:
- a shunt trip being energized or an UVR not being energized
- the red reset button has not been pressed in
- A lock is in place or an interlock is not made up
- the cables are out of adjustment, or bend radius is too tight, or dirt/corrosion has made them difficult to move
The most likely cause relates to the adjustment of the cables. The interlocks should be inspected for tolerances at the attachment points and ensure minimum bend radii are maintained per the instruction bulletin for the cable interlocks. Over time, dusty, corrosive, or wet environments can also impact the free movement of cables within the sheath and inhibit transfers.