This issue is commonly raised on three-phase Series 300 Group 1 units installed with the retrofit Group G controller. The legacy ASCO Series 300 in Group 1 only has two sensing leads on the Emergency source side tapped to the A and C poles. Hence, if the retrofit Group G controller is set to three-phase sensing for the Emergency source, the controller will get incorrect readings on the Vab and Vbc values due to the missing sensing lead on the B pole of the Emergency source and would consequently take the Emergency source as unacceptable.
The corrective action to take is to set the Group G retrofit controller to single-phase sensing for the Emergency source, that is, set S1 actuator 9 to OFF while keeping S1 actuator 8 to ON for three-phase sensing on the Normal source side. All other DIP switches and the jumper card must be adjusted to match the voltage of the target unit.
Published for:ASCO Power Technologies USA