This document provides instructions and specifications for generator sets and their PowerCommand 3100 series controllers. It contains sections on introduction and overview, control operation, circuit boards and modules, troubleshooting, service and calibration, servicing the generator, day tank fuel transfer pumps, initial startup procedures, and an on-site power system application review for diesel generator systems running at 600VAC or lower. The document is an extensive technical manual for servicing and maintaining these generator sets and controllers.