UPSB220 Uninterruptible Power Supply Caterpillar

Before beginning this section, complete all sections referenced in Testing and Adjusting, "Basic Preventive Maintenance". Use the following list to verify that the UPS is ready to begin maintenance.

• Verify that the MAINS 1 (Q1) and the MAINS 2 (Q4S) input switches are in the OFF (open) position.

• Verify that the battery disconnects are in the OFF (open) position.

• Verify that the output switch is in the OFF (open) position.

• Unless being used to power the load of the customer, verify that the bypass inputs for the maintenance bypass cabinets are in the OFF (open) position.

• Unless being used to power the load of the customer, verify that the bypass inputs for the UPS isolation switches are in the OFF (open) position.

• Where possible, verify that there is zero ohms continuity between the output neutral, ground, and the frame.

• Install all removed covers that are required to provide safe operation during maintenance procedures before energizing the unit.