Dell UPS 4200R - Manual (Page 23)

21 Installation and Startup |
Starting the UPS
1 Verify that all load segment circuit breakers are in the ON position.
2 For 3750W/208V models only.
Verify that the power input to the UPS has a minimum of 30A
upstream overcurrent protection.
3 For hardwired input models only.
Switch the main utility breaker on.
4 Press the button on the UPS front panel.