Dell UPS Rack 2700W HV and problem with communication

Luqa,

The issue you are having may be due to the UPS output voltage being configured inappropriately in relation to the input voltage. The UPS allows a tolerance of +/-6% on the difference between the input and output voltage. When the incoming voltage is too high, the UPS inverter will 'buck' the voltage down to its preset level. Too low it will "boost".

What you will need to do is adjust the output voltage setting on the UPS. This requires that the UPS's output be turned off (UPS in stand-by state) to complete this operation. 

1. From the front LCD, make a note of the input and output voltage.
2. With the mains power still applied, turn the UPS output off by pressing and holding the power-button until the audible beep stops (>3-seconds). The UPS is in standby state when the plug icon changes to a circular power symbol.
3. Press and hold the left pointer button (>1-second) until the UPS enters the menu mode.
4. Select "Settings" and then select "Output Voltage". Press the confirm button to select the option.
5. Use the pointer buttons to change the voltage to closely match that of the input voltage as noted in step 1.
6. Press and hold the confirm button (>1-second) to apply the change.
7. Press and hold the left pointer button (>1-second) as required to quit the menu system.
8. Confirm the changes made by observing the LCD screen. The voltages should match to within +/-6% on the input and output.
9. Power the UPS outputs on by pressing the UPS power button.

Let me know how it goes.