The only way to power clean an Epson R3000 is by using the Epson Service Adjustment Software. We know that it is available from 2manuals.com. You can purchase and download it fro there. It is a Windows only solution. Epson has no Mac solution.
After you download the software:
Make sure that the printer is in the Ready state.
Launch the Epson Service Adjustment Software and click on Particular Adjustment Mode.
Click on Ink Charge on the Maintenance Menu. In the Ink Charge Menu click on the Ink Charge button. The printer will now perform the original ink initialization. It takes several minutes. About 15ml of ink in each position will be charged through the system. Do not interrupt the printer or system. You will see a confirmation that the ink charge has been completed when it is finished.
From this same window you can perform head cleanings and nozzle checks. You may wish to do so. However, if you can not get a clean nozzle check within 3 tries. Allow the printer to settle down for several hours. You can use the regular Epson utiltiy software or the printer's maintenance menu to perform nozzle checks and head cleans.