Aircraft Equipment Problem Less Severe
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
Before pushback the APU was started with the GPU. The GPU did not have enough power to start the APU and power the airplane. Power to the airplane was interrupted. We notified Maintenance and they come out and looked at it.  We're not sure if it's related to the event that occurred but might be useful. After takeoff the airplane would not pressurize in the automatic mode. We leveled the airplane at 10;000 and went to the QRH. The airplane would pressurize in manual mode. We contacted Maintenance to see what if they had any input; and they requested we return.  We attempted to burn as much fuel as we could prior to landing but still needed to land overweight. We  used the manual mode to depressurize the airplane during the descent. The Captain made the landing and touched down at 96 feet/minute; well below what was required for an overweight landing.   Threats included the pressurization controller and the possibility in not catching it after takeoff. We noticed it soon enough that oxygen or passenger oxygen was not needed. Other threats included the overweight landing. There were QRH recommendations that were helpful. The situation was handled with the correct amount of urgency. We worked well together to resolve the cabin pressurization issue and the overweight landing. This was a situation where we did not need to rush and make a mistake and therefore we didn't.
EMB145 First Officer reports a power interruption during APU start with a Ground Power Unit. After takeoff the aircraft will not pressurize in the automatic mode and Maintenance Control requests that the flight return.