Brought the pressure up to 250lbs, and searched for the leak in the evaporator using bubbles. The evap coil was exposed and the bubbles were applied to everything including both circuits, thermal expansion valves, cap tubes, end elbows, line sets next to the unit and outside at the condenser. I was unable to detect a leak using the bubbles. I did release the nitrogen (down to 50psi equalized) after the leak search and opened the low pressure switch circuit for the #1 compressor. This was done to protect it from starting while it has no refrigerant. AHU m/n TAA240S4D-1Y S/n 5616B05048