Originally Posted by Stratmando
Yes, plugging into the 2 slots should read 120 volts, you should also be able to measure 120 volts between the small slot(hot) and the bigger ground hole. You should have no voltage between the Big sllot(neutral) and ground, as they are connected together at the Service and are at the same potential.
If you have voltage between the ground and the Large slot(neutral( and not the small slot(hot) then polarity would be reversed.
You can't "be certain" it is connected to the Line side, you have to be sure. Good Luck
Many newer GFI's will not trip and reset if no power is going to them.
In fact, I know the outlet in question is the last in the series because it only has one black and one white coming in.