In the sub-panel I checked all the wires (all the white wires to the bus bar, the 2 black cables, the black cable with the yellow stripe, even the black wires going to the breakers). None of them appeared loose.
In the main panel I just checked the 2 black cables. Is there another one in the main panel I need to check?
In the main panel I just checked the 2 black cables. Is there another one in the main panel I need to check?