I recently purchased a house that is serviced by a well. The pressure tank is located outside next to the house in a small shed. The previous owner wired a receptacle into the square-D pressure switch to allow them to power a light bulb to keep the pipes from freezing. The circuit is protected by a 30 amp double pole breaker and the problem/issue is that I'm not sure they had it wired correctly. The connected the black wire to the L2 post of the Square-D pressure switch and the ground and white wire to ground in the switch from the receptacle. I have disconnected the receptacle until I can verify that it was correct and safe. Is this correct or a common practice in these type situations?

If the neutral of the outlet was using the ground from the well pump feeder cable, that cannot be done.