Trying to replace an old outlet in my kitchen with a GFCI outlet. The outlet has two lines in the outlet box. the first line has black, red, white, and ground while the other line has white, black, and ground. The red from the first line is spliced to the black from the other line. See pictures:
How do I actually wire this setup to the back of the new GFCI outlet? I first connected the black and the white to the line in and connected the solitary white to load and it kept tripping the breaker on the plug.
So I disconnected the solitary white and the plug works but a different plug in the kitchen then does not work. I'm not sure what the red/black splice is doing. I know a red can mean a switch is involved but there is only one switch nearby and it controls the garbage disposal and is on a completely different breaker. Any help would be greatly appreciated.