I have an outlet feeding other outlets about 50 feet away. All the outlets are outdoor enclosed in a protective weather cover. Today I wanted to replace one of the receptacles with a GFCI so all the outlets are protected. I installed the wires coming from the power source to LINE and the wires going out to LOAD. As soon as I turned the breaker back on to test the GFCI receptacle, the button trips / shuts off. I have the wires connected to LINE and LOAD properly. Neutrals are connected together and ground is connected. If I only have the LINE wires connected and no LOAD then it works. But if I have the LOAD wires connected to the receptacle, then it trips as soon as I put the breaker back on. What can cause this and how do I go about troubleshooting the problem?
Neutrals shouldn't be connected together with the GFCI. Connect the neutral of the line and load to the appropriate connections on each side of the GFCI. Otherwise, the current will appear to go out via the hot connection and not return via the neutral on the load side of the connection, which is exactly the scenario that the GFCI detects and trips on.
Also, note this important tip from Shirlock, use the push in connectors for the GFCI outlets: When to use holes instead of side terminals to wire an outlet