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I have a 20A GFCI outlet that I want to wire a timer to that will control a ceiling exhaust fan. However the timer I have requires connection to a 3 wire (B,W,R-G) box, but the GFCI outlet is only powered by 2 wire (B,W-G); it also services three other outlets. So my question is can I wire the 3-wire timer to a GFCI outlet that is only powered by 2-wire? I've attached a diagram of the timer's wiring configuration.
How does this look for wiring without GFCI protection?
The wiring as shown in the updated diagram is fine.
The red from the timer is the live load for the exhaust fan, i.e. the fan's black. The black of the timer is its power supply, so it needs permanent line feed. You can wire it to the GFCI's line side without protection, or to the GFCI's load side and have protection at the fan.
Since the red in the junction box goes to the fan, the fan will be on the timer.
The remaining black, green and white can be wired as shown:
Generally there is no need for this in a bathroom, but if you want the protected option for the fan, then you would need access to the neutral going to the fan. It should not be wired to the line side neutrals, but instead be wired to the load side of the GFCI. Your updated drawing shows that the required neutral for the fan, and if it's in the junction box then this option is available to you.
It is generally advisable not to have lighting on the protected side, so that tripping the GFCI does not put bathroom visitors in the dark.
To test and verify correct load/line wiring of the GFCI you can apply its test button and confirm that the fan still works and that the downstream outlets have been de-energized.
Your updated diagram is fine.
Read the GFCI instructions for the procedure to attach 2 wires under the Line screw. (they can do that, but tighten HARD).
Note that you are hanging the additional receptacles off the "LOAD" terminals of the GFCI. While the instructions often tell you to do that, it is just as often a mistake. This will cause those other outlets to be protected by this GFCI, which can cause several problems, like them "going dead" for no apparent reason. For this reason you are required to label the outlets "GFCI Protected" using any means you consider aesthetic as long as it is not handwritten. I also advise to state the location of the reset if it is not obvious.
Yes. You have to connect the Load wire, Neutral wire, and Ground to the fan switch from the GFCI outlet side. Connect the Hot wire and Neutral wire to the fan fan timer, this is the power. Connect the Red Wire and Neutral wire to the fan. Be sure all earth grounds are connected.
Yes, you can do it but your diagram is missing the load wires to the fan. You have a black hot, a white neutral and a green or bare ground feeding the GFCI. You can tap off the black, white and green from your timer before they connect to the GFCI, eliminating GFCI protection or tap to the load terminals on the GFCI so the fan is protected (no real reason to protect the fan). Now you need the fan load wire, black to go to the red timer wire, the fan white wire to the group of white wires and the bare copper or green from the fan to the group of ground wires.
The diagram is based on replacing an existing switch in a box with neutral provided, and with a modern (i.e., because neutral included, so 3-wire and white is neutral) switch loop. Which is utterly confusing for your intended use (a new switched device).
Your actual configuration involves three items:
but the diagram pretends it is just two items.
Here is what you need to do:
All grounds always together, to metal box, etc.
