Okay, let's break down your plan for adding GFCI protection to your bath fan/light combo located in the shower, while keeping the rest of the bathroom lights separate. Your approach is generally sound, but there are some very important considerations and details to get right for safety and proper function. Let's go through it step-by-step

Understanding the Goal
Safety First

The goal is to protect the exhaust fan/light within the shower enclosure with a GFCI device. This is essential for safety.

Selective Protection

You want the GFCI to only protect the fan/light, so if it trips, the other bathroom lights remain operational.

Code Compliance

The NEC (National Electrical Code) requires GFCI protection for outlets in bathrooms, and specifically mentions protection for exhaust fans located within the shower/tub area.

Analyzing Your Proposed Wiring Plan

Let's examine your plan, and point out potential issues:1. Switch Over Switch to Make Room for GFCI

This is a good idea to condense the number of switches. A good option would be a double switch where the two switches are stacked vertically.2.

Neutral Connections



Line Side Neutrals

You are correct in wanting to tie the neutrals from the main feed (cable coming into the switch box), the vanity light switch, and the recessed light switch together and to the line side neutral terminal of the blank face GFCI.

Load Side Neutral

This is where it gets very important. The neutral from the 3-wire cable going to the exhaust fan/light must be isolated. It must connect only to the load-side neutral terminal of the GFCI. Do NOT tie it to any other neutral in the box. Reason: GFCI devices work by detecting current imbalance between the hot (ungrounded) and neutral (grounded) conductors. Any current flowing through a different path (like to ground) is a fault, and the GFCI trips. If you connect the load-side neutral to the line-side neutral, the GFCI will immediately trip as soon as you turn the fan or light on, because the GFCI will see the load of the exhaust fan as a ground fault.3.

Hot (Black) Wire Connections



Line Side Hots

As you mentioned, pigtail the black wire from the feed and connect it to the vanity light, recessed light and to the line terminal of the blank face GFCI device.

Load Side Hot

Take the black wire from the load side of the GFCI and run this wire to the line terminal of the double switch.4.

Fan/Light Wiring to the Switch Over Switch

Connect the black wire from the 3-wire cable to one switch and the red wire from the 3-wire cable to the other switch.

Revised Wiring Diagram (Conceptual)

Here's a conceptual outline, and it's strongly recommended you draw this out physically on paper before starting: Incoming Power (Feed Cable)



Black (Hot)

Pigtail it to feed the: Vanity light switch. Recessed light switch. Line terminal of the GFCI.

White (Neutral)

Connect it to the: Vanity light switch neutral. Recessed light switch neutral. Line neutral terminal of the GFCI.

Bare/Green (Ground)

Connect this to the metal box (if applicable) and to the grounding screws on each switch and the GFCI. This is crucial for safety.

GFCI Device (Blank Face)

Line Terminals: Connected as described above (hot and neutral from the feed). Load Terminals:



Hot (Black) to Switch Over Switch (line terminal).

Neutral (White) only to the white wire of the 3-wire going to the fan/light. 3-Wire Cable to Fan/Light



Black Wire

Connects to one of the switch poles of the switch over switch.

Red Wire

Connects to the other switch pole of the switch over switch.

White Wire

Crucially, connects only to the load-side neutral terminal of the GFCI.

Bare/Green (Ground)

Connects to the ground terminal in the junction box at the fan/light and to the fan/light's grounding point.

Important Considerations & Warnings 3-Wire Cable

Ensure you are using appropriate gauge wire (usually 14 AWG, but check your local codes). Make sure the cable is rated for the environment (moisture, etc.)

Grounding



Proper grounding is essential! Ensure the metal box is grounded (if applicable), and that all devices (switches, GFCI) are grounded.

Box Fill

Make sure the box is large enough to accommodate all the wires and devices. Overfilling a box is a fire hazard and a code violation. If it's too crowded, replace it with a larger box.

Wire Nuts/Connectors

Use properly sized and rated wire nuts or connectors. Make sure the connections are secure.

Testing

After wiring,

thoroughly test the GFCI. Press the "test" button. It should trip immediately. Then, press the "reset" button.

Local Codes

Always adhere to your local electrical codes. They supersede any general advice.

Permit

Check if a permit is required for electrical work in your area.

Professional Help



If you are at all unsure about any of this, hire a qualified electrician. Electrical work can be dangerous, and mistakes can be costly or even life-threatening. It's better to be safe than sorry.

SummaryYour plan is good, but the crucial point is to isolate the load-side neutral of the GFCI so it only* connects to the neutral of the 3-wire cable going to the fan/light. Do not connect the exhaust fan’s neutral with any of the other neutrals in the switch box. Get the grounding right. If you are uncomfortable with the work, seek professional assistance. Flag for review