Bathroom Vent Fan with Light Wiring Diagram | Single vs. Dual

Vent fan and light combinations run on one switched hot for combined control, or two for independent control, plus a shared neutral and ground.

Buying a combination vent fan with light is the easy part. Wiring it so the fan and light turn on together — or from separate switches — trips up plenty of DIYers, because the conductor count in the wall changes depending on which control you want. Here’s the wiring pattern behind it, what changes between single- and dual-switch setups, and the installation steps that matter.

How a Bathroom Vent Fan with Light Is Wired

A bathroom vent fan with light uses a shared neutral and ground, with one or two switched hot wires depending on how you want to control it. The matching unit leads are simple: the hot wire connects to the fan motor lead, the light lead is usually red or blue, all white neutrals tie together, and the green or bare ground bonds to the housing.

The core pattern stays the same across most Broan-NuTone models:

• Black or switched hot to the fan motor lead.
• Red or blue lead to the light fixture.
• White neutral tied to the supply neutral.
• Green or bare ground bonded to the housing.
• All splices enclosed in the junction box, with the cable routed so it never touches the unit sides or top after installation.

Broan-NuTone’s 744L installation guide shows this exact layout, including a red lamp lead connected to the lamp wiring plate.

Single-Switch vs. Dual-Switch Control

The difference between the two setups is entirely in how many switched hot conductors run from the wall switch box to the fan location. Single-switch wiring uses one switched hot, so the fan and light always operate together; dual-switch wiring adds a second switched hot for independent control.

That second conductor is the reason a pre-existing single-switch setup often can’t support independent fan and light control. If your wall only has a single cable, adding independent control means pulling new wire.

Installation Steps and Common Mistakes

Safe installation follows a fixed order: turn off power at the breaker, run 120 VAC house wiring to the fan location, connect supply neutral to unit neutral, connect switched hots to the matching unit leads, connect ground, reinstall covers, and restore power to test.

Three safety rules matter before anything else. Power must be off at the breaker before opening the junction box. The duct must vent to the outside — never into an attic or enclosed space. And branch-circuit wire must meet the product’s minimum, which for one Broan-NuTone manual is 14 AWG.

The most common failures come down to a few avoidable errors:

• Matching the wrong switched hot to the light lead.
• Skipping the ground connection.
• Using too few conductors for separate fan/light control.
• Leaving splices exposed outside the box, or letting cable rest on the housing.
• Confusing a fan/light combination ventilator with a heater/fan/light unit, which needs different conductors and switch logic.

Every connection should be double-checked against the wiring diagram in your model’s manual before restoring power. When the breaker flips back on, each switch should control exactly what you intended. If you’re still choosing a unit rather than installing one, our rundown of the best bathroom vent fans with lights compares the models worth your money.