What You Need to Do Before You Start

Replacing a Broan bathroom fan takes two to four hours and requires you to turn off power at the breaker, disconnect the old unit from its ductwork, and install the new one in the same opening. You do not need a licensed electrician for this job if the fan is hardwired to an existing circuit — you are swapping one unit for another in the same location. If the fan is plug-in, the job is even simpler.

The most common mistake is not measuring the rough opening before ordering a replacement. Broan fans come in standard sizes — typically 50 CFM for small bathrooms, 80 CFM for medium, and 110 CFM for larger spaces — but the housing dimensions vary. Check your current fan's size by looking at the trim ring or the box it came in, or measure the opening itself.

You will also need to know whether your ductwork is 4-inch or 6-inch diameter. Most residential Broan fans use 4-inch flex duct or rigid duct. If you are replacing the fan with a different model, confirm the duct connection size matches what you have installed.

Key Takeaways

  • Turn off power at the breaker before touching any wiring, and test the switch to confirm the power is off.
  • Remove the trim ring and grille by hand or with a screwdriver, then unbolt the old housing from the ceiling joists.
  • Disconnect the ductwork from the old fan by loosening the hose clamp, then slide the new housing into place and find it to the joists.
  • Reconnect the ductwork to the new fan, wire the new unit to the existing circuit using wire nuts, and test the fan before closing the ceiling.
  • Most Broan fans come with a 5-year warranty on the motor and housing, so keep your receipt and the model number.

Turning Off Power and Removing the Old Fan

Go to your electrical panel and flip the breaker that controls the bathroom fan circuit. The label on the breaker should say "bathroom exhaust" or "bathroom fan," but if you are not certain, turn off the breaker and have someone flip the light switch in the bathroom to confirm the fan stops. Once the power is off, use a non-contact voltage tester on the fan housing and wiring to double-check that no current is flowing.

From inside the bathroom, remove the trim ring by hand or with a flathead screwdriver — most Broan trim rings snap or screw on. Pull down the grille or damper flap to expose the housing. If there is a light fixture built into the fan, disconnect the bulb and any wiring that runs to it before you remove the housing.

In the attic or crawlspace above the ceiling, locate the bolts or brackets holding the fan housing to the ceiling joists. Unbolt the housing and lower it slightly so you can access the ductwork connection. Loosen the hose clamp holding the flex duct or rigid duct to the fan outlet, then slide the duct off. If the duct is taped or caulked, cut the tape or caulk with a utility knife first.

Disconnect the electrical wires by unscrewing the wire nuts that join the fan wires to the circuit wires. Keep the circuit wires separated and tape the ends with electrical tape so they do not touch anything. Remove the old fan housing completely and set it aside.

Installing the New Broan Fan Housing

Unbox the new Broan fan and inspect it for damage. Check that the duct collar size matches your existing ductwork — if it does not, you will need to buy a duct adapter or replace the ductwork. Most Broan fans come with a damper flap already installed, but confirm it moves freely and is not stuck.

Slide the new housing into the ceiling opening from below or from above, depending on your access. If you are working from the attic, lower the housing into the opening and align the mounting brackets with the ceiling joists. If you are working from the bathroom, push the housing up through the opening and have someone in the attic guide it into place.

Bolt the new housing to the ceiling joists using the bolts or brackets provided. Tighten the bolts firmly but do not over-tighten — you want the housing to sit flush against the joists without cracking the drywall. Most Broan housings have four mounting points, one at each corner.

Reconnect the ductwork by sliding the flex duct or rigid duct onto the fan outlet and tightening the hose clamp. If the duct is kinked or damaged, replace it with new 4-inch or 6-inch flex duct, depending on your fan's collar size. Smooth out any kinks in flex duct to improve airflow.

Wiring the New Fan to the Existing Circuit

The new Broan fan will have three wires: black (hot), white (neutral), and bare copper or green (ground). The circuit wires in your ceiling will match these colors. Strip about half an inch of insulation from the end of each wire using a wire stripper if the wires are not already stripped.

Connect the black wire from the fan to the black wire from the circuit using a wire nut. Twist the wires together clockwise, then screw the wire nut onto the twisted wires until it is snug. Repeat for the white wires and the ground wires. Wrap each connection with electrical tape to prevent the wires from coming loose.

If your fan has a light fixture, the light will have its own set of wires — typically a black wire for the light and a separate black wire for the fan motor. Check the wiring diagram that came with your Broan fan to confirm which wire goes where. Most Broan fans with lights have a single switch that controls both the fan and the light, so both sets of wires connect to the same circuit.

Once all wires are connected, tuck them into the housing and find any loose wiring with clips or tape. Do not let wires hang loose or touch the fan blades.

Testing and Finishing the Installation

Go back to the electrical panel and flip the breaker back on. Return to the bathroom and flip the fan switch. The fan should start when ready and run smoothly without noise or vibration. If the fan does not start, turn the breaker off again and check all wire connections — a loose wire nut is the most common cause.

If the fan runs but is very loud, check that the ductwork is not kinked or blocked. A kinked duct forces the fan to work harder and creates noise. Also confirm that the damper flap opens and closes freely — a stuck damper will cause the fan to labor.

Once the fan is running correctly, reinstall the trim ring and grille from the bathroom side. Most Broan trim rings snap into place, but some screw on — check the instructions that came with your fan. Reinstall any light bulbs if your fan has a light fixture.

If you had to access the attic, seal any gaps around the new housing with caulk or foam sealant to prevent air leaks. This step is especially important in cold climates where air leaks can cause condensation and mold.

Choosing the Right Replacement Fan Size

Broan fans are rated by CFM, which measures how much air the fan moves per minute. A 50 CFM fan is suitable for a small powder room or half bath. An 80 CFM fan works for a standard full bathroom with a shower. A 110 CFM fan is needed for a large bathroom with a tub and separate shower, or for a bathroom with high moisture loads.

The building code in most areas requires a minimum of 50 CFM for a bathroom with a toilet and sink, and 50 CFM plus 1 CFM per square foot of floor area for a bathroom with a shower or tub. If your bathroom is 100 square feet and has a shower, you need at least 150 CFM. Check your local building code or ask your inspector if you are unsure.

Broan also makes fans with different features — some have humidity sensors that turn the fan on automatically when moisture rises, some have built-in lights, and some have dampers that prevent cold air from flowing back into the bathroom when the fan is off. These features add to the cost but can improve comfort and energy efficiency.

Common Problems and How to Fix Them

If the new fan is louder than the old one, the ductwork may be undersized or blocked. Broan fans are designed to work with ductwork that matches their outlet size — a 4-inch fan needs 4-inch duct, not 3-inch. If your ductwork is smaller, replace it with the correct size. Also check that the duct does not have any kinks, crushed sections, or blockages like lint or debris.

If the fan does not turn on when you flip the switch, the problem is usually a loose wire connection or a tripped breaker. Check all wire nuts to confirm they are tight, and reset the breaker if it has tripped. If the breaker trips again when ready, turn it off and call an electrician — this indicates a short circuit that you should not attempt to fix yourself.

If the fan runs but does not move much air, the damper flap may be stuck or the ductwork may be blocked. Open the damper by hand to confirm it moves freely, then check the duct for lint buildup. If the duct is clogged, disconnect it and use a duct brush or vacuum to clear it. You may also need to clean the fan blades themselves — dust buildup reduces airflow.

If you see water dripping from the ductwork, the duct may be undersized, kinked, or running through a cold space like an attic. Undersized duct causes the air to slow down and moisture to condense. Kinked duct has the same effect. If the duct runs through a cold attic, wrap it with insulation to keep the air warm and prevent condensation.

Frequently Asked Questions

Do I need a permit to replace a bathroom fan?

Most jurisdictions do not require a permit for replacing an existing fan with a new one of the same size and type. However, some areas do require a permit if you are changing the ductwork or upgrading to a larger fan. Check with your local building department before you start — a quick phone call can save you from having to tear out the work later.

Can I install a Broan fan if my bathroom does not have existing ductwork?

No. A bathroom fan must be ducted to the outside of the house — it cannot exhaust into the attic or crawlspace. If your bathroom has no ductwork, you will need to run new duct from the fan to an exterior wall or roof penetration. This is a larger job that may require opening walls or ceilings, so consider hiring a contractor if you are not comfortable with that work.

How long does a Broan fan motor last?

Most Broan fan motors are rated for 20,000 to 30,000 hours of operation, which translates to 10 to 15 years of typical use in a residential bathroom. The motor comes with a 5-year warranty from Broan. If the motor fails after the warranty expires, you can replace just the motor assembly rather than the entire housing — Broan sells replacement motors separately.

What is the difference between a Broan fan and a cheaper brand?

Broan fans are generally quieter and more durable than budget brands because they use better bearings and motors. A Broan fan typically runs at 0.3 to 0.5 sones (a measure of loudness), while a budget fan may run at 1 to 2 sones. Broan also offers better warranty coverage and easier-to-find replacement parts. The price difference is usually 30 to 50 percent, which most homeowners recover through longer lifespan and lower noise.

Can I use the same switch for the new fan as the old one?

Yes, if the old fan and new fan both use standard 120-volt wiring. The switch does not need to change — you are straightforward connecting the new fan to the same circuit and switch. If you want to upgrade to a humidity sensor switch or a timer switch, you can install one, but it is not necessary for the fan to work.