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Broan Model 688 Replacement Fan

Posted by Robert on Apr 12th 2022

Broan Model 688 Replacement Fan

A Broan bathroom exhaust fan, with time, becomes noisy and leaves your bathroom full of steamy haze on the walls. In such a situation, consider replacing your fan. Here is how to do it.

Tools

  • Drill & Bits
  • Screwdrivers
  • Circuit Tester
  • Screws
  • Duct Clamps
  • Bathroom Exhaust Fan
  • Wire Strippers
  • Work Gloves
  • Roof Vent Cap
  • Utility Knife
  • Wire Connectors
  • HVAC Tape
  • Reciprocating saw
  • Oscillating saw
  • Keyhole saw

Things to consider before installation

1. Determine the Fan Size

If you are replacing an existing fan, the most straightforward way is to use the existing ductwork, switch, and wires. Also, it would be better to acquire a fan that is the same size as the old one so that you don't have to adjust the ceiling or wall hole size.

Fans are rated by sones that measure the noise level, and cubic feet per meter (CFM) are used to measure the airflow. Usually, small bathroom fans are about 50 CFM, while larger ones need around 100 CFM. Significantly, knowing your bathroom's size will help determine the number of CFM you require for a fan replacement. Most companies determine the number of CFM on a cubic feet or square feet basis.

Length x Width x Height = Cubic Feet

Length x Width = Square Feet

Some manufacturers use the formula below to calculate the CFM.

Length x Width x Height x 0.13 = Number of CFM

For example, 10.5 x 8.5 x 6 x 0.13= 69.615 (round up to 70)

Choose a fan 70 CFM or larger.

2. Determine the Exhaust Route

The bathroom exhaust fan needs outside ventilation. If your fan cannot be accessed through an attic, you should vent through a sidewall of your building. These types of vents and ducts are usually fixed during house construction. If it was not in your plan, you need to contact a professional for help.

The fan can vent through either the roof or a gable wall if you can access the attic. Venting the exhaust through an open attic will lead to moisture buildup on the underside of your roof. Also, avoid venting through a ridge vent or soffit vent, as the warm air will enter the attic.

3. Determine Your Electrical Options

It is easier to use the existing switch with your new fan though most fans come with light and can work separately with a double switch or additional switch. However, if your old fan did have a light, you will be required to do new wiring to operate a double switch.

Remove the Existing Fan

Step 1: Switch Off the Power Supply

Turn off the power supply to the fan and remove the grille cover. Use a circuit tester to test that no current flows to the fan entirely.

Step 2: Remove the Motor

Remove the fan motor from its housing. If the motor is fixed using screws, remove the screws and detach the motor from the wiring.

Step 3: Remove the Housing

The fan housing is secured differently as per the manufacturer's design.

  • For a fan held in place with metal, brackets are fixed to the ceiling joists, and you can access the fan through an attic and remove the nails or screws connecting the joists and the brackets.
  • For a fan fixed with mounting screws connected to the ceiling joist, remove such screws.
  • If you can't access the fan through the attic, consider cutting the brackets from beneath using a reciprocating saw or oscillating saw. Do this carefully to avoid cutting the electrical wires.

Step 4: Disengage the Electrical

Detach the electrical connections and rotate the housing in the hole to access the electrical and duct. Pull out the house wire from the fan housing and remove the exhaust duct. Then remove the fan housing from the wall or ceiling.

Method 1: Mounting a Broan Bathroom 688 Fan with Attic Access

When installing a Broan bathroom fan, it is essential to follow the specific instructions in the installation manual. Below are specific steps you should follow if you can access the attic.

Step 1: Modify the Ceiling Hole

Place the housing on the ceiling hole and check if your fan fits. If your home is too small, trace the housing over the ceiling and adjust the hole using a keyhole saw.

Step 2: Patch the Ceiling

If your home is too big, consider patching the ceiling. Get a piece of drywall to adjust the ceiling hole to the required size for your fan. Fix the drywall to a piece of wood, align the hole and join the ceiling into the wood using screws. You can repair the patched area later with a spackling compound.

Step 3: Fix the Duct Connector

Connect the duct connector to your fan housing by sliding it into the slots.

Step 4: Connecting the Housing Brackets

Attach the housing brackets to the ceiling joists from the attic. Normally, the ceiling joists are 16 to 24 inches from one another on-center. Slip the brackets through the slots on the housing and use screws or nails to secure them to the joists. Make sure the fan housing is aligned with the ceiling below. If necessary, use screws to fix the brackets to the housing.

Step 5: Prepare for the Wiring

Pull off the wiring cover on the housing and use a screwdriver to detach the knockout plug.

Step 6: Connect the House Wires

Protrude the house wires through the clamp and fix the screws. Connect the fan wires to the corresponding colors on the house wires using wire connectors or quick connectors. Black is hot and connects to the black house. Green is the earth and connects to the bare copper or greenhouse wire. White is neutral and connects to the white house wire.

If you are using quick connectors, insert the bare wire into the connector, and that's all! For traditional wire connectors, align the two ends of the wire together and win the connector clockwise.

Caution:

Leave it unless the code allows you to cover the connectors with electrical tape.

Step 7: Fix the Wires Back

Push the wires into the fan housing and use screws to fix the wiring cover to the housing.

Step 8: Attach the Duct

Using HVAC (Heating, Ventilation, and Air Conditioning) tape or clamp, secure a 4-inch to the duct connector. If you are not using an attic duct, read the installation process later in this guide.

Step 9: Test the Fan

Switch the power on and check if the fan works. Most fan models are extremely quiet, so you have to listen carefully.

Install the grille by pinching the metal rods together and inserting them into their slots to reinsert the grille cover or tighten the screws holding it in place.

Method 2: Mounting a Broan Bathroom 688 Fan without Attic Access

When installing a Broan bathroom fan, it is essential to follow the specific instructions in the installation manual. Below are specific steps to follow when installing a bathroom fan if you cannot access the fan from the attic.

Step 1: Modify the Ceiling Hole

Place the housing on the ceiling hole and check if your fan fits. If your home is too small, trace the housing over the ceiling and adjust the ceiling hole using a keyhole saw.

Step 2: Patch the Ceiling

If your home is too big, consider patching the ceiling. Get a piece of drywall to adjust the ceiling hole to the required size for your fan. Fix the drywall to a piece of wood, align the hole and join the ceiling into the wood using screws. You can repair the patched area later with a spackling compound.

Ensure that the fan can be fixed using the old fan joists, if not all, at least one joist. If your fan wasn't connected to a joist, attach lumber to the joist if there is a space between the ceiling hole and the joist. Build the lumber next to the hole to allow the fan to be screwed to solid wood.

On the other side of the hole, attach a piece of lumber inside the hole and drive screws through the ceiling such that you have two sides to fix the fan housing.

Step 3: Connect the Duct

Use a clamp or HVAC tape to secure the duct connector to the duct. Ensure you mount the duct in the right position as per the manual to fit the housing correctly. Then connect the duct connector to the edge of the hole using a screw to line it up with the exhaust on the fan housing.

Step 5: Prepare for the Wiring

Pull off the wiring cover on the housing and use a screwdriver to detach the knockout plug.

Step 6: Connect the Cable Clamp

Connect a cable clamp to the hole on the wiring cover.

Step 7: Connect the House Wires

Protrude the house wires through the clamp and fix the screws. Connect the fan wires to the corresponding colors on the house wires using wire connectors or quick connectors. Black is hot and connects to the black house. Green is the earth and connects to the bare copper or greenhouse wire. White is neutral and connects to the white house wire.

If you are using quick connectors, insert the bare wire into the connector, and that's all! For traditional wire connectors, align the two ends of the wire together and win the connector clockwise.

Caution:

Leave it unless the code allows you to cover the connectors with electrical tape.

Step 7: Fix the Wires Back

Push the wires into the fan housing and use screws to fix the wiring to cover the housing.

Step 8: Attach the Duct

Push the fan into the ceiling hole and line up the exhaust with the duct connector. Using screws, fix the fan to the wood supports.

Step 9: Test the Fan

Switch the power on and check if the fan works. Most fan models are extremely quiet, so you have to listen carefully.

Install the grille by pinching the metal rods together and inserting them into their slots to reinsert the grille cover or tighten the screws holding it in place.

Broan is the leader in residential ventilation products, customized climate, and indoor air quality solutions. Find more Broan products here!

Robert Syengo is an experienced web writer with a home improvement history that includes toilet remodeling and appliance installation. He enjoys writing and learning about electronics, gardens, design, remodeling and repair.

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