How To Wire A Bathroom Exhaust Fan With Light And Heater

Dennis Howard
by Dennis Howard

That combination light, heater, and fan in your bathroom has finally gotten so noisy that you can’t stand it anymore. Working with electrical circuits in your home is usually a job for a trained and licensed electrician. However, if you are replacing an existing unit, this project is well within most homeowner’s abilities.

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Replacing an existing bathroom combination exhaust fan requires several steps and a few simple steps.

  • Gather the tools
  • Remove the old combination unit
  • Install the new unit
  • Test the new unit

Several intermediate steps for each of these items are discussed in this article.

Removing an old exhaust fan unit and installing a new unit can be a satisfying project. There are some caveats and cautions of which you should be aware. We cover these issues in detail in this article.

Before You Begin

Working with electricity is dangerous. The voltages and amperages in your home electrical system are potentially deadly. If you are not comfortable working with electricity, you should find a qualified electrician to make the change in your bathroom.

Getting Ready to Make the Change

Let’s get ready to change the combination exhaust fan in your bathroom. Properly preparing will make the installation much easier and keep your frustration level to a minimum.

Step 1 – Gather the Materials

There are a few things you will need to make this job much easier. Gather your tools and materials before you begin.

  • Gather your tools. The installation instructions that came with your new exhaust fan unit will give you a list of tools and materials.
  • Electrical tape and wire nuts if not included in the packaging. Most new exhaust fan kits will include the wire nuts.  You can also save the wire nuts when you take down the old unit.  Electrical tape is always handy to have around when doing any wiring.
  • Have the new exhaust fan in hand. Don’t take down the old fan without having your new fan ready.  You want to avoid leaving exposed wires for any period.
  • A step stool or ladder. Most of us are not tall enough to work on a ceiling-mounted fixture while standing on the floor.  Be safe and use a step stool or ladder meant for this purpose.  Do not stand on the toilet, a chair, or anything else not meant for climbing.
Step 2 – You Are Going to Need Light

If your bathroom doesn’t have a window, when you take down the light, it is going to get dark. Plan to have a secondary light source in the bathroom

Step 3 – Turn Off the Electricity for the Bathroom at the Circuit Breaker

Locate the breaker in the service panel in your home that protects the bathroom circuit. It is critical that the correct breaker is off and that the circuit that feeds the exhaust fan unit is not powered. Failing to perform this step can lead to some painful lessons.

Making the Change – Out with the Old and in with the New

Wiring a new exhaust fan with a heater and a light requires an understanding of how the electrical circuits control the fan, heater, and light. The first step is to look at the old exhaust fan wiring

Step 1 – Examine the Old Wiring

Look at the way your old exhaust fan. You need to look at the switches in the bathroom and the wires attached to the old fan unit. There are several variations that you may find in your bathroom.

  • A Switch for Each Function – If there is a switch for each function, light, heat, and fan, there may be several wires attached to your exhaust fan unit. Typically, there is a white wire and several black wires.  The trick is figuring out which wire controls which function.
  • A Switch for the Light and Fan and Separate Switch for the Heater – In some installations, the fan comes on when the light comes on. Again, you must determine which wires are controlled by which switch.
  • Only One Switch and Two Wires – If you find only two wires attached to your exhaust fan, the situation is much different. In this case, you must add additional wiring to your bathroom system, and this requires a licensed electrician.

Step 2 – Disconnect the Old Wires

As you remove the wires from the old exhaust fan, we suggest that you label each wire as it is disconnected. Labeling wires is especially important if the wires are not color-coded. As you disconnect the wires work systematically. Remove one wire at a time and replace the wire nut on the wire of your home electrical system. Replacing the wire nut is a safety function for your protection.

Step 3 – Reconnecting the wires

You must know which wire connects to which switch. Otherwise, you may inadvertently connect the wrong function of the heater to the wrong switch. This is particularly important if the heater on your exhaust fan has a separate circuit than the one that serves your light and fan.

Work methodically and reconnect one wire at a time. Typically, you must connect white wires to white wires and black wires to black wires. However, the wiring in your house may not conform to these standards and great care and you must be careful to make the connections correctly.

Step 4 – White to White

Several white wires from your exhaust fan may connect to a single white wire in your electrical circuit. A common connection is normal and makes things a bit easier. Connect the white wires from your exhaust fan to the common white wire in your electrical system. Use a wire nut and not just electrical tape.

Step 5 – Black to Black, Maybe

There should be several black wires feeding into your exhaust fan unit. These wires carry the current to the fixture and must connect to the correct wire on your exhaust fan.

Typically, each function of your combination exhaust fan unit will have a separate electrical feed. These wires on your exhaust fan unit are usually color-coded. Refer to the installation manual that came with the unit to determine which wire controls each function

The black wires are called hot wires and deliver the electricity to your new exhaust fan, light, and fan. Unless you know which switch each black wire connects, you may not connect the correct function to the correct switch.

Step 7 – Test and Confirm

Turn on the circuit breaker at the service panel. If the circuit breaker immediately trips and opens the circuit, this is an immediate indication that something is amiss with your wiring system. Leave the break open and make sure that you have the exhaust fan unit wired correctly.

If the circuit breaker doesn’t tip, return to the bathroom, and test each function separately. Turn on each function of your combination exhaust fan at a time. If these all work as expected, turn them all on at the same time. If you don’t get a circuit breaker trip, everything is functioning correctly.

If the circuit breaker trips with the light, heater, and fan all working at the same time, your wiring may not be large enough to handle the load. At this point, you should consult with a licensed electrician for a solution.

Beyond the Simple Installation

Your old exhaust fan may have been just that, an exhaust fan. In some instances, the exhaust fan in your bathroom is wired to the light fixture and controlled with one switch. When the light is on, the fan is on as well. Having the fan wired directly to the light may not be an ideal situation.

If you elect to replace your old exhaust fan with a combination unit that includes a heater and a light, you will probably need to add additional wiring and switches to control all the heater, light, and fan separately.

Unfortunately, most homeowners and DIY’ers should not attempt this kind of upgrade. This project requires a licensed electrician who has the skills and knowledge to do the work safely and correctly.

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Upgrades and Updates

It doesn’t matter the reason for updating or upgrading your existing bathroom ceiling fan. The project is doable by someone with basic skills and understanding of home electrical wiring. However, there may be a time when you need to seek the help of a licensed electrician. Never compromise your safety, the safety of your family, or risk damaging your home by performing repairs or updates for which you are not qualified.

Dennis Howard
Dennis Howard

Dennis is a retired firefighter with an extensive background in construction, home improvement, and remodeling. He worked in the trades part-time while serving as an active firefighter. On his retirement, he started a remodeling and home repair business, which he ran for several years.

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