How to install Humidifier on a Furnace 

When it comes to home improvement projects, installing a humidifier on a furnace is something you need to do anyway. Although this may seem challenging, after all, you’re not an HVAC expert. However, understanding how to set up a whole home humidifier is important for people living across Canada where indoor air tends to be dry, especially during cold or dry weather. However, the whole process takes minimum effort and time and, at the same time, gives you relief from the chilly environment.

These systems can alleviate dry indoor air conditions caused by forced-air heating units and forced heat pump HVAC systems. By installing a humidifier, you will be amazed at how well they eliminate airborne dust in your home as they bring moisture into the air through vents or ductwork. Once the installation is done, you will feel a more pleasant environment as well as your indoor plants will bloom more than before.

However, humidifier installation generally falls under DIY projects, which also require expertise and skill. With that, installing a whole house humidifier in no time is easy. If you’re new to that or not comfortable with this process, hiring a Smile HVAC expert to do the job would be wise.
Tip: Before going to start the installation process, reading the manufacturer’s step-by-step guide for your particular model is recommended. Also, note that you may need to work with electrical components while installing a humidifier on a furnace.

Tools and Supplies you’ll need for installation:

List of tools

• Level
• Drill and bits
• Aviation Snips
• Marker
• Screwdriver from Philips (flathead)
• Protective gear like gloves
• Adjustable Wrench
• Pliers
• Template or Ductwork (if required)
• Mounting screws and anchor

List of Supplies

• Whole-house or bypass humidifier with placement kit
• Fittings and tubing for drain (if required)
• Water supply line
• Thermostat or low-voltage wire

Important Considerations:

A little preparation is required before installing a humidifier on a furnace or whole-house humidifier. These include:

Tip 1 Look at the wide variety of whole-house humidifiers and choose one that is suitable for your home’s size. However, there are plenty of whole-house humidifiers available in the Canadian market for different home needs.

For those who don’t have a forced-air central heating system that doesn’t feature ductwork, multiple room-sized units or a self-contained whole-house evaporative humidifier are needed. If a person is living on a property with a central heat pump HVAC system or a forced air system with substantial ductwork, he or she will need a bypass, steam, or fan-driven humidifier.

For larger homes, it’s best to choose a steam humidifier, while a fan-powered model is suitable for properties that have limited access to ductwork near the furnace. But, in this guide, we’ve discussed the installation steps for the most commonly available humidifier, called the evaporative bypass model.

Tip2 Most furnace-mounted humidifier manufacturers typically offer their products along with essential components and installation guides. Although based on what the humidifier box contains, if required, you may need to buy some further supplies, including a certain plumbing valve or an extended water supply pipe for your unit. The requirement of these materials may vary from brand to brand and model to model.

Tip 3 Ensure permit requirements, while in most scenarios, there is no need to obtain permission for such installation. Whatever the case, be sure to check with your local municipality before starting work.

How to install a humidifier on a furnace: A comprehensive guide!

Step 1 Choose the right location for installation

Begin by marking out your humidifier template on your duct. On the box of a whole house humidifier, there will be a cut-out for a hole to be drilled into your ductwork. Read the manual instructions carefully to determine which location would be best for the humidifier and its associated humidistat.

Homeowners are advised to locate a humidifier that has quick and easy reach to a drain and a water source.  Place the stencil in the final location and trace it using a marker on the return air duct or supply.

Step 2 Mark and Cut the hole

The next step is to remove the template, and you will need to make a hole on the traced edges. Use aviation snips to cut out the exact size you marked using the template from the duct.
Meanwhile, don’t forget to wear protective gear to make sure your skin and hands are away from unwanted mishaps. Now, utilize the screws that come inside the installation kit to attach the unit’s foam gasket and mounting plate to this hole.

Step 3 Mark the Humidistat location

In the third step, you will need to work with the humidistat, an essential component that lets you adjust a humidity setting as well as keep an eye on the airborne water substance.

Read the manufacturer’s guidelines to determine the right location of the humidistat. Usually, a humidistat is affixed to the cold air plenum, simply on the coming way of the air duct. Make sure this location is easily accessible. Again start outlining with the help of its template and cut out the holes for the humidistat.

Step 4 Place the Humidistat

If your whole house humidifier box doesn’t provide an integrated humidifier, you’ll need to assemble it separately. For installing the gasket and humidistat structure into the hole, you should use screws and bolts that come along with the installation kit.

If your unit calls for electrical power for the control panel or fan, be sure to connect it to a 24V transformer. While some models require regular manual wiring, most require plugging into an electric outlet. Therefore, if you are not sure how to work with electrical circuitry, seek help from an expert or a nearby electrician.

Instead, read the manufacturer’s instructions for proper wiring installation.

Bear in mind the wiring installation procedure may comprise an additional harness or external transform and will differ based on the model you opt for. If required, shut down the outlet or cut off the power to the furnace, and thoroughly follow the wiring movement for your particular humidistat unit. Before working with electrical components, test with a probe-type power tester to be sure the power to the circuit you’re working on is off.

Step 5 Mount the Humidifier

Follow the flow of wiring movements by connecting both wires to mount the humidistat to the humidifier. In case your humidifier features an external pressure switch, assemble that by making a hole with a drill and forming the connection using appropriate instructions.

Step 6 Install the drain line

Most humidifier boxes offer a drain line for releasing excess water. If your furnace has to, install a drain port and share the line. Make sure there is a drain on the bottom of your humidifier. Be sure to check the installation kit to locate the plastic tubing. If not available, you are advised to have fittings and PVC pipe for adequate drainage. Extend the pipe to the nearest condensate pump or floor drain.

Step 7 Add Water Supply line

Every humidifier usually uses hot or cold water. Assemble the water supply line provided with the model unit into the compression adjustment on the unit’s starting side of the humidifier. After that, fix it firmly with an adjustable wrench. Enlarge the water supply line to close to the water pipe.
Next, you’ll need to connect the supply line to the fitting of the saddle valve. Before starting work, make sure the valve is turned off. Then, pierce and securely fasten the saddle valve to the pipe. If case saddle attachments are notwithstanding the property code in your location, shut down the water supply throughout the property and place a tee fitting into the water supply line.

Step 8 Place the bypass vents (if needed/optional)

If a bypass vent is required, use the template to mark the hole for a six-inch bypass line. Start drilling at that location, make a starter hole, and cut the vent hole using aviation snips.
Next, place a round collar, using sheet metal screws to fasten it firmly in place. Check the exact distance between the collars and humidifier air inlet, and finally, cut the vent pipe to length. Place elbows on either end of the vent line. Finally, secure the assembly to the humidifier air intake and collar.

Step 9 Rearrange the humidifier

Turn on the power outlet and water source. Make sure the saddle valve is being opened. After completing the installation, check for any leaks around the connection. Be sure that the drain line is working appropriately. Finally, observe the humidity level within your property to make sure it is working as expected.


Installing a humidifier on a furnace requires some DIY expertise and skills. Before proceeding, make sure to read the manual instructions in each step. This is advisable because inappropriate installation can lead to water damage or create a potential risk throughout your property. For more installation and guidance regarding this, contact Smile HVAC.