How To Wire Humidifier To Furnace: Find Out Now

  • Time to read: 7 min.

The furnace is probably one of the most important appliances inside a home. It provides warmth through hot air circulation which is highly crucial during the cold months. In the US, the coldest temperatures are felt in December, January, and February.

Apart from the freezing temperature during these months, one often experiences dry indoor air making the living spaces less comfortable and may worsen some respiratory and skin diseases.

While the furnace provides warmth through the cold season, it cannot still solve the latter problem and provide air moisture or humidity. Thankfully, installing a humidifier on the furnace is a handy solution to this problem.

A humidifier delivers moistened air throughout the house. The added moisture in the air makes the house more comfortable and can also help make the house feel warmer at the same time. All these benefits while still consuming the same energy. Great, isn’t it? Well, it gets even better. The installation and wirings of the humidifier can also be done as a DIY project so you can save money on labor costs. 

Wiring a humidifier to the furnace control board doesn’t have to be complicated. But you need to remember that this task requires attention to detail and time. Humidifiers vary from each other so you have to remember to read and follow the instructions in your manual accordingly to find out the proper wirings. 

Read on as we get into the different steps of how to wire humidifiers to the furnace in more detail. 

Components and Tools needed for wiring

Before we begin, you have to first prepare the following components and tools.

  • Furnace Humidifier 

A furnace humidifier is installed into the furnace or HVAC system. This humidifier is known for its low maintenance and easy usage.

There are three types of furnace humidifiers namely: flow-through humidifiers, reservoir types, and steam humidifiers.

  1.  Flow-through humidifier. It works by exposing the furnace’s warm air to the flow of water through the system. The water evaporates into the air and exits the furnace.
  2.  Drum humidifier. It uses a reservoir of water and a rotating belt passes through the water reservoir resulting in a moistened belt. The belt moisture evaporates into the air and leaves the furnace.
  3.  Steam humidifier. It functions by heating the water to produce steam. The steam is then distributed accordingly.

All these humidifier types are viable options but the flow-through humidifier is the most common type of furnace humidifier in many households. This is probably because they are generally low maintenance and more hygienic. They are also more budget-friendly and only consume relatively less electricity compared to other humidifier types.

  • Humidistat

A humidistat or hygrostat functions by controlling the humidity levels of the house. This small device can measure the humidity levels and adjust the humidity levels accordingly. Typically, it is included in the furnace humidifier package.

  • 18-2-voltage wire

The 18-2 voltage wire will be used for connecting wires. This wire is not included in the humidifier package and you have to buy it yourself.

  • 24-volt wire

The 24-volt will also be used for connecting the furnace to the humidistat. Oftentimes, it is included in the furnace humidifier package,

  • Pliers 

Prepare pliers for stripping and cutting the wires. You can use any type of pliers but the needle-nose pliers are the most suitable for wiring a humidifier to the furnace.

  • Screwdrivers

Use the screwdriver for screwing or unscrewing wire cases or installing wires on the control.

Step-by-step guide on how to wire a humidifier to the furnace

Wiring should follow after installing the humidifier. You should also be able to install the humidistat accordingly before wiring. Some modern thermostats can control the humidity level. If your thermostat can control the humidity level, then you may not need a humidistat. You may also need to install a transformer depending on the humidifier you have or your preference.

After installing all the components, you can proceed to the steps below for wiring.

Step #1. Turn off your furnace

Always remember to prioritize your safety and work with an inactive heating system. You can turn off the furnace by simply turning off its power switch. However, turning it off directly at the circuit breaker is highly encouraged as it can ensure that no electricity will flow to the furnace as your work.

Step #2. Identify the electrical terminals for wiring

Look for the electrical terminals on your humidistat and furnace control board. Two terminals will connect to the humidistat and another two will connect to the furnace control board. 

A wiring diagram should be provided on the humidistat or humidifier instructions. Furnaces and humidifiers vary by brand and model so always study the diagram first before wiring

Depending on the manual instructions, you will be using an 18-2 low voltage wire for wiring so keep it near beforehand.

Step #3. Connect the sensing bulb wire

Your sensing bulb should be installed outside of your hour house. Connect the sensing bulb wire to the humidistat using an 18-2 low voltage wire.

Connect the wires to the humidistat control where it says outdoor temperature sensor or ODT. Always follow the labels for easy wiring.

Step #4. Hook up the 24-volt wire from the humidistat to the furnace

On the furnace control board, you will see a terminal named HUM, or humidifier. Connect the 24-volt wire from the humidistat on the HUM terminal of the furnace

Step #5. Connect the 24-volt water solenoid wire to the furnace control board

Hook up a 24-volt wire to the humidistat to connect the water solenoid sensor. Connect the other end of the wire to the humidistat terminal labeled with AA.

Step #6. Review the provided wiring diagram and double-check your wiring

The key to a successful humidifier to furnace wiring is following all the instructions and the wiring diagram properly. As we have briefly tackled before, humidifiers vary from each other so following their particular manual is highly crucial.

In addition, remember to double-check if all your wirings are secure. They don’t have to be too tight but they do need to be securely connected to the terminals.

Safety precautions when wiring humidifier to the furnace

Wiring a humidifier to the furnace is generally a safe task to do, however, you still need to observe safety precautions to avoid any mishaps. Below are some safety precautions you can follow.

  • Turn off the furnace

Wiring deals with electricity so always make sure that there is no electricity or power flow when you are working.

  • Use gloves and wear footwear

Gloves can protect you from any possible electric shocks. On the other hand, the bottom of footwear acts as an insulator and prevents you from having contact with the ground. If you happen to touch a live wire while wearing footwear, you will not get a shock.

  • Be careful of what you touch

Wirings can be confusing and one small move can ruin them. Always be mindful of what you are touching or moving inside the control box.

  • Use the right tools

Don’t use alternative tools for wiring. Only use appropriate tools like pliers and screwdrivers.

  • Don’t just guess and connect wires carelessly

Appliances like a humidifier come with a manual for a reason. That reason is to guide you to connect the wires accordingly and avoid any guessing or carelessness in hooking up wires.

Helpful Tips

If you opt to install a transformer to convert power remember to always follow the manual. Usually, here are the steps you need to follow for installation and wiring.

  1.  Install your transformer into your electrical box for a constant power source. The power source typically requires 120v of constant power. Always check your transformer specification.
  2.  Identify the input and output wires. The input wire should be connected to the power source. The output wire should be connected to the humidifier.
  3.  Seal any exposed wirings with electrical tape.

For safer and more organized wiring management, run the wiring inside the ductwork or use a flexible conduit to contain them and prevent any access.

Don’t run your wiring anywhere near sharp objects. Sharp objects can damage your wiring and expose the conductors inside which may cause electrocution.

Make it a habit to read the labels before connecting any wires. This will give you an easier time identifying and locating the terminals in the control board.

Research before wiring. You will be surprised by how simple information can make a difference in doing new tasks for you. If you are not sure where to start or the manual just simply confuses you, don’t be hesitant to research more for more information.

Final thoughts

Wiring is an essential part of installing humidifiers in your home. Humidifiers usually come with a humidistat and sometimes a transformer. A humidistat is important for measuring and adjusting humidity levels.

On the other hand, a transformer allows you to convert high power to the amount of power needed for the humidifier. Depending on your preference and need, you may opt not to install the transformer.

Humidifier wirings are done in the humidistat. The wirings may vary from one humidifier to another. Hence, always remember to check the manual and wiring diagram beforehand. In addition, don’t forget to observe safety precautions while wiring and pay attention to details.