How to Install a Whole-House Humidifier

Knowing how to install a whole-house humidifier requires some technical knowledge and skill. However, the effort is well worth it: in the cold, dry months of winter, a humidifier can improve your indoor air quality and help you feel a lot more comfortable. So keep reading to learn the key steps of a successful humidifier installation, from ductwork to water lines to electrical.


Let’s start with the ductwork. We’re going to put the unit on the return, and then we’re going to duct it over to the supply.

  1. First things first: you’ve got to cut a hole into the return. This is where we’ll mount the humidifier unit.
  2. You now can mount the unit on the hole. A couple of pointers here: a) make sure that it stays nice and level so that when the water drains, it goes down the drain and not out the sides; b) put some foam backing on around the edges of the hole to keep it airtight.
  3. Now that the unit’s installed, it’s time to run the duct work from the humidifier to the supply line.

Water lines

Once the ductwork is up and connected, you’re ready to work on the water line.

  1. First, you’ll want to turn off the water, and drain the pressure from the lines to prevent any spills.
  2. Next, it’s time to connect the humidifier to a supply line. The method, however, depends on what type of pipe you’re working with. In our video example above, the unit comes with what’s called a “saddle valve” — but this will only work on a copper pipe. If your home has PEX pipe, a saddle valve will not work, as it will result in leaks.
  3. Connect the humidifier’s water line to the home’s hot water line. The humidifier works better with hot water, so avoid connecting it to the cold water line.
  4. Now that you’ve got your supply line connected, now you’ve got to do the drain. The drain is going to connect to the furnace condensate pump, to get rid of excess water.


Now you’re ready for the electrical. It’s a very simple circuit, and the humidifier should come with a transformer.

  1. In our example, you wire the high voltage off the control board and the Electronic Air Cleaner. This way, when the fan turns on, it’ll power up our humidifier. After hooking up the high voltage, you power the solenoid valve with your thermostat.
  2. A note about the electrical wiring: although it’s simple, it can be a bit frustrating. Follow the instruction manual for help. You’ll find some good diagrams on how to finish this part of the task.
  3. Now, if necessary, you install the humidistat. In our example, the home’s thermostat already has the ability to control humidity. But if your thermostat can’t do that, then you need to install the supplied humidistat. The instruction manual should provide a breakdown on how to do the wiring. You’ll need to install the transformer to a 120-volt power source, and then connect the wires of the digital humidistat controller into the furnace. All of the thermostat wires are going to stay the same, except for the green wire, which controls the fan. If your humidifier kit comes with an outdoor temperature sensor, it’s a good idea to install it: it will control the humidity a little more accurately.

Final steps

All right, we’ve got our duct work done, we’ve got our water lines in and out, and we’ve done the electrical. Now it’s time to put the unit back together.

First, put the water line through the hole until it hits the stopper. That’s how you know that you’ve got it in the right direction. Pop that together, put the cover on, and you’re ready to test the unit. Make sure that you switch the mode to the right season, then test out the thermostat to make sure it recognizes the humidifier. If it does, then you’re all done!

If you need further help with your heating and cooling system, don’t hesitate to give us a call. And subscribe to our YouTube channel for more helpful videos!

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