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Guest Post: Installing a humidifier/dehumidifier to increase home comfort

by on November 7, 2014

The following is a guest blog post written by ecobee community member Brian Pratt. Let us know if you would like to write for the blog!

The ecobee3 smart thermostat can do more than control your heating and cooling. It was built with additional HVAC accessories in mind, such as humidifiers, dehumidifiers, ventilators, and HRVs or ERVs. In a dry climate, such as the one where I live, it is common to have a whole-house humidifier to increase the relative humidity in the home and increase comfort. Humidifiers often come with their own controllers, but the ecobee3 can help optimize your home’s comfort by bringing more “smarts” to the table.

There are a couple of things to keep in mind when selecting and setting up a whole-house humidifier with your ecobee3: whether the humidifier is an evaporative or steam model (the ecobee3 supports both), and the type of connection used (the ecobee3 supports the two most common types). I’ll give a bit of detail on both of these topics to help you understand the differences and how the ecobee3 can help optimize the humidity in your home.

There are two main types of humidifiers available: evaporative and steam. During the guided setup, ecobee3 asks you which type of humidifier you have. But, what exactly is the difference between the two? An evaporative humidifier is one that relies on the heat from your furnace to warm the air enough to evaporate the water flowing through the humidifier, thus adding humidity to the air flowing through your home. The ecobee3 is smart enough to only activate this type of humidifier during a call for heat. A steam-based humidifier is one that heats the water on its own and does not rely on the furnace. The ecobee3 knows that this type of humidifier can be used to increase the humidity (and comfort) of the home at any time, even if the heat is not running.

ecobee3 uses ACC+/ACC- terminals to control a humidifier (or another indoor air quality accessory). During installation, you are asked to specify if you have 2 wires at the thermostat for the humidifier (“externally powered”) or 1 wire (“internally powered”). If you don’t have wires run up to the thermostat yet, here’s the difference between the two (this should help you decide how to set things up): For an externally powered humidifier, the ecobee3 does not need to send power to the device. What it does is connect its own ACC+/ACC- terminals to each other (closed circuit) to let a 24V signal pass though them to activate the humidifier, and disconnects them (open circuit) when the humidifier should be turned off. The internally wired option works by the ecobee3 applying power (from the 24V R terminal) to the ACC+ terminal when humidity is desired and applying no power otherwise.

If you don’t have a humidifier in your house already, here are a few that are popular with ecobee3 owners and have great reviews:

The Aprilaire 500M or the Aprilaire 600M

These are both “evaporative”humidifiers. Note that, with the ecobee3 in control, you can get the 500M or 600M model rather than the more expensive 500 or 600 models that include an automatic controller. The ecobee3 will take control for you, no problem!

The Aprilaire 800

This is an example of a “steam”humidifier, which heats up the water itself and can humidify without the furnace running.