Troubleshooting accessory installations

ecobee SmartThermostat with voice control, ecobee4 and ecobee3 support most common HVAC accessories such as humidifiers, dehumidifiers, and ventilators. Accessories can be wired as a 2-wire or 1-wire, depending on how the accessory has been set up with your system.

Ventilators usually come as 2-wire accessories, while humidifiers and dehumidifiers can be both.


1-wire accessories terminate at the ACC+ terminal on the ecobee, and utilize an existing 24V power source from the HVAC equipment to send the signal for the accessory to turn on. The 24V power will come from the Rc or Rh terminal depending on the configuration and model of the thermostat.


2-wire accessories are electrically isolated from the HVAC equipment and have their own power source to turn the unit on. When installing a 2-wire accessory, the wires can be terminated interchangeably on the ACC+ and ACC- terminals on the thermostat. The ACC+ and ACC- form a dry contact relay when configured as a 2-wire accessory.




Ventilator Wiring:


Configuring your accessory

The ecobee will ask for accessory configuration upon initial setup and you will be given the option of selecting a 2-wire or 1-wire configuration. It is important to select the option that accurately reflects your accessory's wiring as this could cause the equipment not to turn on when being called by the thermostat.


Humidifiers can be configured as evaporative or steam. Evaporative humidifiers require a heat source and will not turn on outside of a heating call because of this. Steam humidifiers, on the other hand, can run outside of a heating call since it is capable of adding moisture to the airflow on its own.

If you experience issues with your humidifier and are unsure of the type of humidifier you have, steam humidifiers utilize a steam canister to operate.

You can edit your humidifier's configuration by going to Main Menu > Settings > Installation Settings > Equipment > Humidifier.


Humidity Set point and Frost Control

To edit your humidifier's set point, go to Main Menu > System > Humidifier. Select ON to set a specific humidity set point for your thermostat.

Alternatively, you can select to activate Frost Control. With Frost Control enabled, the ecobee will automatically maintain the humidity to stay comfortable but prevent condensation or frost on your windows.

When Frost Control is enabled, the ecobee will automatically choose a humidity set point based on your Window Efficiency rating.

You can set your Window Efficiency by navigating to MAIN MENU > SETTINGS > INSTALLATION SETTINGS > EQUIPMENT > HUMIDIFIER > WINDOW EFFICIENCY. From there, select a value from 1 to 7, with 1 being the least efficient, and 7 being the most efficient.

The ecobee will ask for the relay state of your dehumidifier during the setup. The relay will be either open or closed, this information can be found on your dehumidifier owner's manual.

To edit your selection after the initial setup and to view other settings, go to Main Menu > Settings > Installation Settings > Equipment > Dehumidifier.

To set your desired humidity percentage for your dehumidifier, go to Main Menu > System > Dehumidifier.


Ventilators can be configured as a Standard Ventilator, Energy Recovery Ventilator or Heat Recovery Ventilator. It is important to select the correct option for your accessory as this will affect the way the ecobee will operate your equipment.

If you select the wrong ventilator type on initial configuration, you will need to return to the configuration setup at Main Menu > Settings > Installation Settings > Equipment > Reconfigure Equipment and select the correct ventilator type from there.


Energy Recovery Ventilator

ERVs are great for retaining heat and moisture in the air while maintaining steady airflow. You can configure your ERV's minimum runtime by going to Main Menu > System > Energy Recovery Ventilator.


Heat Recovery Ventilator

HRVs can be used to wick out excess humidity during winter months. You can toggle this feature by going to Main Menu > System > Heat Recovery Ventilator.


Standard Ventilator

On top of the Occupied/Unoccupied Min Runtime, standard ventilators have the additional feature of Free Cooling. This feature allows you to use your ventilator to cool down your house instead of the AC when the temperature outside is lower than the indoor temperature.

More settings and thresholds for Free Cooling can be found by going to Main Menu > Settings > Installation Settings > Equipment > Ventilator. See our Free Cooling feature article for more information on these thresholds.



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