Nest 4th Gen Fresh Air Ventilation

[cezarp]

Hi! I just a bought a new 4th Gen Google Nest Thermostat. I replaced my 3rd generation one with the 4th because the AC technician told me that only the 4th gen can control the "Fresh Air" feature, but, after replacing it and plugging the wiring, I still can't see the "Fresh Air" option when the app asks me what is the "*" wiring intended for. The only options available are "Humidifier", "Dehumidifier" and "I don't know".

So, what do I need to do in order to see the "Fresh Air" option inside the "What's connected to the (*) terminal"?

Thanks

[EvaMendex]

Did you manage to make it work for controlling fresh air?
I’m also curious if this 4th gen Nest can really help with keeping the air fresh and humidity under control. A mold removal company actually recommended installing a device like this so mold doesn’t come back, but I’m not sure if it’s the right setup.

[cezarp]

No, not yet. But in case I find a solution I'll let you know.

👊

[cezarp]

Yeah! With the latest response I was able to configure the 4th gen nest to control the ventilation system.
I'm not sure if it is working, but I guess it is.

[EvaMendex]

That’s great to hear! I’m thinking about trying this for my home too, mainly to keep the air fresh and prevent mold. Thanks for sharing!

[moralesvicente]

Hello folks,

Thank you so much for posting in this community. I understand that you have questions about whether the Nest Learning Thermostat 4th gen has the "Fresh Air" feature. After replacing it and plugging in the wiring, this feature is not showing up on the app, and it’s asking you what the star cable wiring is intended for. No worries, it’s a pleasure to help you.

In this case, the Nest Learning Thermostat 4th gen has a Smart ventilation feature. To use it, you must connect your ventilation system to the AQ+ and AQ- terminals on the Nest Thermostat's backplate, depending on your wiring system. These are the specific terminals for a ventilation accessory. With the correct wiring, the Smart ventilation option will be available in the Settings menu. For more information, refer to this article: Set up ventilation on your Nest Learning Thermostat (4th gen). You can also visit our Help Center to learn more about Nest thermostat compatibility.

The star terminal on your Nest Learning Thermostat 4th gen is designed to manage different system functions. Depending on your home's setup, a wire connected to this terminal can control a humidifier, dehumidifier, or even activate emergency heating. To learn more details, check out this guide: Nest thermostat star terminal.

Let me know if you have more questions.

Best regards,

Daniel

[cezarp]

Thanks for your reply, but the problem is that I have only ONE wire, not two,

How to proceed?

[moralesvicente]

Hey cezarp, 

Thank you so much for keeping me updated. Regarding your question, if you have a 1-wire ventilation system, you can connect it solely to the AQ+ terminal with no wire in AQ-. This means that the thermostat provides power to the ventilation system by shorting R to AQ+.

Let me know how it goes. 

Regards, 

Daniel

[cezarp]

I plugged the wire that was on the star (*) to AQ+, then I had to go the system and set AQ+ to Ventilation. I'm not sure if it is working, but I guess it is.

Is there a way I can tell if the ventilation/fresh air system is indeed working on nest?

Thanks for the tips!

[moralesvicente]

Hi cezarp, 

Thanks for your reply. To verify if this feature is properly configured in your thermostat, follow the next steps:

• On your physical thermostat, go to Settings, then Equipment. You'll find your current wiring configuration and ensure all the cables have been detected.
• Check if you have the option Smart Ventilation available. On the Google Home app, tap your thermostat, select Settings, then Ventilation and switch to enable it. If so, it means that the configuration has been successfully applied.

Let me know if you have more questions.

Regards, 

Daniel

[jeny78]

Thanks for sharing this discussion! Integrating fresh air ventilation is such a smart move for indoor air quality, especially in tight bathroom spaces. In fact, during my own bathroom remodel in Arvada, CO, I made sure to plan for adequate ventilation, humidity control, and airflow before finalizing finishes. Getting those systems right early really helps prevent long-term issues like mold or stale air.
Looking forward to seeing what solutions you choose!