Nest Learning Thermostat (Gen 4) and Smart Ventilation: Setup and Config?

[teddymarinaro]

I've been looking forward to the new Gen 4 Learning Thermostat especially for the compatibility with home ventilation systems, but I don't know the wiring setup for it as I would be adding a separate system to my existing HVAC setup. 

Currently I've got a forced air system with a gas furnace and standard large-compressor AC unit on five wires of a seven wire setup as such:
C - 24v Common
Rh - Power
W1 - Heat
Y1 - Cool
G - Fan

I'm looking at the AprilAire 8145 (but will happily take other suggestions) and want to know what's the best home ventilation solution so I can bring in cool night air to my well-insulated home at night rather than use all that energy with my AC unit. 

Thoughts?

[ovidioj]

Hello @teddymarinaro,

Thanks for posting in the community.
I appreciate your interest in the Nest Learning Thermostat and home ventilation. To provide tailored assistance, please share the following information:

• HVAC System Details: Specify your HVAC system's make and model.
• Below you will find the information how it has to be connected: 

For specific guidance on compatibility and wiring instructions for the AprilAire 8145, I recommend contacting AprilAire's support team.

I'm here to assist you further if needed.

Regards, 
Jorge

[teddymarinaro]

Hey Jorge, this will be an addition of a ventilation system to the current HVAC system, but I was hoping to use the new Nest Learning Thermostat 4th Gen rather than wire it through the HVAC which doesn't look like it then integrates into it. Since the panel you're showing looks like the older system with only 10 wire controls, do you have access to the new information? I haven't been able to find anything on wiring diagrams for the 12-wire system that I have wired thusly:

[AxelD]

Hi Teddymarinaro,

Thanks for replying! I apologize that the diagram provided was for the previous generation. So far, I'm not able to provide the diagram for the new generation. However, checking your HVAC system specifications, it seems you own a conventional system. You'll find the exact same spots on the Nest Learning Thermostat 4th Gen as the ones indicated in the image above. Please give a try to that wiring configuration. 

Here is a video about how to install and set up the Nest Learning Thermostat (4th gen).

Let me know how it works.

Regards, 

Axel.

[teddymarinaro]

Hey Axel,

I do have a conventional system and that's all wired up and good to go. Heck, it's running better under the Gen4 than it did under the Gen3. The issue is that I've wanted to install a smart ventilation system that brings in cooler outside air rather than uses AC to cool what's already inside. Given that this was touted as one of the marquee features of the new thermostat, I was hoping for better direction on how to integrate that so I can start looking for a compatible system to install at my home.

The issue is that, for the moment, most systems run independent of any thermostat and instead have a timer to just refresh the air from time to time, or maybe have a secondary wall box to schedule this. I was hoping to use the smart ventilation features touted on the Gen4 to control this, but there's nothing available online that tells me how to wire that or even what the specific wire connection would be so I can start building out the wiring diagram myself. I know other systems have a means of just attaching one or two wires to the ventilator to turn on and off, I really just need to know how to add that on to the system or if it's done in another way.

Appreciated,

Jonathan

[AxelD · Accepted solution]

Hi teddymarinaro,

Thanks for replying! I appreciate the new details you gave me. It helps me to better understand the situation. I did some research about this situation. If your new ventilation system has only one wire, you can use the AQ+. If it has two wires, you can use the AQ- Spot. It's recommended to gather the ventilation system's wiring specifications to check compatibility with the Nest Learning Thermostat 4th Generation.

Regards,

Axel.

[teddymarinaro]

That's exactly what I wanted to know. I'll update this article post-install!

[Dmms15]

I’m literally installing the same system and have the same question. 

were you able to figure it out?

[teddymarinaro]

So, looking at the manual found here:
https://assets.unilogcorp.com/267/ITEM/DOC/Aprilaire_8145NC_Instruction_Installation_Manual.pdf

There's a couple ways of doing it. It looks like it wants its own controller to understand when the heat/cool cycles of the normal HVAC are going on so it can instead push the same with its air handler on a timer like a normal non-smart thermostat.

What I think we should try to do is wire it directly to the Nest using figure 16 as a guide as that would give us the VENT wires without the need to use any of their thermostat controls. This way should allow the Nest to control the AprilAire system whenever it needs to bring in fresh air without any needless negotiation between it and whatever controller/thermostat AA supplies or has you buy.

This is merely a guess based on the wiring diagram, however, and make sure to keep the other wires from the AA capped as you don't need supplied power from the AA as well.

[AxelD]

Hi teddymarinaro,

Thanks for replying and keeping me updated about your situation! If you already have an idea about how to wire it, try it and let us know how it works. Remember to use the spots indicated in my reply above.
 

Keep me posted.
 

Regards,
Axel.

[Twennywonn]

Axel can you chime in with the specific controls available to Nest 4th generation users when using it with a ventilation system?

Im personally looking for control to not ventilate when the temperature or humidity is really high or low.  

I would also like the system to be smart enough not to ventilate when the outdoor AQI is high from lets say a forest fire.  

Do we have the ability to run ventilation manually through the app like we can with fan?

In addition I would like Nest to lean on ventilation when the outdoor air is cooler then the setpoint in AC mode to get "free cooling".  

Screen shots of documentation of these features would be great.  

[Twennywonn]

Did you hook your nest up to your ventilation system?

I'm have an Aprilaire 8145 fresh air ventilator to my system and am trying to decide whether to control it with the Aprilaire thermostat or my Nest thermostat. The 8145 has features to disable ventilation if it's too humid, too hot, or too cold. I'd like to confirm that the Nest thermostat offers similar functionality and allows me to set my own parameters.

I've also heard that the Nest can use the ventilation system to cool the house by bringing in cooler outdoor air, potentially reducing the need for AC. Additionally, I've read that the Nest won't activate the ventilation system if the outdoor AQI is poor. Could anyone share a screenshot of the available ventilation options on the Nest thermostat?

Google doesn't seem to share these options or settings anywhere.   I want to make sure the Nest is more capable than the Aprilaire controller.  

[teddymarinaro]

I haven't yet, having to spec out the addition right now but it looks like I'll be going forward with it soon.
I would ask @AxelD about the functionality as I saw that too without having any actual documentation to back that up. If there's anything solid you're able to find, please let me know as reducing AC use is the exact reason why I'm looking to do this.

[AxelD]

Hi everyone,

Thanks for your replies and updates! Unfortunately, I couldn't find any specific backup or guide on wiring a ventilation system. I recommend contacting a Nest Pro for professional assistance with the installation process. They're experts in this area and can provide the best guidance.

Best regards,

Axel.

[Twennywonn]

Axel this is an unacceptable answer.   I know how to hook up my ventilator to the Nest thermostat.   What I want to know is what kind of control does the Nest provide over my ventilator.     Temp limits, humidity limits etc.   This is simple information that you have to access to.