Nest 3 & humidiier - power draw; outside temp; fan-only mode questions

[JeffW4]

I have a Nest 3, looking to install an Aprilaire 600 on my HVAC, and have the Nest control the humidity level.  A few questions:

1. Can the * terminal on the thermostat be directly connected to the humidifier?  Aprilaire says the solenoid for the water valve draws 0.5A when it's in on (humidify) mode.  Can the Nest supply that level of current?  It would be easier if I could just connect it directly.  I know the alternative is to have the * be connected to the control line of a relay, vs directly powering it.   I thought I saw where the Nest was rated for over 1A, so maybe it could be sufficient.

2. Does the Nest factor in the outside temperate (which it has via the internet) to dial down the humidity when it gets cold out?   I've had previous Aprilaire installs where I used their AutoStat (ie. Aprilaire 600A model) with it's outside temperature probe.  That was pretty effective at auto-adjusting for colder weather.

3. Just confirming, the "on" mode of the humidifier in the Nest can be setup to either run when the heat is on ("heat+fan" mode), or also "fan only" mode, where it will turn on the fan (and the humidifier) if it needs to add humidity?   The Aprilaire humidistat/autostat had that option, which I used.   Glad to see (if confirmed) the Nest also has that.

Thanks.  Jeff

[GabrielaG]

Hi JeffW4,

Thanks for reaching out to the community. I am aware that you would like to know if the Nest Learning thermostat is compatible with the Aprilaire 600 HVAC system. I will be happy to assist you right now.

Most dehumidifiers and humidifiers that operate separately from your air conditioner can be used with Google Nest Learning Thermostats. However, it is highly advised to have the installation done by an expert.

To learn more about Nest thermostats and humidifiers, you can refer to these articles. Humidifier and dehumidifier compatibility and Nest thermostat technical specifications. 

 Feel free to keep us posted if you have more questions.

Regards,

Gabriela

[JeffW4]

Gabriela,

  Thanks for replying to me.

  At this point, all I need are the technical answers to my questions above, the answers which I haven't been able to find elsewhere on Nest official documentation (including the links you provided).  After receiving the information, then I can decide if the installation is above my level of experience.

Jeff

[GabrielaG]

Hi JeffW4,

Thank you so much for keeping me updated. It will be my pleasure to answer your questions.

1. Can the star terminal on the thermostat be directly connected to the humidifier? 

The Nest Learning Thermostat is not designed to directly power a humidifier. The star terminal is designed to control a relay, which in turn powers the humidifier.

Even though the thermostat manufactured by Nest is rated for more than one amp, it is not suggested to attach the humidifier directly to the star port. This may damage the thermostat or cause a safety risk.

2.Does the Nest factor in the outside temperature (which it has via the internet) to control the humidity when it gets cold out? 

With Cool to Dry, Google Nest thermostats can use your air conditioner or heat pump to help reduce excessive humidity in very humid climates. This humidity control helps to prevent mold and maintain a healthier environment in your home. If your air conditioner has a dehumidification mode, your Nest thermostat can do even more to help reduce your home's humidity. You can refer to this article to learn about Cool to Dry.

3. The "on" mode of the humidifier in the Nest can be set up to either run when the heat is on ("heat + fan" mode) or also "fan only" mode, where it will turn on the fan (and the humidifier) if it needs to add humidity. 

 "Fan Only": This option allows the humidifier to operate independently of the heating system. This can be helpful when you need to enhance humidity but don't want to put on the heat. You can refer to this article, Fan Control with a Nest Thermostat, to learn more about it.

 Feel free to keep us posted if you have more questions.

Best regards,

Gabriela